ViewOverlay 看似挺陌生的，其實android在4.3的時候就已經供給了，它是view上面的的一個浮層，這個浮層與當前View檢視大小一致，可以理解一個上下兩層的樓房，但是上層的內容並不影響整個佈局.

API：新增覆蓋

 /**
     * Adds a Drawable to the overlay. The bounds of the drawable should be relative to
     * the host view. Any drawable added to the overlay should be removed when it is no longer
     * needed or no longer visible.
     *
     * @param drawable The Drawable to be added to the overlay. This drawable will be
     * drawn when the view redraws its overlay.
     * @see #remove(Drawable)
     */
    public void add(Drawable drawable) {
        mOverlayViewGroup.add(drawable);
    }
 

    /**
     * Removes the specified Drawable from the overlay.
     *
     * @param drawable The Drawable to be removed from the overlay.
     * @see #add(Drawable)
     */
    public void remove(Drawable drawable) {
        mOverlayViewGroup.remove(drawable);
    }

  /**
     * Removes all content from the overlay.
     */
    public void clear() {
        mOverlayViewGroup.clear();
    }
 

 boolean isEmpty() {
        return mOverlayViewGroup.isEmpty();
    }

add(view) ;remove(view) 新增浮層檢視和移除浮沉檢視

 * @param view The View to be added to the overlay. The added view will be
     * drawn when the overlay is drawn.
     * @see #remove(View)
     * @see ViewOverlay#add(Drawable)
     */
    public void add(View view) {
        mOverlayViewGroup.add(view);
    }

    /**
     * Removes the specified View from the overlay.
     *
     * @param view The View to be removed from the overlay.
     * @see #add(View)
     * @see ViewOverlay#remove(Drawable)
     */
    public void remove(View view) {
        mOverlayViewGroup.remove(view);
    }
 

最大的作用就是穿越層次

下面將會給出例子:

1:移動的範圍 左邊擴充套件範圍為整個窗體，而右邊預設屬於父親範圍大小

 private void overlayWindow(final View v) {
        if (Build.VERSION.SDK_INT < 18) return;
        final ViewGroup group = ((ViewGroup) getWindow().getDecorView());
        group.getOverlay().add(v);

        //簡單位移動畫
        ObjectAnimator anim = ObjectAnimator.ofFloat(v, "translationY", group.getHeight());
        anim.setDuration(2000);
        anim.addListener(new Animator.AnimatorListener() {
            @Override
            public void onAnimationStart(Animator animation) {

            }

            @Override
            public void onAnimationEnd(Animator animation) {
                group.getOverlay().remove(v);
            }

            @Override
            public void onAnimationCancel(Animator animation) {
                group.getOverlay().remove(v);
            }

            @Override
            public void onAnimationRepeat(Animator animation) {

            }
        });
        anim.start();
    }

    private void animWiew(View v) {
        ObjectAnimator anim = ObjectAnimator.ofFloat(v, "translationY", 15 * (v.getHeight()));
        anim.setDuration(2000);
        anim.start();
    }

可以看到左邊的移動返回為整個窗體，而右邊移動返回屬於紅色區域（預設父親窗體大小)

例子2:展現view預設的移動範圍，是他父親的大小範圍

 private void overlayWindow2(final View v) {
        if (Build.VERSION.SDK_INT < 18) return;
        final ViewGroup group = (ViewGroup) v.getParent();
        ObjectAnimator anim = ObjectAnimator.ofFloat(v, "translationY", group.getHeight());
        anim.setDuration(2000);
        anim.start();
    }

例子3： 凌波微步的效果:

 /**
     * 先展示一個消失動畫
     * <p/>
     * 再在窗體中位移
     * <p/>
     * 凌波微步的效果
     *
     * @param v
     */
    private void CombinationOverlay(final View v) {
        if (Build.VERSION.SDK_INT < 18) return;

        ObjectAnimator fade = ObjectAnimator.ofFloat(button3, "alpha", 1f, 0f);
        fade.setDuration(1000);


        fade.addListener(new Animator.AnimatorListener() {
            @Override
            public void onAnimationStart(Animator animation) {

            }

            @Override
            public void onAnimationEnd(Animator animation) {
                FrameLayout fram_greent = (FrameLayout) findViewById(R.id.fram_greent);
                v.setAlpha(1.0f);
                fram_greent.getOverlay().add(v);

                final ViewGroup group = ((ViewGroup) getWindow().getDecorView());
                ObjectAnimator anim = ObjectAnimator.ofFloat(v, "translationY", -group.getHeight());
                anim.setDuration(2000);
                anim.addListener(new Animator.AnimatorListener() {
                    @Override
                    public void onAnimationStart(Animator animation) {

                    }

                    @Override
                    public void onAnimationEnd(Animator animation) {
                        group.getOverlay().remove(v);
                    }

                    @Override
                    public void onAnimationCancel(Animator animation) {
                        group.getOverlay().remove(v);
                    }

                    @Override
                    public void onAnimationRepeat(Animator animation) {

                    }
                });
                anim.start();

            }

            @Override
            public void onAnimationCancel(Animator animation) {

            }

            @Override
            public void onAnimationRepeat(Animator animation) {

            }
        });
        fade.start();


    }