samples/devbytes/animation/SquashAndStretch/src/com/example/squashandstretch/SquashAndStretch.java

/*
 * Copyright (C) 2013 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.squashandstretch;

import android.animation.AnimatorSet;
import android.animation.ObjectAnimator;
import android.animation.PropertyValuesHolder;
import android.animation.ValueAnimator;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.AccelerateInterpolator;
import android.view.animation.DecelerateInterpolator;

/**
 * This example shows how to add some life to a view during animation by deforming the shape.
 * As the button "falls", it stretches along the line of travel. When it hits the bottom, it
 * squashes, like a real object when hitting a surface. Then the button reverses these actions
 * to bounce back up to the start.
 *
 * Watch the associated video for this demo on the DevBytes channel of developer.android.com
 * or on the DevBytes playlist in the androiddevelopers channel on YouTube at
 * https://www.youtube.com/playlist?list=PLWz5rJ2EKKc_XOgcRukSoKKjewFJZrKV0.
 */
public class SquashAndStretch extends Activity {

    private static final AccelerateInterpolator sAccelerator = new AccelerateInterpolator();
    private static final DecelerateInterpolator sDecelerator = new DecelerateInterpolator();

    ViewGroup mContainer = null;
    private static final long BASE_DURATION = 300;
    private long sAnimatorScale = 1;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        mContainer = (ViewGroup) findViewById(R.id.container);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }
    
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        if (item.getItemId() == R.id.menu_slow) {
            sAnimatorScale = item.isChecked() ? 1 : 5;
            item.setChecked(!item.isChecked());
        }
        return super.onOptionsItemSelected(item);
    }

    public void onButtonClick(View view) {
        long animationDuration = (long) (BASE_DURATION * sAnimatorScale);

        // Scale around bottom/middle to simplify squash against the window bottom
        view.setPivotX(view.getWidth() / 2);
        view.setPivotY(view.getHeight());
        
        // Animate the button down, accelerating, while also stretching in Y and squashing in X
        PropertyValuesHolder pvhTY = PropertyValuesHolder.ofFloat(View.TRANSLATION_Y,
                mContainer.getHeight() - view.getHeight());
        PropertyValuesHolder pvhSX = PropertyValuesHolder.ofFloat(View.SCALE_X, .7f);
        PropertyValuesHolder pvhSY = PropertyValuesHolder.ofFloat(View.SCALE_Y, 1.2f);
        ObjectAnimator downAnim = ObjectAnimator.ofPropertyValuesHolder(
                view, pvhTY, pvhSX, pvhSY);
        downAnim.setInterpolator(sAccelerator);
        downAnim.setDuration((long) (animationDuration * 2));

        // Stretch in X, squash in Y, then reverse
        pvhSX = PropertyValuesHolder.ofFloat(View.SCALE_X, 2);
        pvhSY = PropertyValuesHolder.ofFloat(View.SCALE_Y, .5f);
        ObjectAnimator stretchAnim =
                ObjectAnimator.ofPropertyValuesHolder(view, pvhSX, pvhSY);
        stretchAnim.setRepeatCount(1);
        stretchAnim.setRepeatMode(ValueAnimator.REVERSE);
        stretchAnim.setInterpolator(sDecelerator);
        stretchAnim.setDuration(animationDuration);
        
        // Animate back to the start
        pvhTY = PropertyValuesHolder.ofFloat(View.TRANSLATION_Y, 0);
        pvhSX = PropertyValuesHolder.ofFloat(View.SCALE_X, 1);
        pvhSY = PropertyValuesHolder.ofFloat(View.SCALE_Y, 1);
        ObjectAnimator upAnim =
                ObjectAnimator.ofPropertyValuesHolder(view, pvhTY, pvhSX, pvhSY);
        upAnim.setDuration((long) (animationDuration * 2));
        upAnim.setInterpolator(sDecelerator);

        AnimatorSet set = new AnimatorSet();
        set.playSequentially(downAnim, stretchAnim, upAnim);
        set.start();
    }
}