Android服务已销毁，但没有无限循环

Question

Everybody!

I have a problem with my app (Xamarin.Android). I'm trying to write service which should scan Bluetooth devices:

[Service]
internal class BluetoothService : IntentService
{
    ...

    protected override void OnHandleIntent(Intent intent)
    {
        // Thats not working...
    }

    public override StartCommandResult OnStartCommand(Intent intent, StartCommandFlags flags, int startId)
    {

        _bluetoothAdapter = BluetoothAdapter.DefaultAdapter;

        ScanLeDeviceInLoop(true);

        return StartCommandResult.Sticky;
    }


    private async void ScanLeDeviceInLoop(bool enable)
    {
        await Task.Factory.StartNew(async () =>
        {
            if (enable == _loopScanningEnabled)
                return;

            _loopScanningEnabled = enable;

            while (_loopScanningEnabled)
            {
                _container.Clear();
                _bluetoothAdapter.StartLeScan(_leScanCallback);

                await Task.Factory.StartNew(() => System.Threading.Thread.Sleep((int)_scanPeriod.TotalMilliseconds));

                _bluetoothAdapter.StopLeScan(_leScanCallback);

                OnScanCompleted();
            }
        });
    }
} 

After OnStartCommand and ScanLeDeviceInLoop service call onDestroy. But I want to keep this service alive (thread with scanning is alive, but service not) and call StopService from UI to stop scanning. But I can't due to service is already stopped.

Any suggestion? Thanks.

Answer 1

IntentService are designed to perform finite units of work asynchronously.

They handle asynchronous requests (expressed as Intents ) on demand. Clients send requests through StartService(Intent) calls; the service is started as needed, handles each Intent in turn using a worker thread, and stops itself when it runs out of work.

You should not override OnStartCommand method for your IntentService . Instead, override OnHandleIntent(Intent) , which the system calls when the IntentService receives a start request.

In your situation service probably stops because he finished all the work in OnHandleIntent which is none.

I recommend you to use Service class, but remember that you should create your new thread manually, because Service unlike IntentService working on the main thread