android实现QQ微信侧滑删除效果

import android.util.AttributeSet; import android.util.Log; import android.util.TypedValue; import android.view.MotionEvent; import android.view.View; import android.widget.LinearLayout; import android.widget.RelativeLayout; import android.widget.Scroller; import android.widget.TextView;    public class SlideView extends LinearLayout {      private static final String TAG = "SlideView";      private Context mContext;      // 用来放置所有view的容器    private LinearLayout mViewContent;      // 用来放置内置view的容器，比如删除 按钮    private RelativeLayout mHolder;      // 弹性滑动对象，提供弹性滑动效果    private Scroller mScroller;      // 滑动回调接口，用来向上层通知滑动事件    private OnSlideListener mOnSlideListener;      // 内置容器的宽度 单位：dp    private int mHolderWidth = 120;      // 分别记录上次滑动的坐标    private int mLastX = 0;    private int mLastY = 0;      // 用来控制滑动角度，仅当角度a满足如下条件才进行滑动：tan a = deltaX / deltaY > 2    private static final int TAN = 2;      public interface OnSlideListener {      // SlideView的三种状态：开始滑动，打开，关闭      public static final int SLIDE_STATUS_OFF = 0;      public static final int SLIDE_STATUS_START_SCROLL = 1;      public static final int SLIDE_STATUS_ON = 2;        public void onSlide(View view, int status);    }      public SlideView(Context context) {      super(context);      initView();    }      public SlideView(Context context, AttributeSet attrs) {      super(context, attrs);      initView();    }      private void initView() {      mContext = getContext();      // 初始化弹性滑动对象      mScroller = new Scroller(mContext);      // 设置其方向为横向      setOrientation(LinearLayout.HORIZONTAL);      // 将slide_view_merge加载进来      View.inflate(mContext, R.layout.slide_view_merge, this);      mViewContent = (LinearLayout) findViewById(R.id.view_content);      mHolderWidth = Math.round(TypedValue.applyDimension(          TypedValue.COMPLEX_UNIT_DIP, mHolderWidth, getResources()              .getDisplayMetrics()));    }      // 设置按钮的内容，也可以设置图标啥的，我没写    public void setButtonText(CharSequence text) {      ((TextView) findViewById(R.id.delete)).setText(text);    }      // 将view加入到ViewContent中    public void setContentView(View view) {      mViewContent.addView(view);    }      // 设置滑动回调    public void setOnSlideListener(OnSlideListener onSlideListener) {      mOnSlideListener = onSlideListener;    }      // 将当前状态置为关闭    public void shrink() {      if (getScrollX() != 0) {        this.smoothScrollTo(0, 0);      }    }      // 根据MotionEvent来进行滑动，这个方法的作用相当于onTouchEvent    // 如果你不需要处理滑动冲突，可以直接重命名，照样能正常工作    public void onRequireTouchEvent(MotionEvent event) {      int x = (int) event.getX();      int y = (int) event.getY();      int scrollX = getScrollX();      Log.d(TAG, "x=" + x + " y=" + y);        switch (event.getAction()) {      case MotionEvent.ACTION_DOWN: {        if (!mScroller.isFinished()) {          mScroller.abortAnimation();        }        if (mOnSlideListener != null) {          mOnSlideListener.onSlide(this,              OnSlideListener.SLIDE_STATUS_START_SCROLL);        }        break;      }      case MotionEvent.ACTION_MOVE: {        int deltaX = x - mLastX;        int deltaY = y - mLastY;        if (Math.abs(deltaX) < Math.abs(deltaY) * TAN) {          // 滑动不满足条件，不做横向滑动          break;        }          // 计算滑动终点是否合法，防止滑动越界        int newScrollX = scrollX - deltaX;        if (deltaX != 0) {          if (newScrollX < 0) {            newScrollX = 0;          } else if (newScrollX > mHolderWidth) {            newScrollX = mHolderWidth;          }          this.scrollTo(newScrollX, 0);        }        break;      }      case MotionEvent.ACTION_UP: {        int newScrollX = 0;        // 这里做了下判断，当松开手的时候，会自动向两边滑动，具体向哪边滑，要看当前所处的位置        if (scrollX - mHolderWidth * 0.75 > 0) {          newScrollX = mHolderWidth;        }        // 慢慢滑向终点        this.smoothScrollTo(newScrollX, 0);        // 通知上层滑动事件        if (mOnSlideListener != null) {          mOnSlideListener.onSlide(this,              newScrollX == 0 ? OnSlideListener.SLIDE_STATUS_OFF                  : OnSlideListener.SLIDE_STATUS_ON);        }        break;      }      default:        break;      }        mLastX = x;      mLastY = y;    }      private void smoothScrollTo(int destX, int destY) {      // 缓慢滚动到指定位置      int scrollX = getScrollX();      int delta = destX - scrollX;      // 以三倍时长滑向destX，效果就是慢慢滑动      mScroller.startScroll(scrollX, 0, delta, 0, Math.abs(delta) * 3);      invalidate();    }      @Override    public void computeScroll() {      if (mScroller.computeScrollOffset()) {        scrollTo(mScroller.getCurrX(), mScroller.getCurrY());        postInvalidate();      }    }    }