viewpager与缩放效果的photoview的联合使用

最近用到点击查看图片详情，要求图片可以缩放且旋转。
主要代码如下，gridview的onItemClick点击事件，
@Override
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
    // TODO Auto-generated method stub  if (imageUrl!=null) {
        Intent intent=new Intent(context,ImgGalleryActivity.class);
        //将所有图片结合 和被点击的图片位置传到ImgGalleryActivity中  intent.putStringArrayListExtra("imageUrl", (ArrayList<String>) imageUrl);
        intent.putExtra("pos", arg2);
        App.gotoActivity(context, intent);
    }
}
ImgGalleryActivity代码如下：

package cn.doolii.shopping.activity.shops;


import java.util.ArrayList;
import java.util.List;


import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;

import cn.doolii.shopping.R;
import cn.doolii.shopping.utils.ImageLoaderUtils;
import cn.doolii.shopping.view.PhotoView;
import cn.doolii.shopping.view.RotateDownPageTransformer;

public class ImgGalleryActivity extends Activity {
   private ViewPager mPager;
   private Context context;
   String[] imgsList;
   private int pos;//传过来的 点击图片位置  @Override
   protected void onCreate(Bundle savedInstanceState) {
      requestWindowFeature(Window.FEATURE_NO_TITLE);
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_img_gallery);
      context=this;
      Intent intent=getIntent();
      if (intent!=null) {

         imgsList=intent.getStringArrayExtra("imgsList");
         pos=intent.getExtras().getInt("pos");
         if (imgsList!=null&&imgsList.length>0) {
            mPager=(ViewPager)findViewById(R.id.pager);
            //设置图片之间的距离 // mPager.setPageMargin((int) (getResources().getDisplayMetrics().density * 15));   mPager.setAdapter(new PagerAdapter() {
               @Override
                  public int getCount() {
                      return imgsList.length;
                  }

                  @Override
                  public boolean isViewFromObject(View view, Object object) {
                      return view == object;
                  }

                  @Override
                  public Object instantiateItem(ViewGroup container, int position) {
                      PhotoView view = new PhotoView(context);
                      view.enable();
                      
// Bitmap bitmap=ImageLoaderUtils.ImageLoader(context, url.get(position), view);  ImageLoaderUtils.ImageLoader(context,imgsList[position], view);
// view.setImageResource(imgsId[position]);  //设置为被选择的图片 // mPager.setCurrentItem(pos);  container.addView(view);
                      return view;
                  }

                  @Override
                  public void destroyItem(ViewGroup container, int position, Object object) {
                      container.removeView((View) object);
                  }
              });  

		//根据传过来的pos viewpager中显示第pos张图片  
            mPager.setCurrentItem(pos);
            //viewpager 的切换动画 RotateDownPageTransformer是自定义的  mPager.setPageTransformer(true,new RotateDownPageTransformer());         
         } 
      }
   }
}

xml文件如下：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"  xmlns:tools="http://schemas.android.com/tools"  android:layout_width="match_parent"  android:layout_height="match_parent"  android:background="#000000"  android:fitsSystemWindows="true">
<android.support.v4.view.ViewPager  android:id="@+id/pager"  android:layout_width="match_parent"  android:layout_height="match_parent"   />

</RelativeLayout>
用到的类PhotoView代码如下：

package cn.doolii.shopping.view;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.graphics.RectF;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewParent;
import android.view.animation.DecelerateInterpolator;
import android.widget.ImageView;
import android.widget.OverScroller;
import android.widget.Scroller;

/**  * Created by liuheng on 2015/6/21.  * <p></p>  * 如有任何意见和建议可邮件 [email protected]  */ public class PhotoView extends ImageView {

    private final static int MIN_ROTATE = 35;
    private final static int ANIMA_DURING = 320;
    private final static float MAX_SCALE = 2.5f;
    private int MAX_OVER_SCROLL = 0;
    private int MAX_FLING_OVER_SCROLL = 0;
    private int MAX_OVER_RESISTANCE = 0;
    private int MAX_ANIM_FROM_WAITE = 500;

    private Matrix mBaseMatrix = new Matrix();
    private Matrix mAnimaMatrix = new Matrix();
    private Matrix mSynthesisMatrix = new Matrix();
    private Matrix mTmpMatrix = new Matrix();

    private RotateGestureDetector mRotateDetector;
    private GestureDetector mDetector;
    private ScaleGestureDetector mScaleDetector;
    private OnClickListener mClickListener;

    private ScaleType mScaleType;

    private boolean hasMultiTouch;
    private boolean hasDrawable;
    private boolean isKnowSize;
    private boolean hasOverTranslate;
    private boolean isEnable = false;
    private boolean isInit;
    private boolean mAdjustViewBounds;
    // 当前是否处于放大状态  private boolean isZoonUp;
    private boolean canRotate;

    private boolean imgLargeWidth;
    private boolean imgLargeHeight;

    private float mRotateFlag;
    private float mDegrees;
    private float mScale = 1.0f;
    private int mTranslateX;
    private int mTranslateY;

    private float mHalfBaseRectWidth;
    private float mHalfBaseRectHeight;

    private RectF mWidgetRect = new RectF();
    private RectF mBaseRect = new RectF();
    private RectF mImgRect = new RectF();
    private RectF mTmpRect = new RectF();
    private RectF mCommonRect = new RectF();

    private PointF mScreenCenter = new PointF();
    private PointF mScaleCenter = new PointF();
    private PointF mRotateCenter = new PointF();

    private Transform mTranslate = new Transform();

    private RectF mClip;
    private Info mInfo;
    private long mInfoTime;
    private Runnable mCompleteCallBack;

    private float[] mValues = new float[16];

    public PhotoView(Context context) {
        super(context);
        init();
    }

    public PhotoView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public PhotoView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init() {
        super.setScaleType(ScaleType.MATRIX);
        if (mScaleType == null) mScaleType = ScaleType.CENTER_INSIDE;
        mRotateDetector = new RotateGestureDetector(mRotateListener);
        mDetector = new GestureDetector(getContext(), mGestureListener);
        mScaleDetector = new ScaleGestureDetector(getContext(), mScaleListener);
        float density = getResources().getDisplayMetrics().density;
        MAX_OVER_SCROLL = (int) (density * 30);
        MAX_FLING_OVER_SCROLL = (int) (density * 30);
        MAX_OVER_RESISTANCE = (int) (density * 140);
    }

    public static int getDefaultAnimaDuring() {
        return ANIMA_DURING;
    }

    @Override
    public void setOnClickListener(OnClickListener l) {
        super.setOnClickListener(l);
        mClickListener = l;
    }

    @Override
    public void setScaleType(ScaleType scaleType) {
        ScaleType old = mScaleType;
        mScaleType = scaleType;

        if (old != scaleType)
            initBase();
    }

    public void enable() {
        isEnable = true;
    }

    public void disenable() {
        isEnable = false;
    }

    /**  */  public void setMaxAnimFromWaiteTime(int wait) {
        MAX_ANIM_FROM_WAITE = wait;
    }

    @Override
    public void setImageResource(int resId) {
        Drawable drawable = null;
        try {
            drawable = getResources().getDrawable(resId);
        } catch (Exception e) {
        }

        setImageDrawable(drawable);
    }

    @Override
    public void setImageDrawable(Drawable drawable) {
        super.setImageDrawable(drawable);

        if (drawable == null) {
            hasDrawable = false;
            return;
        }

        if (!hasSize(drawable))
            return;

        if (!hasDrawable) {
            hasDrawable = true;
        }

        initBase();
    }

    private boolean hasSize(Drawable d) {
        if ((d.getIntrinsicHeight() <= 0 || d.getIntrinsicWidth() <= 0)
                && (d.getMinimumWidth() <= 0 || d.getMinimumHeight() <= 0)
                && (d.getBounds().width() <= 0 || d.getBounds().height() <= 0)) {
            return false;
        }
        return true;
    }

    private int getDrawableWidth(Drawable d) {
        int width = d.getIntrinsicWidth();
        if (width <= 0) width = d.getMinimumWidth();
        if (width <= 0) width = d.getBounds().width();
        return width;
    }

    private int getDrawableHeight(Drawable d) {
        int height = d.getIntrinsicHeight();
        if (height <= 0) height = d.getMinimumHeight();
        if (height <= 0) height = d.getBounds().height();
        return height;
    }

    private void initBase() {
        if (!hasDrawable) return;
        if (!isKnowSize) return;

        mBaseMatrix.reset();
        mAnimaMatrix.reset();

        isZoonUp = false;

        Drawable img = getDrawable();

        int w = getWidth();
        int h = getHeight();
        int imgw = getDrawableWidth(img);
        int imgh = getDrawableHeight(img);

        mBaseRect.set(0, 0, imgw, imgh);

        // 以图片中心点居中位移  int tx = (w - imgw) / 2;
        int ty = (h - imgh) / 2;

        float sx = 1;
        float sy = 1;

        // 缩放，默认不超过屏幕大小  if (imgw > w) {
            sx = (float) w / imgw;
        }

        if (imgh > h) {
            sy = (float) h / imgh;
        }

        float scale = sx < sy ? sx : sy;

        mBaseMatrix.reset();
        mBaseMatrix.postTranslate(tx, ty);
        mBaseMatrix.postScale(scale, scale, mScreenCenter.x, mScreenCenter.y);
        mBaseMatrix.mapRect(mBaseRect);

        mHalfBaseRectWidth = mBaseRect.width() / 2;
        mHalfBaseRectHeight = mBaseRect.height() / 2;

        mScaleCenter.set(mScreenCenter);
        mRotateCenter.set(mScaleCenter);

        executeTranslate();

        switch (mScaleType) {
            case CENTER:
                initCenter();
                break;
            case CENTER_CROP:
                initCenterCrop();
                break;
            case CENTER_INSIDE:
                initCenterInside();
                break;
            case FIT_CENTER:
                initFitCenter();
                break;
            case FIT_START:
                initFitStart();
                break;
            case FIT_END:
                initFitEnd();
                break;
            case FIT_XY:
                initFitXY();
                break;
        }

        isInit = true;

        if (mInfo != null && System.currentTimeMillis() - mInfoTime < MAX_ANIM_FROM_WAITE) {
            animaFrom(mInfo);
        }

        mInfo = null;
    }

    private void initCenter() {
        if (!hasDrawable) return;
        if (!isKnowSize) return;

        Drawable img = getDrawable();

        int imgw = getDrawableWidth(img);
        int imgh = getDrawableHeight(img);

        if (imgw > mWidgetRect.width() || imgh > mWidgetRect.height()) {
            float scaleX = imgw / mImgRect.width();
            float scaleY = imgh / mImgRect.height();

            mScale = scaleX > scaleY ? scaleX : scaleY;

            mAnimaMatrix.postScale(mScale, mScale, mScreenCenter.x, mScreenCenter.y);

            executeTranslate();

            resetBase();
        }
    }

    private void initCenterCrop() {
        if (mImgRect.width() < mWidgetRect.width() || mImgRect.height() < mWidgetRect.height()) {
            float scaleX = mWidgetRect.width() / mImgRect.width();
            float scaleY = mWidgetRect.height() / mImgRect.height();

            mScale = scaleX > scaleY ? scaleX : scaleY;

            mAnimaMatrix.postScale(mScale, mScale, mScreenCenter.x, mScreenCenter.y);

            executeTranslate();
            resetBase();
        }
    }

    private void initCenterInside() {
        if (mImgRect.width() > mWidgetRect.width() || mImgRect.height() > mWidgetRect.height()) {
            float scaleX = mWidgetRect.width() / mImgRect.width();
            float scaleY = mWidgetRect.height() / mImgRect.height();

            mScale = scaleX < scaleY ? scaleX : scaleY;

            mAnimaMatrix.postScale(mScale, mScale, mScreenCenter.x, mScreenCenter.y);

            executeTranslate();
            resetBase();
        }
    }

    private void initFitCenter() {
        if (mImgRect.width() < mWidgetRect.width()) {
            mScale = mWidgetRect.width() / mImgRect.width();

            mAnimaMatrix.postScale(mScale, mScale, mScreenCenter.x, mScreenCenter.y);

            executeTranslate();
            resetBase();
        }
    }

    private void initFitStart() {
        initFitCenter();

        float ty = -mImgRect.top;
        mTranslateY += ty;
        mAnimaMatrix.postTranslate(0, ty);
        executeTranslate();
        resetBase();
    }

    private void initFitEnd() {
        initFitCenter();

        float ty = (mWidgetRect.bottom - mImgRect.bottom);
        mTranslateY += ty;
        mAnimaMatrix.postTranslate(0, ty);
        executeTranslate();
        resetBase();
    }

    private void initFitXY() {
        float scaleX = mWidgetRect.width() / mImgRect.width();
        float scaleY = mWidgetRect.height() / mImgRect.height();

        mAnimaMatrix.postScale(scaleX, scaleY, mScreenCenter.x, mScreenCenter.y);

        executeTranslate();
        resetBase();
    }

    private void resetBase() {
        Drawable img = getDrawable();
        int imgw = getDrawableWidth(img);
        int imgh = getDrawableHeight(img);
        mBaseRect.set(0, 0, imgw, imgh);
        mBaseMatrix.set(mSynthesisMatrix);
        mBaseMatrix.mapRect(mBaseRect);
        mHalfBaseRectWidth = mBaseRect.width() / 2;
        mHalfBaseRectHeight = mBaseRect.height() / 2;
        mScale = 1;
        mTranslateX = 0;
        mTranslateY = 0;
        mAnimaMatrix.reset();
    }

    private void executeTranslate() {
        mSynthesisMatrix.set(mBaseMatrix);
        mSynthesisMatrix.postConcat(mAnimaMatrix);
        setImageMatrix(mSynthesisMatrix);

        mAnimaMatrix.mapRect(mImgRect, mBaseRect);

        imgLargeWidth = mImgRect.width() > mWidgetRect.width();
        imgLargeHeight = mImgRect.height() > mWidgetRect.height();
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        if (!hasDrawable) {
            super.onMeasure(widthMeasureSpec, heightMeasureSpec);
            return;
        }

        Drawable d = getDrawable();
        int drawableW = getDrawableWidth(d);
        int drawableH = getDrawableHeight(d);

        int pWidth = MeasureSpec.getSize(widthMeasureSpec);
        int pHeight = MeasureSpec.getSize(heightMeasureSpec);

        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        int heightMode = MeasureSpec.getMode(heightMeasureSpec);

        int width = 0;
        int height = 0;

        ViewGroup.LayoutParams p = getLayoutParams();

        if (p == null) {
            p = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
        }

        if (p.width == ViewGroup.LayoutParams.MATCH_PARENT) {
            if (widthMode == MeasureSpec.UNSPECIFIED) {
                width = drawableW;
            } else {
                width = pWidth;
            }
        } else {
            if (widthMode == MeasureSpec.EXACTLY) {
                width = pWidth;
            } else if (widthMode == MeasureSpec.AT_MOST) {
                width = drawableW > pWidth ? pWidth : drawableW;
            } else {
                width = drawableW;
            }
        }

        if (p.height == ViewGroup.LayoutParams.MATCH_PARENT) {
            if (heightMode == MeasureSpec.UNSPECIFIED) {
                height = drawableH;
            } else {
                height = pHeight;
            }
        } else {
            if (heightMode == MeasureSpec.EXACTLY) {
                height = pHeight;
            } else if (heightMode == MeasureSpec.AT_MOST) {
                height = drawableH > pHeight ? pHeight : drawableH;
            } else {
                height = drawableH;
            }
        }

        if (mAdjustViewBounds && (float) drawableW / drawableH != (float) width / height) {

            float hScale = (float) height / drawableH;
            float wScale = (float) width / drawableW;

            float scale = hScale < wScale ? hScale : wScale;
            width = p.width == ViewGroup.LayoutParams.MATCH_PARENT ? width : (int) (drawableW * scale);
            height = p.height == ViewGroup.LayoutParams.MATCH_PARENT ? height : (int) (drawableH * scale);
        }

        setMeasuredDimension(width, height);
    }

    @Override
    public void setAdjustViewBounds(boolean adjustViewBounds) {
        super.setAdjustViewBounds(adjustViewBounds);
        mAdjustViewBounds = adjustViewBounds;
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);

        mWidgetRect.set(0, 0, w, h);
        mScreenCenter.set(w / 2, h / 2);

        if (!isKnowSize) {
            isKnowSize = true;
            initBase();
        }
    }

    @Override
    public void draw(Canvas canvas) {
        if (mClip != null) {
            canvas.clipRect(mClip);
            mClip = null;
        }
        super.draw(canvas);
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent event) {
        if (isEnable) {
            final int Action = event.getActionMasked();
            if (event.getPointerCount() >= 2) hasMultiTouch = true;

            mDetector.onTouchEvent(event);
            mRotateDetector.onTouchEvent(event);
            mScaleDetector.onTouchEvent(event);
            if (Action == MotionEvent.ACTION_UP || Action == MotionEvent.ACTION_CANCEL) onUp(event);

            return true;
        } else {
            return super.dispatchTouchEvent(event);
        }
    }

    private void onUp(MotionEvent ev) {
        if (mTranslate.isRuning) return;

        if (canRotate || mDegrees % 90 != 0) {
            float toDegrees = (int) (mDegrees / 90) * 90;
            float remainder = mDegrees % 90;

            if (remainder > 45)
                toDegrees += 90;
            else if (remainder < -45)
                toDegrees -= 90;

            mTranslate.withRotate((int) mDegrees, (int) toDegrees);

            mDegrees = toDegrees;
        }

        float scale = mScale;

        if (mScale < 1) {
            scale = 1;
            mTranslate.withScale(mScale, 1);
        } else if (mScale > MAX_SCALE) {
            scale = MAX_SCALE;
            mTranslate.withScale(mScale, MAX_SCALE);
        }

        float cx = mImgRect.left + mImgRect.width() / 2;
        float cy = mImgRect.top + mImgRect.height() / 2;

        mScaleCenter.set(cx, cy);
        mRotateCenter.set(cx, cy);
        mTranslateX = 0;
        mTranslateY = 0;

        mTmpMatrix.reset();
        mTmpMatrix.postTranslate(-mBaseRect.left, -mBaseRect.top);
        mTmpMatrix.postTranslate(cx - mHalfBaseRectWidth, cy - mHalfBaseRectHeight);
        mTmpMatrix.postScale(scale, scale, cx, cy);
        mTmpMatrix.postRotate(mDegrees, cx, cy);
        mTmpMatrix.mapRect(mTmpRect, mBaseRect);

        doTranslateReset(mTmpRect);
        mTranslate.start();
    }

    private void doTranslateReset(RectF imgRect) {
        int tx = 0;
        int ty = 0;

        if (imgRect.width() <= mWidgetRect.width()) {
            if (!isImageCenterWidth(imgRect))
                tx = -(int) ((mWidgetRect.width() - imgRect.width()) / 2 - imgRect.left);
        } else {
            if (imgRect.left > mWidgetRect.left) {
                tx = (int) (imgRect.left - mWidgetRect.left);
            } else if (imgRect.right < mWidgetRect.right) {
                tx = (int) (imgRect.right - mWidgetRect.right);
            }
        }

        if (imgRect.height() <= mWidgetRect.height()) {
            if (!isImageCenterHeight(imgRect))
                ty = -(int) ((mWidgetRect.height() - imgRect.height()) / 2 - imgRect.top);
        } else {
            if (imgRect.top > mWidgetRect.top) {
                ty = (int) (imgRect.top - mWidgetRect.top);
            } else if (imgRect.bottom < mWidgetRect.bottom) {
                ty = (int) (imgRect.bottom - mWidgetRect.bottom);
            }
        }

        if (tx != 0 || ty != 0) {
            if (!mTranslate.mFlingScroller.isFinished()) mTranslate.mFlingScroller.abortAnimation();
            mTranslate.withTranslate(mTranslateX, mTranslateY, -tx, -ty);
        }
    }

    private boolean isImageCenterHeight(RectF rect) {
        return Math.abs(Math.round(rect.top) - (mWidgetRect.height() - rect.height()) / 2) < 1;
    }

    private boolean isImageCenterWidth(RectF rect) {
        return Math.abs(Math.round(rect.left) - (mWidgetRect.width() - rect.width()) / 2) < 1;
    }

    private OnRotateListener mRotateListener = new OnRotateListener() {
        @Override
        public void onRotate(float degrees, float focusX, float focusY) {
            mRotateFlag += degrees;
            if (canRotate) {
                mDegrees += degrees;
                mAnimaMatrix.postRotate(degrees, focusX, focusY);
            } else {
                if (Math.abs(mRotateFlag) >= MIN_ROTATE) {
                    canRotate = true;
                    mRotateFlag = 0;
                }
            }
        }
    };

    private ScaleGestureDetector.OnScaleGestureListener mScaleListener = new ScaleGestureDetector.OnScaleGestureListener() {
        @Override
        public boolean onScale(ScaleGestureDetector detector) {
            float scaleFactor = detector.getScaleFactor();

            if (Float.isNaN(scaleFactor) || Float.isInfinite(scaleFactor))
                return false;

            mScale *= scaleFactor;
// mScaleCenter.set(detector.getFocusX(), detector.getFocusY());  mAnimaMatrix.postScale(scaleFactor, scaleFactor, detector.getFocusX(), detector.getFocusY());
            executeTranslate();
            return true;
        }

        public boolean onScaleBegin(ScaleGestureDetector detector) {
            return true;
        }

        public void onScaleEnd(ScaleGestureDetector detector) {

        }
    };

    private float resistanceScrollByX(float overScroll, float detalX) {
        float s = detalX * (Math.abs(Math.abs(overScroll) - MAX_OVER_RESISTANCE) / (float) MAX_OVER_RESISTANCE);
        return s;
    }

    private float resistanceScrollByY(float overScroll, float detalY) {
        float s = detalY * (Math.abs(Math.abs(overScroll) - MAX_OVER_RESISTANCE) / (float) MAX_OVER_RESISTANCE);
        return s;
    }

    /**  * 匹配两个Rect的共同部分输出到out，若无共同部分则输出0，0，0，0  */  private void mapRect(RectF r1, RectF r2, RectF out) {

        float l, r, t, b;

        l = r1.left > r2.left ? r1.left : r2.left;
        r = r1.right < r2.right ? r1.right : r2.right;

        if (l > r) {
            out.set(0, 0, 0, 0);
            return;
        }

        t = r1.top > r2.top ? r1.top : r2.top;
        b = r1.bottom < r2.bottom ? r1.bottom : r2.bottom;

        if (t > b) {
            out.set(0, 0, 0, 0);
            return;
        }

        out.set(l, t, r, b);
    }

    private void checkRect() {
        if (!hasOverTranslate) {
            mapRect(mWidgetRect, mImgRect, mCommonRect);
        }
    }

    private Runnable mClickRunnable = new Runnable() {
        @Override
        public void run() {
            if (mClickListener != null) {
                mClickListener.onClick(PhotoView.this);
            }
        }
    };

    private GestureDetector.OnGestureListener mGestureListener = new GestureDetector.SimpleOnGestureListener() {

        @Override
        public boolean onDown(MotionEvent e) {
            hasOverTranslate = false;
            hasMultiTouch = false;
            canRotate = false;
            removeCallbacks(mClickRunnable);
            return false;
        }

        @Override
        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
            if (hasMultiTouch) return false;
            if (!imgLargeWidth && !imgLargeHeight) return false;
            if (mTranslate.isRuning) return false;

            float vx = velocityX;
            float vy = velocityY;

            if (Math.round(mImgRect.left) >= mWidgetRect.left || Math.round(mImgRect.right) <= mWidgetRect.right) {
                vx = 0;
            }

            if (Math.round(mImgRect.top) >= mWidgetRect.top || Math.round(mImgRect.bottom) <= mWidgetRect.bottom) {
                vy = 0;
            }

            if (canRotate || mDegrees % 90 != 0) {
                float toDegrees = (int) (mDegrees / 90) * 90;
                float remainder = mDegrees % 90;

                if (remainder > 45)
                    toDegrees += 90;
                else if (remainder < -45)
                    toDegrees -= 90;

                mTranslate.withRotate((int) mDegrees, (int) toDegrees);

                mDegrees = toDegrees;

            }

            doTranslateReset(mImgRect);
            mTranslate.withFling(vx, vy);

            onUp(e2);
            mTranslate.start();
            return super.onFling(e1, e2, velocityX, velocityY);
        }

        @Override
        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
            if (mTranslate.isRuning) {
                mTranslate.stop();
            }

            if (canScrollHorizontallySelf(distanceX)) {
                if (distanceX < 0 && mImgRect.left - distanceX > mWidgetRect.left)
                    distanceX = mImgRect.left;
                if (distanceX > 0 && mImgRect.right - distanceX < mWidgetRect.right)
                    distanceX = mImgRect.right - mWidgetRect.right;

                mAnimaMatrix.postTranslate(-distanceX, 0);
                mTranslateX -= distanceX;
            } else if (imgLargeWidth || hasMultiTouch || hasOverTranslate) {
                checkRect();
                if (!hasMultiTouch) {
                    if (distanceX < 0 && mImgRect.left - distanceX > mCommonRect.left)
                        distanceX = resistanceScrollByX(mImgRect.left - mCommonRect.left, distanceX);
                    if (distanceX > 0 && mImgRect.right - distanceX < mCommonRect.right)
                        distanceX = resistanceScrollByX(mImgRect.right - mCommonRect.right, distanceX);
                }

                mTranslateX -= distanceX;
                mAnimaMatrix.postTranslate(-distanceX, 0);
                hasOverTranslate = true;
            }

            if (canScrollVerticallySelf(distanceY)) {
                if (distanceY < 0 && mImgRect.top - distanceY > mWidgetRect.top)
                    distanceY = mImgRect.top;
                if (distanceY > 0 && mImgRect.bottom - distanceY < mWidgetRect.bottom)
                    distanceY = mImgRect.bottom - mWidgetRect.bottom;

                mAnimaMatrix.postTranslate(0, -distanceY);
                mTranslateY -= distanceY;
            } else if (imgLargeHeight || hasOverTranslate || hasMultiTouch) {
                checkRect();
                if (!hasMultiTouch) {
                    if (distanceY < 0 && mImgRect.top - distanceY > mCommonRect.top)
                        distanceY = resistanceScrollByY(mImgRect.top - mCommonRect.top, distanceY);
                    if (distanceY > 0 && mImgRect.bottom - distanceY < mCommonRect.bottom)
                        distanceY = resistanceScrollByY(mImgRect.bottom - mCommonRect.bottom, distanceY);
                }

                mAnimaMatrix.postTranslate(0, -distanceY);
                mTranslateY -= distanceY;
                hasOverTranslate = true;
            }

            executeTranslate();
            return true;
        }

        @Override
        public boolean onSingleTapUp(MotionEvent e) {
            postDelayed(mClickRunnable, 250);
            return false;
        }

        @Override
        public boolean onDoubleTap(MotionEvent e) {

            mTranslate.stop();

            float from = 1;
            float to = 1;

            float imgcx = mImgRect.left + mImgRect.width() / 2;
            float imgcy = mImgRect.top + mImgRect.height() / 2;

            mScaleCenter.set(imgcx, imgcy);
            mRotateCenter.set(imgcx, imgcy);
            mTranslateX = 0;
            mTranslateY = 0;

            if (isZoonUp) {
                from = mScale;
                to = 1;
            } else {
                from = mScale;
                to = MAX_SCALE;

                mScaleCenter.set(e.getX(), e.getY());
            }

            mTmpMatrix.reset();
            mTmpMatrix.postTranslate(-mBaseRect.left, -mBaseRect.top);
            mTmpMatrix.postTranslate(mRotateCenter.x, mRotateCenter.y);
            mTmpMatrix.postTranslate(-mHalfBaseRectWidth, -mHalfBaseRectHeight);
            mTmpMatrix.postRotate(mDegrees, mRotateCenter.x, mRotateCenter.y);
            mTmpMatrix.postScale(to, to, mScaleCenter.x, mScaleCenter.y);
            mTmpMatrix.postTranslate(mTranslateX, mTranslateY);
            mTmpMatrix.mapRect(mTmpRect, mBaseRect);
            doTranslateReset(mTmpRect);

            isZoonUp = !isZoonUp;
            mTranslate.withScale(from, to);
            mTranslate.start();

            return false;
        }
    };

    public boolean canScrollHorizontallySelf(float direction) {
        if (mImgRect.width() <= mWidgetRect.width()) return false;
        if (direction < 0 && Math.round(mImgRect.left) - direction >= mWidgetRect.left)
            return false;
        if (direction > 0 && Math.round(mImgRect.right) - direction <= mWidgetRect.right)
            return false;
        return true;
    }

    public boolean canScrollVerticallySelf(float direction) {
        if (mImgRect.height() <= mWidgetRect.height()) return false;
        if (direction < 0 && Math.round(mImgRect.top) - direction >= mWidgetRect.top)
            return false;
        if (direction > 0 && Math.round(mImgRect.bottom) - direction <= mWidgetRect.bottom)
            return false;
        return true;
    }

    @Override
    public boolean canScrollHorizontally(int direction) {
        if (hasMultiTouch) return true;
        return canScrollHorizontallySelf(direction);
    }

    @Override
    public boolean canScrollVertically(int direction) {
        if (hasMultiTouch) return true;
        return canScrollVerticallySelf(direction);
    }

    private class Transform implements Runnable {

        boolean isRuning;

        OverScroller mTranslateScroller;
        OverScroller mFlingScroller;
        Scroller mScaleScroller;
        Scroller mClipScroller;
        Scroller mRotateScroller;

        ClipCalculate C;

        int mLastFlingX;
        int mLastFlingY;

        int mLastTranslateX;
        int mLastTranslateY;

        RectF mClipRect = new RectF();

        Transform() {
            Context ctx = getContext();
            DecelerateInterpolator i = new DecelerateInterpolator();
            mTranslateScroller = new OverScroller(ctx, i);
            mScaleScroller = new Scroller(ctx, i);
            mFlingScroller = new OverScroller(ctx, i);
            mClipScroller = new Scroller(ctx, i);
            mRotateScroller = new Scroller(ctx, i);
        }

        void withTranslate(int startX, int startY, int deltaX, int deltaY) {
            mLastTranslateX = 0;
            mLastTranslateY = 0;
            mTranslateScroller.startScroll(0, 0, deltaX, deltaY, ANIMA_DURING);
        }

        void withScale(float form, float to) {
            mScaleScroller.startScroll((int) (form * 10000), 0, (int) ((to - form) * 10000), 0, ANIMA_DURING);
        }

        void withClip(float fromX, float fromY, float deltaX, float deltaY, int d, ClipCalculate c) {
            mClipScroller.startScroll((int) (fromX * 10000), (int) (fromY * 10000), (int) (deltaX * 10000), (int) (deltaY * 10000), d);
            C = c;
        }

        void withRotate(int fromDegrees, int toDegrees) {
            mRotateScroller.startScroll(fromDegrees, 0, toDegrees - fromDegrees, 0, ANIMA_DURING);
        }

        void withRotate(int fromDegrees, int toDegrees, int during) {
            mRotateScroller.startScroll(fromDegrees, 0, toDegrees - fromDegrees, 0, during);
        }

        void withFling(float velocityX, float velocityY) {
            mLastFlingX = velocityX < 0 ? Integer.MAX_VALUE : 0;
            int distanceX = (int) (velocityX > 0 ? Math.abs(mImgRect.left) : mImgRect.right - mWidgetRect.right);
            distanceX = velocityX < 0 ? Integer.MAX_VALUE - distanceX : distanceX;
            int minX = velocityX < 0 ? distanceX : 0;
            int maxX = velocityX < 0 ? Integer.MAX_VALUE : distanceX;
            int overX = velocityX < 0 ? Integer.MAX_VALUE - minX : distanceX;

            mLastFlingY = velocityY < 0 ? Integer.MAX_VALUE : 0;
            int distanceY = (int) (velocityY > 0 ? Math.abs(mImgRect.top) : mImgRect.bottom - mWidgetRect.bottom);
            distanceY = velocityY < 0 ? Integer.MAX_VALUE - distanceY : distanceY;
            int minY = velocityY < 0 ? distanceY : 0;
            int maxY = velocityY < 0 ? Integer.MAX_VALUE : distanceY;
            int overY = velocityY < 0 ? Integer.MAX_VALUE - minY : distanceY;

            if (velocityX == 0) {
                maxX = 0;
                minX = 0;
            }

            if (velocityY == 0) {
                maxY = 0;
                minY = 0;
            }

            mFlingScroller.fling(mLastFlingX, mLastFlingY, (int) velocityX, (int) velocityY, minX, maxX, minY, maxY, Math.abs(overX) < MAX_FLING_OVER_SCROLL * 2 ? 0 : MAX_FLING_OVER_SCROLL, Math.abs(overY) < MAX_FLING_OVER_SCROLL * 2 ? 0 : MAX_FLING_OVER_SCROLL);
        }

        void start() {
            isRuning = true;
            postExecute();
        }

        void stop() {
            removeCallbacks(this);
            mTranslateScroller.abortAnimation();
            mScaleScroller.abortAnimation();
            mFlingScroller.abortAnimation();
            mRotateScroller.abortAnimation();
            isRuning = false;
        }

        @Override
        public void run() {

            if (!isRuning) return;

            boolean endAnima = true;

            if (mScaleScroller.computeScrollOffset()) {
                mScale = mScaleScroller.getCurrX() / 10000f;
                endAnima = false;
            }

            if (mTranslateScroller.computeScrollOffset()) {
                int tx = mTranslateScroller.getCurrX() - mLastTranslateX;
                int ty = mTranslateScroller.getCurrY() - mLastTranslateY;
                mTranslateX += tx;
                mTranslateY += ty;
                mLastTranslateX = mTranslateScroller.getCurrX();
                mLastTranslateY = mTranslateScroller.getCurrY();
                endAnima = false;
            }

            if (mFlingScroller.computeScrollOffset()) {
                int x = mFlingScroller.getCurrX() - mLastFlingX;
                int y = mFlingScroller.getCurrY() - mLastFlingY;

                mLastFlingX = mFlingScroller.getCurrX();
                mLastFlingY = mFlingScroller.getCurrY();

                mTranslateX += x;
                mTranslateY += y;
                endAnima = false;
            }

            if (mRotateScroller.computeScrollOffset()) {
                mDegrees = mRotateScroller.getCurrX();
                endAnima = false;
            }

            if (mClipScroller.computeScrollOffset() || mClip != null) {
                float sx = mClipScroller.getCurrX() / 10000f;
                float sy = mClipScroller.getCurrY() / 10000f;
                mTmpMatrix.setScale(sx, sy, (mImgRect.left + mImgRect.right) / 2, C.calculateTop());
                mTmpMatrix.mapRect(mClipRect, mImgRect);

                if (sx == 1) {
                    mClipRect.left = mWidgetRect.left;
                    mClipRect.right = mWidgetRect.right;
                }

                if (sy == 1) {
                    mClipRect.top = mWidgetRect.top;
                    mClipRect.bottom = mWidgetRect.bottom;
                }

                mClip = mClipRect;
            }

            if (!endAnima) {
                mAnimaMatrix.reset();
                mAnimaMatrix.postTranslate(-mBaseRect.left, -mBaseRect.top);
                mAnimaMatrix.postTranslate(mRotateCenter.x, mRotateCenter.y);
                mAnimaMatrix.postTranslate(-mHalfBaseRectWidth, -mHalfBaseRectHeight);
                mAnimaMatrix.postRotate(mDegrees, mRotateCenter.x, mRotateCenter.y);
                mAnimaMatrix.postScale(mScale, mScale, mScaleCenter.x, mScaleCenter.y);
                mAnimaMatrix.postTranslate(mTranslateX, mTranslateY);
                executeTranslate();
                postExecute();
            } else {
                isRuning = false;
                invalidate();

                if (mCompleteCallBack != null) {
                    mCompleteCallBack.run();
                    mCompleteCallBack = null;
                }
            }
        }

        private void postExecute() {
            if (isRuning) post(this);
        }
    }

    public Info getInfo() {
        RectF rect = new RectF();
        RectF local = new RectF();
        int[] p = new int[2];
        getLocation(p);
        rect.set(p[0] + mImgRect.left, p[1] + mImgRect.top, p[0] + mImgRect.right, p[1] + mImgRect.bottom);
        local.set(p[0], p[1], p[0] + mImgRect.width(), p[1] + mImgRect.height());
        return new Info(rect, local, mImgRect, mWidgetRect, mScale, mDegrees, mScaleType);
    }

    private void getLocation(int[] position) {

        position[0] += getLeft();
        position[1] += getTop();

        ViewParent viewParent = getParent();
        while (viewParent instanceof View) {
            final View view = (View) viewParent;

            if (view.getId() == android.R.id.content) return;

            position[0] -= view.getScrollX();
            position[1] -= view.getScrollY();

            position[0] += view.getLeft();
            position[1] += view.getTop();

            viewParent = view.getParent();
        }

        position[0] = (int) (position[0] + 0.5f);
        position[1] = (int) (position[1] + 0.5f);
    }

    private void reset() {
        mAnimaMatrix.reset();
        executeTranslate();
        mScale = 1;
        mTranslateX = 0;
        mTranslateY = 0;
    }

    public interface ClipCalculate {
        float calculateTop();
    }

    public class START implements ClipCalculate {
        public float calculateTop() {
            return mImgRect.top;
        }
    }

    public class END implements ClipCalculate {
        public float calculateTop() {
            return mImgRect.bottom;
        }
    }

    public class OTHER implements ClipCalculate {
        public float calculateTop() {
            return (mImgRect.top + mImgRect.bottom) / 2;
        }
    }

    /**  * 在PhotoView内部还没有图片的时候同样可以调用该方法  * <p></p>  * 此时并不会播放动画，当给PhotoView设置图片后会自动播放动画。  * <p></p>  * 若等待时间过长也没有给控件设置图片，则会忽略该动画，若要再次播放动画则需要重新调用该方法  * (等待的时间默认500毫秒，可以通过setMaxAnimFromWaiteTime(int)设置最大等待时间)  */  public void animaFrom(Info info) {

        if (isInit) {
            reset();

            Info mine = getInfo();

            float scaleX = info.mImgRect.width() / mine.mImgRect.width();
            float scaleY = info.mImgRect.height() / mine.mImgRect.height();
            float scale = scaleX < scaleY ? scaleX : scaleY;

            float ocx = info.mRect.left + info.mRect.width() / 2;
            float ocy = info.mRect.top + info.mRect.height() / 2;

            mAnimaMatrix.reset();
            mAnimaMatrix.postTranslate(-mBaseRect.left, -mBaseRect.top);
            mAnimaMatrix.postTranslate(ocx - mBaseRect.width() / 2, ocy - mBaseRect.height() / 2);
            mAnimaMatrix.postScale(scale, scale, ocx, ocy);
            mAnimaMatrix.postRotate(info.mDegrees, ocx, ocy);
            executeTranslate();

            mScaleCenter.set(ocx, ocy);
            mRotateCenter.set(ocx, ocy);

            mTranslate.withTranslate(0, 0, (int) (mScreenCenter.x - ocx), (int) (mScreenCenter.y - ocy));
            mTranslate.withScale(scale, 1);
            mTranslate.withRotate((int) info.mDegrees, 0);

            if (info.mWidgetRect.width() < info.mImgRect.width() || info.mWidgetRect.height() < info.mImgRect.height()) {
                float clipX = info.mWidgetRect.width() / info.mImgRect.width();
                float clipY = info.mWidgetRect.height() / info.mImgRect.height();
                clipX = clipX > 1 ? 1 : clipX;
                clipY = clipY > 1 ? 1 : clipY;

                ClipCalculate c = info.mScaleType == ScaleType.FIT_START ? new START() : info.mScaleType == ScaleType.FIT_END ? new END() : new OTHER();

                mTranslate.withClip(clipX, clipY, 1 - clipX, 1 - clipY, ANIMA_DURING / 3, c);

                mTmpMatrix.setScale(clipX, clipY, (mImgRect.left + mImgRect.right) / 2, c.calculateTop());
                mTmpMatrix.mapRect(mTranslate.mClipRect, mImgRect);
                mClip = mTranslate.mClipRect;
            }

            mTranslate.start();
        } else {
            mInfo = info;
            mInfoTime = System.currentTimeMillis();
        }
    }

    public void animaTo(Info info, Runnable completeCallBack) {
        if (isInit) {
            mTranslate.stop();

            mTranslateX = 0;
            mTranslateY = 0;

            float tcx = info.mRect.left + info.mRect.width() / 2;
            float tcy = info.mRect.top + info.mRect.height() / 2;

            mScaleCenter.set(mImgRect.left + mImgRect.width() / 2, mImgRect.top + mImgRect.height() / 2);
            mRotateCenter.set(mScaleCenter);

            // 将图片旋转回正常位置，用以计算  mAnimaMatrix.postRotate(-mDegrees, mScaleCenter.x, mScaleCenter.y);
            mAnimaMatrix.mapRect(mImgRect, mBaseRect);

            // 缩放  float scaleX = info.mImgRect.width() / mBaseRect.width();
            float scaleY = info.mImgRect.height() / mBaseRect.height();
            float scale = scaleX > scaleY ? scaleX : scaleY;

            mAnimaMatrix.postRotate(mDegrees, mScaleCenter.x, mScaleCenter.y);
            mAnimaMatrix.mapRect(mImgRect, mBaseRect);

            mDegrees = mDegrees % 360;

            mTranslate.withTranslate(0, 0, (int) (tcx - mScaleCenter.x), (int) (tcy - mScaleCenter.y));
            mTranslate.withScale(mScale, scale);
            mTranslate.withRotate((int) mDegrees, (int) info.mDegrees, ANIMA_DURING * 2 / 3);

            if (info.mWidgetRect.width() < info.mRect.width() || info.mWidgetRect.height() < info.mRect.height()) {
                float clipX = info.mWidgetRect.width() / info.mRect.width();
                float clipY = info.mWidgetRect.height() / info.mRect.height();
                clipX = clipX > 1 ? 1 : clipX;
                clipY = clipY > 1 ? 1 : clipY;

                final float cx = clipX;
                final float cy = clipY;
                final ClipCalculate c = info.mScaleType == ScaleType.FIT_START ? new START() : info.mScaleType == ScaleType.FIT_END ? new END() : new OTHER();

                postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        mTranslate.withClip(1, 1, -1 + cx, -1 + cy, ANIMA_DURING / 2, c);
                    }
                }, ANIMA_DURING / 2);
            }

            mCompleteCallBack = completeCallBack;
            mTranslate.start();
        }
    }
}
Info类代码如下：

package cn.doolii.shopping.view;

import android.graphics.RectF;
import android.widget.ImageView;

/**  * Created by liuheng on 2015/8/19.  */ public class Info {
    // 内部图片在整个窗口的位置  RectF mRect = new RectF();
    // 控件在窗口的位置  RectF mLocalRect = new RectF();
    RectF mImgRect = new RectF();
    RectF mWidgetRect = new RectF();
    float mScale;
    float mDegrees;
    ImageView.ScaleType mScaleType;

    public Info(RectF rect, RectF local, RectF img, RectF widget, float scale, float degrees, ImageView.ScaleType scaleType) {
        mRect.set(rect);
        mLocalRect.set(local);
        mImgRect.set(img);
        mWidgetRect.set(widget);
        mScale = scale;
        mScaleType = scaleType;
        mDegrees = degrees;
    }
}
自定义的viewpager动画
RotateDownPageTransformer 
代码如下：

package cn.doolii.shopping.view;

import android.support.v4.view.ViewPager.PageTransformer;
import android.util.Log;
import android.view.View;

public class RotateDownPageTransformer implements PageTransformer
{  
      
    private static final float ROT_MAX = 20.0f;  
    private float mRot;  
      
  
      
    public void transformPage(View view, float position)
    {  
  
        Log.e("TAG", view + " , " + position + "");
  
        if (position < -1)  
        { // [-Infinity,-1)  // This page is way off-screen to the left.  view.setRotation( 0);
  
        } else if (position <= 1) // a页滑动至b页 ； a页从 0.0 ~ -1 ；b页从1 ~ 0.0  { // [-1,1]  // Modify the default slide transition to shrink the page as well  if (position < 0)  
            {  
  
                mRot = (ROT_MAX * position);
                view.setPivotX( view.getMeasuredWidth() * 0.5f);
                view.setPivotY( view.getMeasuredHeight());
                view.setRotation( mRot);
            } else  {  
  
                mRot = (ROT_MAX * position);
                view.setPivotX( view.getMeasuredWidth() * 0.5f);
                view.setPivotY(view.getMeasuredHeight());
                view.setRotation( mRot);
            }  
  
            // Scale the page down (between MIN_SCALE and 1)   // Fade the page relative to its size.   } else  { // (1,+Infinity]  // This page is way off-screen to the right.  view.setRotation( 0);
        }  
    }  
}  
RotateGestureDetector 旋转手势类代码如下

package cn.doolii.shopping.view;

import android.view.MotionEvent;

/**  * Created by q2366 on 2015/10/12.  */ public class RotateGestureDetector {

    private static final int MAX_DEGREES_STEP = 120;

    private OnRotateListener mListener;

    private float mPrevSlope;
    private float mCurrSlope;

    private float x1;
    private float y1;
    private float x2;
    private float y2;

    public RotateGestureDetector(OnRotateListener l) {
        mListener = l;
    }

    public void onTouchEvent(MotionEvent event) {

        final int Action = event.getActionMasked();

        switch (Action) {
            case MotionEvent.ACTION_POINTER_DOWN:
            case MotionEvent.ACTION_POINTER_UP:
                if (event.getPointerCount() == 2) mPrevSlope = caculateSlope(event);
                break;
            case MotionEvent.ACTION_MOVE:
                if (event.getPointerCount() > 1) {
                    mCurrSlope = caculateSlope(event);

                    double currDegrees = Math.toDegrees(Math.atan(mCurrSlope));
                    double prevDegrees = Math.toDegrees(Math.atan(mPrevSlope));

                    double deltaSlope = currDegrees - prevDegrees;

                    if (Math.abs(deltaSlope) <= MAX_DEGREES_STEP) {
                        if (mListener != null)
                            mListener.onRotate((float) deltaSlope, (x2 + x1) / 2, (y2 + y1) / 2);
                    }
                    mPrevSlope = mCurrSlope;
                }
                break;
            default:
                break;
        }
    }

    private float caculateSlope(MotionEvent event) {
        x1 = event.getX(0);
        y1 = event.getY(0);
        x2 = event.getX(1);
        y2 = event.getY(1);
        return (y2 - y1) / (x2 - x1);
    }
}

interface OnRotateListener {
    void onRotate(float degrees, float focusX, float focusY);
}

RotateGestureDetector 类代码如下：

package cn.doolii.shopping.view;

import android.view.MotionEvent;

/**  * Created by q2366 on 2015/10/12.  */ public class RotateGestureDetector {

    private static final int MAX_DEGREES_STEP = 120;

    private OnRotateListener mListener;

    private float mPrevSlope;
    private float mCurrSlope;

    private float x1;
    private float y1;
    private float x2;
    private float y2;

    public RotateGestureDetector(OnRotateListener l) {
        mListener = l;
    }

    public void onTouchEvent(MotionEvent event) {

        final int Action = event.getActionMasked();

        switch (Action) {
            case MotionEvent.ACTION_POINTER_DOWN:
            case MotionEvent.ACTION_POINTER_UP:
                if (event.getPointerCount() == 2) mPrevSlope = caculateSlope(event);
                break;
            case MotionEvent.ACTION_MOVE:
                if (event.getPointerCount() > 1) {
                    mCurrSlope = caculateSlope(event);

                    double currDegrees = Math.toDegrees(Math.atan(mCurrSlope));
                    double prevDegrees = Math.toDegrees(Math.atan(mPrevSlope));

                    double deltaSlope = currDegrees - prevDegrees;

                    if (Math.abs(deltaSlope) <= MAX_DEGREES_STEP) {
                        if (mListener != null)
                            mListener.onRotate((float) deltaSlope, (x2 + x1) / 2, (y2 + y1) / 2);
                    }
                    mPrevSlope = mCurrSlope;
                }
                break;
            default:
                break;
        }
    }

    private float caculateSlope(MotionEvent event) {
        x1 = event.getX(0);
        y1 = event.getY(0);
        x2 = event.getX(1);
        y2 = event.getY(1);
        return (y2 - y1) / (x2 - x1);
    }
}

interface OnRotateListener {
    void onRotate(float degrees, float focusX, float focusY);
}