Android 滑动效果进阶篇（六）—— 倒影效果

http://blog.csdn.net/sunboy_2050/article/details/7483169

上篇介绍了使用Animation实现3D动画旋转翻页效果，现在介绍图片倒影实现，先看效果图

本示例主要通过自定义Gallery和ImageAdapter（继承自BaseAdapter）实现

1、倒影绘制

ImageAdapter继承自BaseAdapter，详细实现可见 Android 滑动效果入门篇（二）—— Gallery 这里重点介绍倒影原理及实现

倒影原理：

倒影效果是主要由原图+间距+倒影三部分组成，高度大约为原图的3/2（原图为1、倒影为1/2）

原图，就是我们看到了最开始的图片

间距，是原图与倒影之间的间隙，如：reflectionGap = 4;

倒影，是原图下半部分1/2高度，通过矩阵变换matrix.preScale(1, -1); 获取倒立图片，然后再加上线性遮罩和阴影实现

倒影实现：

 /** 反射倒影 */
 public boolean createReflectedImages() {
     final int reflectionGap = 4;
     int index = 0;
     for (Map<String, Object> map : list) {
         Integer id = (Integer) map.get("image");
         Bitmap originalImage = BitmapFactory.decodeResource(mContext.getResources(), id);   // 获取原始图片
         int width = originalImage.getWidth();
         int height = originalImage.getHeight();

         Matrix matrix = new Matrix();
         matrix.preScale(1, -1);         // 图片矩阵变换（从低部向顶部的倒影）
         Bitmap reflectionImage = Bitmap.createBitmap(originalImage, 0, height/2, width, height/2, matrix, false);   // 截取原图下半部分
         Bitmap bitmapWithReflection = Bitmap.createBitmap(width, (height + height / 2), Config.ARGB_8888);          // 创建倒影图片（高度为原图3/2）

         Canvas canvas = new Canvas(bitmapWithReflection);   // 绘制倒影图（原图 + 间距 + 倒影）
         canvas.drawBitmap(originalImage, 0, 0, null);       // 绘制原图
         Paint paint = new Paint();
         canvas.drawRect(0, height, width, height + reflectionGap, paint);       // 绘制原图与倒影的间距
         canvas.drawBitmap(reflectionImage, 0, height + reflectionGap, null);    // 绘制倒影图

         paint = new Paint();
         LinearGradient shader = new LinearGradient(0, originalImage.getHeight(), 0, bitmapWithReflection.getHeight() + reflectionGap, 0x70ffffff, 0x00ffffff, TileMode.CLAMP);
         paint.setShader(shader);    // 线性渐变效果
         paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));     // 倒影遮罩效果
         canvas.drawRect(0, height, width, bitmapWithReflection.getHeight() + reflectionGap, paint);     // 绘制倒影的阴影效果

         ImageView imageView = new ImageView(mContext);
         imageView.setImageBitmap(bitmapWithReflection);     // 设置倒影图片
         imageView.setLayoutParams(new myGallery.LayoutParams(180, 240));
         imageView.setScaleType(ScaleType.MATRIX);
         mImages[index++] = imageView;
     }
     return true;
 }

2、myGallery

自定义Gallery来实现倒影图片的浏览与选择

 public class myGallery extends Gallery {

     private Camera mCamera = new Camera();
     private int mMaxRotationAngle = 60;     // 最大旋转角度 60
     private int mMaxZoom = -120;
     private int mCoveflowCenter;

     public myGallery(Context context) {
         super(context);
         this.setStaticTransformationsEnabled(true);
     }

     public myGallery(Context context, AttributeSet attrs) {
         super(context, attrs);
         this.setStaticTransformationsEnabled(true);
     }

     public myGallery(Context context, AttributeSet attrs, int defStyle) {
         super(context, attrs, defStyle);
         this.setStaticTransformationsEnabled(true);
     }

     public int getMaxRotationAngle() {
         return mMaxRotationAngle;
     }

     public void setMaxRotationAngle(int maxRotationAngle) {
         mMaxRotationAngle = maxRotationAngle;
     }

     public int getMaxZoom() {
         return mMaxZoom;
     }

     public void setMaxZoom(int maxZoom) {
         mMaxZoom = maxZoom;
     }

     /** 获取Gallery的中心x */
     private int getCenterOfCoverflow() {
         return (getWidth() - getPaddingLeft() - getPaddingRight()) / 2 + getPaddingLeft();
     }

     /** 获取View的中心x */
     private static int getCenterOfView(View view) {
         return view.getLeft() + view.getWidth() / 2;
     }

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

     @Override
     protected boolean getChildStaticTransformation(View child, Transformation trans) {
         final int childCenter = getCenterOfView(child);
         final int childWidth = child.getWidth();
         int rotationAngle = 0;

         trans.clear();
         trans.setTransformationType(Transformation.TYPE_BOTH);      // alpha 和 matrix 都变换

         if (childCenter == mCoveflowCenter) {   // 正中间的childView
             transformImageBitmap((ImageView) child, trans, 0);
         } else {        // 两侧的childView
             rotationAngle = (int) ( ( (float) (mCoveflowCenter - childCenter) / childWidth ) * mMaxRotationAngle );
             if (Math.abs(rotationAngle) > mMaxRotationAngle) {
                 rotationAngle = (rotationAngle < 0) ? -mMaxRotationAngle : mMaxRotationAngle;
             }
             transformImageBitmap((ImageView) child, trans, rotationAngle);
         }

         return true;
     }

     private void transformImageBitmap(ImageView child, Transformation trans, int rotationAngle) {
         mCamera.save();

         final Matrix imageMatrix = trans.getMatrix();
         final int imageHeight = child.getLayoutParams().height;
         final int imageWidth = child.getLayoutParams().width;
         final int rotation = Math.abs(rotationAngle);

         // 在Z轴上正向移动camera的视角，实际效果为放大图片; 如果在Y轴上移动，则图片上下移动; X轴上对应图片左右移动。
         mCamera.translate(0.0f, 0.0f, 100.0f);

         // As the angle of the view gets less, zoom in
         if (rotation < mMaxRotationAngle) {
             float zoomAmount = (float) (mMaxZoom + (rotation * 1.5));
             mCamera.translate(0.0f, 0.0f, zoomAmount);
         }

         mCamera.rotateY(rotationAngle);     // rotationAngle 为正，沿y轴向内旋转； 为负，沿y轴向外旋转

         mCamera.getMatrix(imageMatrix);
         imageMatrix.preTranslate(-(imageWidth / 2), -(imageHeight / 2));
         imageMatrix.postTranslate((imageWidth / 2), (imageHeight / 2));

         mCamera.restore();
     }
 }

3、Activity

Activity中，主要实现自定义Gallery的图片填充ImageAdapter、myGallery选择事件监听、点击事件监听

 private void initRes(){
     tvTitle = (TextView) findViewById(R.id.tvTitle);
     gallery = (myGallery) findViewById(R.id.mygallery);     // 获取自定义的myGallery控件

     adapter = new ImageAdapter(this);
     adapter.createReflectedImages();    // 创建倒影效果
     gallery.setAdapter(adapter);

     gallery.setOnItemSelectedListener(new OnItemSelectedListener() {    // 设置选择事件监听
         @Override
         public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
             tvTitle.setText(adapter.titles[position]);
         }

         @Override
         public void onNothingSelected(AdapterView<?> parent) {
         }
     });

     gallery.setOnItemClickListener(new OnItemClickListener() {          // 设置点击事件监听
         @Override
         public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
             Toast.makeText(Main.this, "img " + (position+1) + " selected", Toast.LENGTH_SHORT).show();
         }
     });
 }

main.xml布局文件中，通过实现自定义的myGallery，来显示图片集合

 <?xml version="1.0" encoding="utf-8"?>
 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="fill_parent"
     android:layout_height="fill_parent"
     android:orientation="vertical" >
     <TextView
         android:id="@+id/tvTitle"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_centerHorizontal="true"
         android:textSize="16sp" />

     <com.homer.reflect.myGallery
         android:id="@+id/mygallery"
         android:layout_width="fill_parent"
         android:layout_height="wrap_content"
         android:layout_below="@id/tvTitle"
         android:layout_marginTop="10dip" />
 </RelativeLayout>

源码下载

参考推荐：

Android实现图片的倒影效果

Android中图片倒影、圆角效果重绘