我正在尝试在较旧的 API 版本上启动前台服务。使用 API 26+

Question

我需要启动我的应用服务前台。我的代码在 API 级别 26 和更高级别上运行良好，但不适用于较旧的 API 级别。在旧版本上，服务显示在正在运行的服务中，但不发送启动通知。我需要对我的代码进行哪些更改，为什么不起作用？

public void onCreate() {
        super.onCreate();
        messageIntent.setAction(getString(R.string.receiver_receive));



        NotificationCompat.Builder builder = new NotificationCompat.Builder(this, NOTIFICATION_CHANNEL_ID_DEFAULT)
                .setOngoing(false).setSmallIcon(R.drawable.ic_launcher).setPriority(Notification.PRIORITY_MIN);

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
            NotificationChannel notificationChannel = new NotificationChannel(NOTIFICATION_CHANNEL_ID_DEFAULT,
                    NOTIFICATION_CHANNEL_ID_DEFAULT, NotificationManager.IMPORTANCE_LOW);
            notificationChannel.setDescription(NOTIFICATION_CHANNEL_ID_DEFAULT);
            notificationChannel.setSound(null, null);
            notificationManager.createNotificationChannel(notificationChannel);
            startForeground(1, builder.build());
        }

    }

启动服务

protected void onStart() {
        super.onStart();
        // Bind to LocalService
        Intent intent = new Intent(this, SocketService.class);
        bindService(intent, serviceConnection, Context.BIND_AUTO_CREATE);

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O)
            ContextCompat.startForegroundService(this, new Intent(this, SocketService.class));
        else
            this.startService(new Intent(this, SocketService.class));
    }

Answer 1

在 else 语句中为以下 api 启动服务。

if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
    // only for newer versions
      Intent pushIntent = new Intent(this, ClassName.class);
      startForegroundService(pushIntent);
} else {
      Intent pushIntent = new Intent(this, ClassName.class);
      startService(pushIntent);
}

Answer 2

方法ContextCompat.startForegroundService(...)已经包含if块：

public static void startForegroundService(@NonNull Context context, @NonNull Intent intent) {
    if (Build.VERSION.SDK_INT >= 26) {
        context.startForegroundService(intent);
    } else {
        // Pre-O behavior.
        context.startService(intent);
    }
}

只需致电ContextCompat.startForegroundService(this, pushIntent)。

你需要将startForeground移到if块之外：

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
    ...        
}
startForeground(1, builder.build());

另外，不要忘记在旧 API 上调用 notificationManagerCompat.notify(NOTIFICATION_ID, notification)（如果通知未自动显示）。 NOTIFICATION_ID 不能为零！！！

Answer 3

为api低于26的设备编写代码与if语句中编写的代码相同，但不包括通知通道部分，因为版本低于26的设备不支持通知通道

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        // you had written code for device version greater than O
    } else {
       //You need to write code for device with lower version here
    }