我的 android 应用程序中有 4 个活动。创建第一个活动时，它会在后台播放音乐。现在，当用户从第一个活动转到第二个活动时，我希望歌曲继续播放而不会中断。只有当用户离开应用程序时，歌曲才会停止。
现在音乐在我退出一项活动时停止，并在下一项活动中从头开始。
【问题讨论】：
Service并从那里控制MediaPlayer实例
标签： android android-music-player
将播放器作为静态参考保持在后台。然后让它知道您是在应用程序内还是在应用程序外移动。这是我将如何做到的。为此，我使用了一个名为 DJ 的类。
public class DJ {
private static MediaPlayer player;
private static boolean keepMusicOn;
public static void iAmIn(Context context){
if (player == null){
player = MediaPlayer.create(context, R.raw.music1);
player.setLooping(true);
try{
player.prepare();
}
catch (IllegalStateException e){}
catch (IOException e){}
}
if(!player.isPlaying()){
player.start();
}
keepMusicOn= false;
}
public static void keepMusicOn(){
keepMusicOn= true;
}
public static void iAmLeaving(){
if(!keepMusicOn){
player.pause();
}
}
}
现在从你的活动中像这样给 DJ 打电话。（让他知道你是否想继续播放音乐）
public void onPause() {
super.onPause();
DJ.iAmLeaving();
}
public void onResume(){
super.onResume();
DJ.iAmIn(this);
}
public void buttonOnClick(View view){
DJ.keepMusicOn();
Intent intent = new Intent(this, TheOtherActivity.class);
startActivity(intent);
}
【讨论】：
我是这样做的，我对结果很满意：
第一次创建服务：
public class LocalService extends Service
{
// This is the object that receives interactions from clients. See RemoteService for a more complete example.
private final IBinder mBinder = new LocalBinder();
private MediaPlayer player;
/**
* Class for clients to access. Because we know this service always runs in
* the same process as its clients, we don't need to deal with IPC.
*/
public class LocalBinder extends Binder
{
LocalService getService()
{
return LocalService.this;
}
}
@Override
public void onCreate()
{
}
@Override
public int onStartCommand(Intent intent, int flags, int startId)
{
// We want this service to continue running until it is explicitly stopped, so return sticky.
return START_STICKY;
}
@Override
public void onDestroy()
{
destroy();
}
@Override
public IBinder onBind(Intent intent)
{
return mBinder;
}
public void play(int res)
{
try
{
player = MediaPlayer.create(this, res);
player.setLooping(true);
player.setVolume(0.1f, 0.1f);
player.start();
}
catch(Exception e)
{
e.printStackTrace();
}
}
public void pause()
{
if(null != player && player.isPlaying())
{
player.pause();
player.seekTo(0);
}
}
public void resume()
{
try
{
if(null != player && !player.isPlaying())
{
player.start();
}
}
catch(Exception e)
{
e.printStackTrace();
}
}
public void destroy()
{
if(null != player)
{
if(player.isPlaying())
{
player.stop();
}
player.release();
player = null;
}
}
}
第 2 次strong>，创建一个基础活动，并在你希望从中播放背景音乐的女巫中扩展所有活动：
public class ActivityBase extends Activity
{
private Context context = ActivityBase.this;
private final int [] background_sound = { R.raw.azilum_2, R.raw.bg_sound_5 };
private LocalService mBoundService;
private boolean mIsBound = false;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
doBindService();
}
@Override
protected void onStart()
{
super.onStart();
try
{
if(null != mBoundService)
{
Random rand = new Random();
int what = background_sound[rand.nextInt(background_sound.length)];
mBoundService.play(what);
}
}
catch(Exception e)
{
e.printStackTrace();
}
}
@Override
protected void onStop()
{
super.onStop();
basePause();
}
protected void baseResume()
{
try
{
if(null != mBoundService)
{
mBoundService.resume();
}
}
catch(Exception e)
{
e.printStackTrace();
}
}
protected void basePause()
{
try
{
if(null != mBoundService)
{
mBoundService.pause();
}
}
catch(Exception e)
{
e.printStackTrace();
}
}
private ServiceConnection mConnection = new ServiceConnection()
{
public void onServiceConnected(ComponentName className, IBinder service)
{
// This is called when the connection with the service has been
// established, giving us the service object we can use to
// interact with the service. Because we have bound to a explicit
// service that we know is running in our own process, we can
// cast its IBinder to a concrete class and directly access it.
mBoundService = ((LocalService.LocalBinder) service).getService();
if(null != mBoundService)
{
Random rand = new Random();
int what = background_sound[rand.nextInt(background_sound.length)];
mBoundService.play(what);
}
}
public void onServiceDisconnected(ComponentName className)
{
// This is called when the connection with the service has been
// unexpectedly disconnected -- that is, its process crashed.
// Because it is running in our same process, we should never
// see this happen.
mBoundService = null;
if(null != mBoundService)
{
mBoundService.destroy();
}
}
};
private void doBindService()
{
// Establish a connection with the service. We use an explicit
// class name because we want a specific service implementation that
// we know will be running in our own process (and thus won't be
// supporting component replacement by other applications).
Intent i = new Intent(getApplicationContext(), LocalService.class);
bindService(i, mConnection, Context.BIND_AUTO_CREATE);
mIsBound = true;
}
private void doUnbindService()
{
if (mIsBound)
{
// Detach our existing connection.
unbindService(mConnection);
mIsBound = false;
}
}
@Override
protected void onDestroy()
{
super.onDestroy();
doUnbindService();
}
}
就是这样，现在您在从 ActivityBase 扩展的所有活动中都有背景声音了。
您甚至可以通过调用 basePause()/baseResume() 来控制暂停/恢复功能。
不要忘记在清单中声明服务：
<service android:name="com.gga.screaming.speech.LocalService" />
【讨论】：
这个想法是您不应该播放活动本身的音乐。在 Android 上，活动和其他上下文具有生命周期。这意味着他们将活着……然后死去。而当他们死了，他们就不能再做任何事了。
因此，如果您想让音乐的寿命更长，就必须找到生命周期不止一个活动的东西。
最简单的解决方案是 Android 服务。你可以在这里找到一个好帖子：Android background music service
【讨论】：