Android 自定义实现switch开关按钮

前几天在看蘑菇街上有个开关按钮：

就在想是怎样实现的，于是反编译了它的源码，但是这时得到了下面的几张图片：

图片对应的名称：

无色长条:switch_frame;

白色圆点:switch_btn_pressed;
左白右红的长条:switch_bottom;
黑色长条:switch_mask.

那我们就用这几张图片来实现类似的效果吧。

代码：

SwitchButton类：

 package com.example.switchbutton;

 import android.content.Context;
 import android.graphics.Bitmap;
 import android.graphics.BitmapFactory;
 import android.graphics.Canvas;
 import android.graphics.Paint;
 import android.graphics.PorterDuff.Mode;
 import android.graphics.PorterDuffXfermode;
 import android.graphics.Rect;
 import android.graphics.RectF;
 import android.util.AttributeSet;
 import android.view.MotionEvent;
 import android.view.View;

 public class SwitchButton extends View implements android.view.View.OnClickListener{
     private Bitmap mSwitchBottom, mSwitchThumb, mSwitchFrame, mSwitchMask;
     private float mCurrentX = 0;
     private boolean mSwitchOn = true;//开关默认是开着的
     private int mMoveLength;//最大移动距离
     private float mLastX = 0;//第一次按下的有效区域

     private Rect mDest = null;//绘制的目标区域大小
     private Rect mSrc = null;//截取源图片的大小
     private int mDeltX = 0;//移动的偏移量
     private Paint mPaint = null;
     private OnChangeListener mListener = null;
     private boolean mFlag = false;

     public SwitchButton(Context context) {
         this(context, null);
         // TODO Auto-generated constructor stub
     }

     public SwitchButton(Context context, AttributeSet attrs) {
         this(context, attrs, 0);
         // TODO Auto-generated constructor stub
     }

     public SwitchButton(Context context, AttributeSet attrs, int defStyle) {
         super(context, attrs, defStyle);
         // TODO Auto-generated constructor stub
         init();
     }

     /**
      * 初始化相关资源
      */
     public void init() {
         mSwitchBottom = BitmapFactory.decodeResource(getResources(),
                 R.drawable.switch_bottom);
         mSwitchThumb = BitmapFactory.decodeResource(getResources(),
                 R.drawable.switch_btn_pressed);
         mSwitchFrame = BitmapFactory.decodeResource(getResources(),
                 R.drawable.switch_frame);
         mSwitchMask = BitmapFactory.decodeResource(getResources(),
                 R.drawable.switch_mask);
         setOnClickListener(this);
         setOnTouchListener(new OnTouchListener() {

             @Override
             public boolean onTouch(View v, MotionEvent event) {
                 // TODO Auto-generated method stub
                 return false;
             }
         });

         mMoveLength = mSwitchBottom.getWidth() - mSwitchFrame.getWidth();
         mDest = new Rect(0, 0, mSwitchFrame.getWidth(), mSwitchFrame.getHeight());
         mSrc = new Rect();
         mPaint = new Paint();
         mPaint.setAntiAlias(true);
         mPaint.setAlpha(255);
         mPaint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));
     }

     @Override
     protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
         // TODO Auto-generated method stub
         setMeasuredDimension(mSwitchFrame.getWidth(), mSwitchFrame.getHeight());
     }

     @Override
     protected void onDraw(Canvas canvas) {
         // TODO Auto-generated method stub
         super.onDraw(canvas);
         if (mDeltX > 0 || mDeltX == 0 && mSwitchOn) {
             if(mSrc != null) {
                 mSrc.set(mMoveLength - mDeltX, 0, mSwitchBottom.getWidth()
                     - mDeltX, mSwitchFrame.getHeight());
             }
         } else if(mDeltX < 0 || mDeltX == 0 && !mSwitchOn){
             if(mSrc != null) {
                 mSrc.set(-mDeltX, 0, mSwitchFrame.getWidth() - mDeltX,
                     mSwitchFrame.getHeight());
             }
         }

 <span style="white-space:pre">        </span>//这儿是离屏缓冲，自己感觉类似双缓冲机制吧
         int count = canvas.saveLayer(new RectF(mDest), null, Canvas.MATRIX_SAVE_FLAG
                 | Canvas.CLIP_SAVE_FLAG | Canvas.HAS_ALPHA_LAYER_SAVE_FLAG
                 | Canvas.FULL_COLOR_LAYER_SAVE_FLAG
                 | Canvas.CLIP_TO_LAYER_SAVE_FLAG);

         canvas.drawBitmap(mSwitchBottom, mSrc, mDest, null);
         canvas.drawBitmap(mSwitchThumb, mSrc, mDest, null);
         canvas.drawBitmap(mSwitchFrame, 0, 0, null);
         canvas.drawBitmap(mSwitchMask, 0, 0, mPaint);
         canvas.restoreToCount(count);
     }

     @Override
     public boolean onTouchEvent(MotionEvent event) {
         // TODO Auto-generated method stub
         switch (event.getAction()) {
         case MotionEvent.ACTION_DOWN:
             mLastX = event.getX();
             break;
         case MotionEvent.ACTION_MOVE:
             mCurrentX = event.getX();
             mDeltX = (int) (mCurrentX - mLastX);
             // 如果开关开着向左滑动，或者开关关着向右滑动（这时候是不需要处理的）
             if ((mSwitchOn && mDeltX < 0) || (!mSwitchOn && mDeltX > 0)) {
                 mFlag = true;
                 mDeltX = 0;
             }

             if (Math.abs(mDeltX) > mMoveLength) {
                 mDeltX = mDeltX > 0 ? mMoveLength : - mMoveLength;
             }
             invalidate();
             return true;
         case MotionEvent.ACTION_UP:
             if (Math.abs(mDeltX) > 0 && Math.abs(mDeltX) < mMoveLength / 2) {
                 mDeltX = 0;
                 invalidate();
                 return true;
             } else if (Math.abs(mDeltX) > mMoveLength / 2 && Math.abs(mDeltX) <= mMoveLength) {
                 mDeltX = mDeltX > 0 ? mMoveLength : -mMoveLength;
                 mSwitchOn = !mSwitchOn;
                 if(mListener != null) {
                     mListener.onChange(this, mSwitchOn);
                 }
                 invalidate();
                 mDeltX = 0;
                 return true;
             } else if(mDeltX == 0 && mFlag) {
                 //这时候得到的是不需要进行处理的，因为已经move过了
                 mDeltX = 0;
                 mFlag = false;
                 return true;
             }
             return super.onTouchEvent(event);
         default:
             break;
         }
         invalidate();
         return super.onTouchEvent(event);
     }

     public void setOnChangeListener(OnChangeListener listener) {
         mListener = listener;
     }

     public interface OnChangeListener {
         public void onChange(SwitchButton sb, boolean state);
     }

     @Override
     public void onClick(View v) {
         // TODO Auto-generated method stub
         mDeltX = mSwitchOn ? mMoveLength : -mMoveLength;
         mSwitchOn = !mSwitchOn;
         if(mListener != null) {
             mListener.onChange(this, mSwitchOn);
         }
         invalidate();
         mDeltX = 0;
     }
 }

MainActivity：

 package com.example.switchbutton;


 import com.example.switchbutton.SwitchButton.OnChangeListener;

 import android.app.Activity;
 import android.os.Bundle;
 import android.util.Log;
 import android.view.Menu;
 import android.widget.Toast;

 public class MainActivity extends Activity {

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);

         SwitchButton sb = (SwitchButton) findViewById(R.id.wiperSwitch1);
         sb.setOnChangeListener(new OnChangeListener() {

             @Override
             public void onChange(SwitchButton sb, boolean state) {
                 // TODO Auto-generated method stub
                 Log.d("switchButton", state ? "开":"关");
                 Toast.makeText(MainActivity.this, state ? "开":"关", Toast.LENGTH_SHORT).show();
             }
         });
     }

     @Override
     public boolean onCreateOptionsMenu(Menu menu) {
         // Inflate the menu; this adds items to the action bar if it is present.
         getMenuInflater().inflate(R.menu.main, menu);
         return true;
     }
 }

activity_main.xml:

 <LinearLayout 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:orientation="vertical"
     android:paddingBottom="@dimen/activity_vertical_margin"
     android:paddingLeft="@dimen/activity_horizontal_margin"
     android:paddingRight="@dimen/activity_horizontal_margin"
     android:paddingTop="@dimen/activity_vertical_margin" >

     <ImageView
         android:id="@+id/imageView"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content" />
     <com.example.switchbutton.SwitchButton
         android:id="@+id/wiperSwitch1"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_marginLeft="100dip" />
 </LinearLayout>

主要的代码在switchbutton类中，代码有什么不足还希望大家多提提意见，自己很少写。

参考：http://stackoverflow.com/questions/11838022/how-to-paint-with-alpha

            http://blog.csdn.net/zenip/article/details/8766263