我在Android O操作系统上使用服务类。
我计划在后台使用服务。
Android文档指出
如果你的应用程序的API级别为26或更高，系统会对使用或创建后台服务施加限制，除非应用程序本身在前台。如果应用程序需要创建前台服务，应用程序应该调用startForegroundService()。
如果使用startForegroundService()，服务抛出以下错误。
Context.startForegroundService() did not then call
Service.startForeground()
这有什么问题?
当前回答
好吧，我注意到的一些东西可能也会对其他人有所帮助。这是严格的测试，看看我是否能找出如何解决我所看到的事件。为了简单起见，假设我有一个从演示者调用这个的方法。
context.startForegroundService(new Intent(context, TaskQueueExecutorService.class));
try {
Thread.sleep(10000);
} catch (InterruptedException e) {
e.printStackTrace();
}
这将导致同样的错误。在方法完成之前，服务不会启动，因此服务中没有onCreate()。
So even if you update the UI off the main thread, IF you have anything that might hold up that method after it, it won't start on time and give you the dreaded Foreground Error. In my case we were loading some things onto a queue and each called startForegroundService, but some logic was involved with each in the background. So if the logic took too long to finish that method since they were called back to back, crash time. The old startService just ignored it and went on it's way and since we called it each time, the next round would finish up.
这让我想知道，如果我从后台线程调用服务，它是否可以在启动时完全绑定并立即运行，因此我开始试验。即使这样不会立即启动，它也不会崩溃。
new Handler(Looper.getMainLooper()).post(new Runnable() {
public void run() {
context.startForegroundService(new Intent(context,
TaskQueueExecutorService.class));
try {
Thread.sleep(10000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
});
我不会假装知道为什么它没有崩溃，尽管我怀疑这迫使它等待，直到主线程能够及时处理它。我知道将它绑定到主线程并不理想，但由于我的使用是在后台调用它，所以我并不真正关心它是否等待完成而不是崩溃。
其他回答
我在Pixel 3和Android 11中遇到了一个问题，当我的服务运行得很短时，前台通知没有被取消。
在stopForeground() stopSelf()之前添加100ms的延迟似乎有所帮助。
人们在这里写道，stopprospect()应该在stopSelf()之前被调用。我不能确认，但我猜它不会费心去做。
public class AService extends Service {
@Override
public void onCreate() {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
startForeground(
getForegroundNotificationId(),
channelManager.buildBackgroundInfoNotification(getNotificationTitle(), getNotificationText()),
ServiceInfo.FOREGROUND_SERVICE_TYPE_DATA_SYNC);
} else {
startForeground(getForegroundNotificationId(),
channelManager.buildBackgroundInfoNotification(getNotificationTitle(), getNotificationText())
);
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
startForeground();
if (hasQueueMoreItems()) {
startWorkerThreads();
} else {
stopForeground(true);
stopSelf();
}
return START_STICKY;
}
private class WorkerRunnable implements Runnable {
@Override
public void run() {
while (getItem() != null && !isLoopInterrupted) {
doSomething(getItem())
}
waitALittle();
stopForeground(true);
stopSelf();
}
private void waitALittle() {
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
Android O API 26的问题
如果你立即停止服务(所以你的服务实际上并没有真正运行(措辞/理解)，并且你在ANR间隔之下，你仍然需要在stopSelf之前调用start前台
https://plus.google.com/116630648530850689477/posts/L2rn4T6SAJ5
尝试了这种方法，但它仍然创建一个错误:-
if (Util.SDK_INT > 26) {
mContext.startForegroundService(playIntent);
} else {
mContext.startService(playIntent);
}
我正在使用这个，直到错误被解决
mContext.startService(playIntent);
此错误也发生在Android 8+服务时。start前台(int id, Notification Notification)在id设置为0时被调用。
id int:该通知的标识符，根据NotificationManager。通知(int、通知);一定不是0。
服务
class TestService : Service() {
override fun onCreate() {
super.onCreate()
Log.d(TAG, "onCreate")
val nBuilder = NotificationCompat.Builder(this, "all")
.setSmallIcon(R.drawable.ic_launcher_foreground)
.setContentTitle("TestService")
.setPriority(NotificationCompat.PRIORITY_DEFAULT)
startForeground(1337, nBuilder.build())
}
override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
val rtn = super.onStartCommand(intent, flags, startId)
if (intent?.action == STOP_ACTION) {
Log.d(TAG, "onStartCommand -> STOP")
stopForeground(true)
stopSelf()
} else {
Log.d(TAG, "onStartCommand -> START")
}
return rtn
}
override fun onDestroy() {
Log.d(TAG, "onDestroy")
super.onDestroy()
}
override fun onBind(intent: Intent?): IBinder? = null
companion object {
private val TAG = "TestService"
private val STOP_ACTION = "ly.zen.test.TestService.ACTION_STOP"
fun start(context: Context) {
ContextCompat.startForegroundService(context, Intent(context, TestService::class.java))
}
fun stop(context: Context) {
val intent = Intent(context, TestService::class.java)
intent.action = STOP_ACTION
ContextCompat.startForegroundService(context, intent)
}
}
}
测试人员
val nChannel = NotificationChannel("all", "All", NotificationManager.IMPORTANCE_NONE)
val nManager = getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
nManager.createNotificationChannel(nChannel)
start_test_service.setOnClickListener {
TestService.start(this@MainActivity)
TestService.stop(this@MainActivity)
}
结果
D/TestService: onCreate
D/TestService: onStartCommand -> START
D/TestService: onStartCommand -> STOP
D/TestService: onDestroy
更新onStartCommand中的数据(…)
上绑定（...
与onCreate(…)相比，onBind(…)是一个更好的生命周期事件来初始化start前台，因为onBind(…)传递了一个Intent，其中可能包含初始化服务所需的Bundle中的重要数据。然而，这是不必要的，因为onStartCommand(…)是在服务第一次创建或后续多次调用时调用的。
onStartCommand（...）
onStartCommand(…)中的start前台是很重要的，以便在服务创建后更新它。
当ContextCompat.startForegroundService(…)在服务创建后被调用时，onBind(…)和onCreate(…)没有被调用。因此，更新后的数据可以通过Intent Bundle传递到onStartCommand(…)来更新服务中的数据。
样本
我使用这个模式在Coinverse加密货币新闻应用程序中实现PlayerNotificationManager。
Activity / Fragment.kt
context?.bindService(
Intent(context, AudioService::class.java),
serviceConnection, Context.BIND_AUTO_CREATE)
ContextCompat.startForegroundService(
context!!,
Intent(context, AudioService::class.java).apply {
action = CONTENT_SELECTED_ACTION
putExtra(CONTENT_SELECTED_KEY, contentToPlay.content.apply {
audioUrl = uri.toString()
})
})
AudioService.kt
private var uri: Uri = Uri.parse("")
override fun onBind(intent: Intent?) =
AudioServiceBinder().apply {
player = ExoPlayerFactory.newSimpleInstance(
applicationContext,
AudioOnlyRenderersFactory(applicationContext),
DefaultTrackSelector())
}
override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
intent?.let {
when (intent.action) {
CONTENT_SELECTED_ACTION -> it.getParcelableExtra<Content>(CONTENT_SELECTED_KEY).also { content ->
val intentUri = Uri.parse(content.audioUrl)
// Checks whether to update Uri passed in Intent Bundle.
if (!intentUri.equals(uri)) {
uri = intentUri
player?.prepare(ProgressiveMediaSource.Factory(
DefaultDataSourceFactory(
this,
Util.getUserAgent(this, getString(app_name))))
.createMediaSource(uri))
player?.playWhenReady = true
// Calling 'startForeground' in 'buildNotification(...)'.
buildNotification(intent.getParcelableExtra(CONTENT_SELECTED_KEY))
}
}
}
}
return super.onStartCommand(intent, flags, startId)
}
// Calling 'startForeground' in 'onNotificationStarted(...)'.
private fun buildNotification(content: Content): Unit? {
playerNotificationManager = PlayerNotificationManager.createWithNotificationChannel(
this,
content.title,
app_name,
if (!content.audioUrl.isNullOrEmpty()) 1 else -1,
object : PlayerNotificationManager.MediaDescriptionAdapter {
override fun createCurrentContentIntent(player: Player?) = ...
override fun getCurrentContentText(player: Player?) = ...
override fun getCurrentContentTitle(player: Player?) = ...
override fun getCurrentLargeIcon(player: Player?,
callback: PlayerNotificationManager.BitmapCallback?) = ...
},
object : PlayerNotificationManager.NotificationListener {
override fun onNotificationStarted(notificationId: Int, notification: Notification) {
startForeground(notificationId, notification)
}
override fun onNotificationCancelled(notificationId: Int) {
stopForeground(true)
stopSelf()
}
})
return playerNotificationManager.setPlayer(player)
}
