21.音频播放与单元测试

创建Soundpool
1.首先实现音频播放功能，这需要创建一个SoundPool对象，代码如下所示

public class BeatBox {
private static final String TAG = "BeatBox"；
private static final String SOUNDS_FOLDER ="sample_sounds"；
private static final int MAX_SOUNDS = 5；
private AssetManager mAssets;
private List<Sound> mSounds= new ArrayList<>()；
private SoundPool mSoundPool;
public BeatBox(Context context) {
mAssets = context.getAssets()；
// This old constructor is deprecated, but we need it for compatibility. mSoundPool = new SoundPool(MAX_SOUNDS, AudioManager.STREAM_MUSIC,0)；loadSounds()；
}
}

加载音频文件
2.在Sound类中添加mSoundId实例变量，并添加相应的getter方法和setter方法管理这些ID

public class Sound {
private String mAssetPath;
private String mName;
··.
private Integer mSoundId;
public String getName(){
return mName;
}
public Integer getSoundId(){
return mSoundId;
}
public void setSoundId(Integer soundId) {
mSoundId = soundId;
}
}

3.加载音频(BeatBox.java)

private void loadSounds(){
}
private void load(Sound sound) throws IOException{
AssetFileDescriptor afd = mAssets.openFd(sound.getAssetPath())；int soundId= mSoundPool.load(afd,1);
sound.setSoundId(soundId);
}
public list<Sound> getSounds(){
return mSounds;
}
}

4.载入全部音频文件（BeatBoxjava）

private void loadSounds(){
for (String filename: soundNames){
try {
String assetPath = SOUNDS FOLDER +"/"+ filename;
Sound sound = new Sound(assetPath)；
load(sound)；
mSounds.add(sound);
} catch (IOException ioe){
Log.e(TAG, "Could not load sound "+ filename, ioe)；
}
}
}

播放音频
5.播放音频（BeatBoxjava）

public BeatBox(Context context){
mAssets = context.getAssets()；
// This old constructor is deprecated but needed for compatibility mSoundPool= new SoundPool(MAX_SOUNDS,AudioManager.STREAM_MUSIC, 0);loadSounds();
}
public void play(Sound sound) {
Integer soundId = sound.getSoundId();
if (soundId == null){
return;
}
mSoundPool.play(soundId, 1.0f, 1.0f, 1, 0, 1.0f);
private void loadSounds() {

添加测试依赖
6.打开build.gradle文件，把依赖项作用范围从compile改为testCompile，代码如下所示

dependencies {
compile fileTree(include:['*.jar'],dir: 'libs'}
androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2'，{
exclude group:'com.android.support', module: 'support-annotations'
}}
compile 'com.android.support:appcompat-v7:24.2.0'
testCompile’junit:junit:4.12'
compile'com.android.support:recyclerview-v7:24.2.0
compile testCompile 'org.mockito:mockito-core:2.2.1'
compile testCompile 'org.hamcrest:hamcrest-junit:2.0.6.0'
}

创建测试类
7.创建一个用作JUnit测试的测试类。打开SoundViewModel.java文件，使用Command+Shifi+T(Ctrl+Shift+T)组合键。Android Studio尝试寻找这个类关联的测试类。如果找不到，它就会提示新建，如图所示
8.选择Create New Test…创建一个新测试类。测试库选择JUnit4，勾选setUp/@Before，其他保持默认设置，如图所示
实现测试类
9.空测试类（SoundViewModelTest.java）

public class SoundViewModelTest {
@Before
public void setUp() throws Exception {
}
}

使用虚拟依赖项
10.创建虚拟BeatBox对象（SoundViewModelTest.java）

public class SoundViewModelTest {
private BeatBox mBeatBox;
@Before
public void setUp() throws Exception {
mBeatBox = mock(BeatBox.class)；
}
}

11.创建SoundViewModel测试对象（SoundViewModelTest.java）

public class SoundViewModelTest {
private BeatBox mBeatBox;
private Sound mSound;
private SoundViewModel mSubject;
@Before
public void setUp() throws Exception{
mBeatBox = mock(BeatBox.class);
mSound = new Sound("assetPath");
mSubject = new SoundViewModel(mBeatBox);
mSubject.setSound(mSound);
}
}

编写测试方法
12.测试标题属性（SoundViewModelTest.java)

@Before
public voidsetUp()throws Exception {
mBeatBox = mock(BeatBox.class);
mSound = new Sound("assetPath");
mSubject = new SoundViewModel(mBeatBox);
mSubject.setSound(mSound);
}
@Test
public void exposesSoundNameAsTitle(){
assertThat(mSubject.getTitle()，is(mSound.getName()))；
}

测试对象交互
13.测试onButtonClicked()方法(SoundViewModelTest.java)

@Test
public void exposesSoundNameAsTitle(){
assertThat(mSubject.getTitle()，is(mSound.getName()));
}
@Test
public void callsBeatBoxPlayOnButtonClicked(){
mSubject.onButtonClicked();
}
}

14.创建onButtonClicked()方法（SoundViewModel.java)

public void setSound(Sound sound) {
mSound = sound;
notifyChange()；
}
public void onButtonClicked(){
}
}

15.调用verify(Object)方法，确认onButtonClicked()方法调用了BeatBox.play(Sound)方法,代码如下

assertThat(mSubject.getTitle(),is(mSound.getName()));
}
@Test
public void callsBeatBoxPlayOnButtonClicked(){
mSubject.onButtonClicked()；
verify(mBeatBox).play(mSound)；
}
}

16.实现onButtonClicked()方法(SoundViewModel.java)

public void setSound(Sound sound){
mSound = sound;
notifyChange();
}
public void onButtonClicked(){
mBeatBox.play(mSound);
}
}

数据绑定回调

17.按钮要响应事件还差最后一步：关联按钮对象和onButtonClicked()方法。和前面使用数据绑定关联数据和UI一样，你也可以使用lambda表达式，让数据绑定帮忙关联按钮和点击监听器，代码如下所示，在布局文件里，添加数据绑定lambda表达式，让按钮对象和onButtonClicked()方法关联起来

<Button
android:layout_width="match_parent"
android:layout_height="120dp"
android:onClick="@f(）-> viewModel.onButtonClicked()J"
android:text="@fviewModel.title)"
tools:text="Sound name"/>

释放音频

18.BeatBox应用可用了，应调用SoundPool.release()方法释放SoundPool，添加BeatBox.release()清理方法

public class BeatBox{
public void play(Sound sound){
}
public void release(){
nSoundPool.release()； 21
}
}

同样，在BeatBoxFragment中，也完成释放

public class BeatBoxFragment extends Fragment{
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState){
}
6Override
public void onDestroy(){
super,onDestroy();
mBeatBox.release();
}
}

设备旋转和对象保存

19.保留fragment,调用setRetainInstance(true)(BeatBoxFragment.java)

public static BeatBoxFragment newInstance(){
return new BeatBoxFragment();
}
@Override
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setRetainInstance(true)；
mBeatBox = new BeatBox(getActivity());
}
aOverride
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){

20.准备就绪，实机演示 ，运行结果：

点击即可播放多种吓人音频，强烈建议半夜播放