Android微信右滑退出功能的实现代码

public class Main3Activity extends AppCompatActivity {
 /**
  * DecorView左边滑出间距占屏幕宽度PRESENT_TO_FINISH时表示用户需要退出当前Activity
  */
 private static final float PRESENT_TO_FINISH = 0.3f;
 /**
  * 用户距离左边MIN_EDGE_DISTANCE内拖动有效
  */
 private static final int MIN_EDGE_DISTANCE = 100;
 /**
  * 屏幕宽度
  */
 private static float mScreenW = -1;
 /**
  * 用户计算用户在屏幕滑动的距离
  */
 private float mStartX = 0;
 /**
  * 当前是否允许拖动
  */
 private boolean mIsScrollEnable = false;
 /**
  * 当前Activity的DecorView
  */
 private View mDecorView;
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main3);
  // 初始化
  mDecorView = getWindow().getDecorView();
  if (mScreenW == -1) {
   DisplayMetrics metrics = new DisplayMetrics();
   getWindowManager().getDefaultDisplay()
     .getMetrics(metrics);
   mScreenW = metrics.widthPixels;
  }
 }
 @Override
 public boolean onTouchEvent(MotionEvent event) {
  if (event.getAction() == MotionEvent.ACTION_DOWN) {
   mStartX = event.getX();
   if (mStartX  PRESENT_TO_FINISH &＃63; (int) -mScreenW : 0;
   ValueAnimator animator = ValueAnimator.ofInt(mDecorView.getScrollX(), targetX);
   animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
    @Override
    public void onAnimationUpdate(ValueAnimator animation) {
     mDecorView.scrollTo((Integer) animation.getAnimatedValue(), 0);
    }
   });
   animator.addListener(new Animator.AnimatorListener() {
    @Override
    public void onAnimationStart(Animator animation) {
    }
    @Override
    public void onAnimationEnd(Animator animation) {
     if (targetX == -mScreenW) {
      finish();
     }
    }
    @Override
    public void onAnimationCancel(Animator animation) {
    }
    @Override
    public void onAnimationRepeat(Animator animation) {
    }
   });
   animator.start();
  }
  return super.onTouchEvent(event);
 }
}