Android 推门效果

public class MainActivity extends RelativeLayout{

    private Scroller scroller;
    private Context context;
    private int width;
    private int height;
    private ImageView imageView;

    private int mLastDownY = 0;  

    private int mCurryY;  

    private int mDelY;  

    private boolean mCloseFlag = false;  

    public Main_skip(Context context, AttributeSet attrs) {
        super(context, attrs);
        this.context = context;
        initView();
    }

    private void initView(){
        // 这个Interpolator你可以设置别的 我这里选择的是有弹跳效果的Interpolator
        BounceInterpolator interpolator = new BounceInterpolator();
        scroller = new Scroller(context,interpolator);

        WindowManager manager = (WindowManager) context
                .getSystemService(Context.WINDOW_SERVICE);
        DisplayMetrics metrics = new DisplayMetrics();
        manager.getDefaultDisplay().getMetrics(metrics);
        width = metrics.widthPixels;
        height = metrics.heightPixels;

        // 这里你一定要设置成透明背景,不然会影响你看到底层布局
        this.setBackgroundColor(Color.argb(0, 0, 0, 0));
        imageView = new ImageView(context);
        LayoutParams params = new LayoutParams(LayoutParams.MATCH_PARENT
                , LayoutParams.MATCH_PARENT);
        imageView.setLayoutParams(params);
        imageView.setScaleType(ScaleType.FIT_XY);
        imageView.setImageResource(R.drawable.a);
        addView(imageView);

    }

    public void setBGimg(int resID){
        imageView.setImageResource(resID);
    }

    public void setBGimg(Drawable drawable){
        imageView.setImageDrawable(drawable);
    }

    // 推动门的动画
    public void setAnimation(int startY, int dy, int duration){
        scroller.startScroll(0, startY, 0, dy, duration);
        invalidate();
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN:
            mLastDownY = (int) event.getY();
            System.err.println("ACTION_DOWN=" + mLastDownY);
            return true;
        case MotionEvent.ACTION_MOVE:
            mCurryY = (int) event.getY();
            System.err.println("ACTION_MOVE=" + mCurryY);
            mDelY = mCurryY - mLastDownY;
            if(mDelY < 0 ){
                scrollTo(0, -mDelY);
                 System.err.println("-------------  " + mDelY);
            }
            break;
        case MotionEvent.ACTION_UP:
            mCurryY = (int) event.getY();
            mDelY = mCurryY - mLastDownY;
            if(mDelY < 0){
                if(Math.abs(mDelY)>height/2){
                    setAnimation(this.getScrollY(), height, 450);
                    mCloseFlag = true;
                }else{
                    setAnimation(this.getScrollY(), -this.getScrollY(), 1000);
                }
            }
            break;

        default:
            break;
        }
        return super.onTouchEvent(event);
    }

    @Override
    public void computeScroll() {
        if(scroller.computeScrollOffset()){
            scrollTo(scroller.getCurrX(), scroller.getCurrY());
            // 不要忘记更新界面
            postInvalidate();
        }else {
            if (mCloseFlag) {
                this.setVisibility(View.GONE);
            }
        }
        super.computeScroll();
    }

}