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
我调用ContextCompat。startForegroundService(this, intent)然后启动服务
在服务onCreate中
@Override
public void onCreate() {
super.onCreate();
if (Build.VERSION.SDK_INT >= 26) {
String CHANNEL_ID = "my_channel_01";
NotificationChannel channel = new NotificationChannel(CHANNEL_ID,
"Channel human readable title",
NotificationManager.IMPORTANCE_DEFAULT);
((NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE)).createNotificationChannel(channel);
Notification notification = new NotificationCompat.Builder(this, CHANNEL_ID)
.setContentTitle("")
.setContentText("").build();
startForeground(1, notification);
}
}
其他回答
我也面临着同样的问题，花时间找到了一个解决方案，你可以尝试下面的代码。如果你使用服务，然后把这段代码放在onCreate，否则你使用意图服务，然后把这段代码放在onHandleIntent。
if (Build.VERSION.SDK_INT >= 26) {
String CHANNEL_ID = "my_app";
NotificationChannel channel = new NotificationChannel(CHANNEL_ID,
"MyApp", NotificationManager.IMPORTANCE_DEFAULT);
((NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE)).createNotificationChannel(channel);
Notification notification = new NotificationCompat.Builder(this, CHANNEL_ID)
.setContentTitle("")
.setContentText("").build();
startForeground(1, notification);
}
我一直在研究这个问题，这是我目前为止的发现。如果我们有类似这样的代码，就会发生崩溃:
MyForegroundService.java
public class MyForegroundService extends Service {
@Override
public void onCreate() {
super.onCreate();
startForeground(...);
}
}
MainActivity.java
Intent serviceIntent = new Intent(this, MyForegroundService.class);
startForegroundService(serviceIntent);
...
stopService(serviceIntent);
异常在以下代码块中抛出:
ActiveServices.java
private final void bringDownServiceLocked(ServiceRecord r) {
...
if (r.fgRequired) {
Slog.w(TAG_SERVICE, "Bringing down service while still waiting for start foreground: "
+ r);
r.fgRequired = false;
r.fgWaiting = false;
mAm.mAppOpsService.finishOperation(AppOpsManager.getToken(mAm.mAppOpsService),
AppOpsManager.OP_START_FOREGROUND, r.appInfo.uid, r.packageName);
mAm.mHandler.removeMessages(
ActivityManagerService.SERVICE_FOREGROUND_TIMEOUT_MSG, r);
if (r.app != null) {
Message msg = mAm.mHandler.obtainMessage(
ActivityManagerService.SERVICE_FOREGROUND_CRASH_MSG);
msg.obj = r.app;
msg.getData().putCharSequence(
ActivityManagerService.SERVICE_RECORD_KEY, r.toString());
mAm.mHandler.sendMessage(msg);
}
}
...
}
这个方法在MyForegroundService的onCreate()之前执行，因为Android在主线程处理程序上安排了服务的创建，但在BinderThread上调用了bringdownservicelock，这是一个竞争条件。这意味着MyForegroundService没有机会调用start前台，这将导致崩溃。
为了解决这个问题，我们必须确保在MyForegroundService的onCreate()之前不调用bringdownservicellocked。
public class MyForegroundService extends Service {
private static final String ACTION_STOP = "com.example.MyForegroundService.ACTION_STOP";
private final BroadcastReceiver stopReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
context.removeStickyBroadcast(intent);
stopForeground(true);
stopSelf();
}
};
@Override
public void onCreate() {
super.onCreate();
startForeground(...);
registerReceiver(
stopReceiver, new IntentFilter(ACTION_STOP));
}
@Override
public void onDestroy() {
super.onDestroy();
unregisterReceiver(stopReceiver);
}
public static void stop(Context context) {
context.sendStickyBroadcast(new Intent(ACTION_STOP));
}
}
通过使用粘性广播，我们确保广播不会丢失，stopReceiver在MyForegroundService的onCreate()中注册后立即接收到停止意图。此时我们已经调用了startForeground(…)。我们还必须删除这个粘滞的广播，以防止下一次stopReceiver被通知。
请注意，sendStickyBroadcast方法已弃用，我仅将其用作解决此问题的临时方法。
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
即使在Service中调用start前台之后，如果我们在onCreate调用之前调用stopService，它也会在某些设备上崩溃。 所以，我通过启动附加标志的服务来修复这个问题:
Intent intent = new Intent(context, YourService.class);
intent.putExtra("request_stop", true);
context.startService(intent);
并在onStartCommand中添加了一个检查，看看它是否已经开始停止:
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
//call startForeground first
if (intent != null) {
boolean stopService = intent.getBooleanExtra("request_stop", false);
if (stopService) {
stopSelf();
}
}
//Continue with the background task
return START_STICKY;
}
附注:如果服务没有运行，它将首先启动服务，这是一种开销。
当使用目标sdk 28或更高版本时，你必须为android 9设备添加如下权限，否则异常总是会发生:
<uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
