circular reveal animation

CircularRevealAnimation.java

/**
     * On Lollipop+ perform a circular reveal animation (an expanding circular mask) when showing
     * the search panel.
     */
    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    private void doEnterAnim() {
        // Fade in a background scrim as this is a floating window. We could have used a
        // translucent window background but this approach allows us to turn off window animation &
        // overlap the fade with the reveal animation – making it feel snappier.
        View scrim = findViewById(R.id.scrim);
        scrim.animate()
                .alpha(1f)
                .setDuration(500L)
                .setInterpolator(
                        AnimationUtils.loadInterpolator(this, android.R.interpolator.fast_out_slow_in))
                .start();

        // Next perform the circular reveal on the search panel
        final View searchPanel = findViewById(R.id.search_panel);
        if (searchPanel != null) {
            // We use a view tree observer to set this up once the view is measured & laid out
            searchPanel.getViewTreeObserver().addOnPreDrawListener(
                    new ViewTreeObserver.OnPreDrawListener() {
                @Override
                public boolean onPreDraw() {
                    searchPanel.getViewTreeObserver().removeOnPreDrawListener(this);
                    // As the height will change once the initial suggestions are delivered by the
                    // loader, we can't use the search panels height to calculate the final radius
                    // so we fall back to it's parent to be safe
                    int revealRadius = ((ViewGroup) searchPanel.getParent()).getHeight();
                    // Center the animation on the top right of the panel i.e. near to the
                    // search button which launched this screen.
                    Animator show = ViewAnimationUtils.createCircularReveal(searchPanel,
                        searchPanel.getRight(), searchPanel.getTop(), 0f, revealRadius);
                    show.setDuration(250L);
                    show.setInterpolator(AnimationUtils.loadInterpolator(SearchActivity.this,
                            android.R.interpolator.fast_out_slow_in));
                    show.start();
                    return false;
                }
            });
        }
    }

    /**
     * On Lollipop+ perform a circular animation (a contracting circular mask) when hiding the
     * search panel.
     */
    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    private void doExitAnim() {
        final View searchPanel = findViewById(R.id.search_panel);
        // Center the animation on the top right of the panel i.e. near to the search button which
        // launched this screen. The starting radius therefore is the diagonal distance from the top
        // right to the bottom left
        int revealRadius = (int) Math.sqrt(Math.pow(searchPanel.getWidth(), 2)
                + Math.pow(searchPanel.getHeight(), 2));
        // Animating the radius to 0 produces the contracting effect
        Animator shrink = ViewAnimationUtils.createCircularReveal(searchPanel,
                searchPanel.getRight(), searchPanel.getTop(), revealRadius, 0f);
        shrink.setDuration(200L);
        shrink.setInterpolator(AnimationUtils.loadInterpolator(SearchActivity.this,
                android.R.interpolator.fast_out_slow_in));
        shrink.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                searchPanel.setVisibility(View.INVISIBLE);
                ActivityCompat.finishAfterTransition(SearchActivity.this);
            }
        });
        shrink.start();

        // We also animate out the translucent background at the same time.
        findViewById(R.id.scrim).animate()
                .alpha(0f)
                .setDuration(200L)
                .setInterpolator(
                        AnimationUtils.loadInterpolator(SearchActivity.this,
                                android.R.interpolator.fast_out_slow_in))
                .start();
    }