Android自定义View实现自动吸附功能

import android.content.Context;
import android.graphics.Canvas;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.animation.DecelerateInterpolator;
import android.widget.ImageView;

public class AdsorbentViews extends ImageView {
 
 private int maxWidth;
  private int maxHeight;
  private int viewWidth;
  private int viewHeight;
  private float downx;
  private float downy;
  private Context mContext;
  public CustomViews(Context context) {
    this(context, null);
  }
 
  public CustomViews(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
  }
 
  public CustomViews(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    mContext = context;
  }
  @Override
  protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    DisplayMetrics outMetrics = new DisplayMetrics();
    WindowManager windowManager = (WindowManager) mContext.getSystemService(Context.WINDOW_SERVICE);
    windowManager.getDefaultDisplay().getRealMetrics(outMetrics);
    //屏幕的宽度
    maxWidth = outMetrics.widthPixels;
    //屏幕的高度
    maxHeight = outMetrics.heightPixels;
    /**
     * 控件的宽高
     */
    viewWidth = canvas.getWidth();
    viewHeight = canvas.getHeight();
  }
  @Override
  public boolean onTouchEvent(MotionEvent event) {
    switch (event.getAction()) {
      case MotionEvent.ACTION_DOWN:
        clearAnimation();
        downx = event.getX();
        downy = event.getY();
        return true;
      case MotionEvent.ACTION_MOVE:
        float moveX = event.getRawX() - downx;
        float moveY = event.getRawY() - downy;
        moveX = moveX < 0 ? 0 : (moveX + viewWidth > maxWidth) ? (maxWidth - viewWidth) : moveX;
        moveY = moveY < 0 ? 0 : (moveY + viewHeight) > maxHeight ? (maxHeight - viewHeight) : moveY;
        this.setY(moveY);
        this.setX(moveX);
        return true;
      case MotionEvent.ACTION_UP:
        //做吸附效果
        float centerX = getX() + viewWidth / 2;
        if (centerX > maxWidth/2){
          //靠右吸附
          animate().setInterpolator(new DecelerateInterpolator())
              .setDuration(500)
              .x(maxWidth-viewWidth)
              .y(maxHeight-viewHeight)
              .start();
        }else {
          animate().setInterpolator(new DecelerateInterpolator())
              .setDuration(500)
              .x(0)
              .y(maxHeight-viewHeight)
              .start();
        }
        return true;
      default:
        return super.onTouchEvent(event);
    }
  }
}