工作完成后无法停止工作线程 (ListenableWorker) 任务

Question

我似乎找不到停止工作线程任务的正确方法。我在ResolvableFuture<Result>上调用.set(Result.success());，但它从未在我的班级中触发onStopped()，并且其他订阅的回调似乎在我的工作线程中仍然活跃。

• 我的工作线程启动并尝试查找特定的 BLE 设备
• 它连接到该设备并尝试退出并显示Result.success()
• 如果工作人员运行超过 3 分钟，则尝试退出。

在我连接到 BLE 设备后调用Result.success()后，它仍将在函数内部保留对onConnectionStateChange的活动引用connectGatt().

即使在操作系统强行停止我的工人之后，它似乎甚至没有调用onStopped()，因为我不记得在日志中看到过它。

即使在创建新工作线程之后，我仍然会在旧工作线程内部获得更新onConnectionStateChange

package test;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothGatt;
import android.bluetooth.BluetoothGattCallback;
import android.bluetooth.BluetoothManager;
import android.bluetooth.BluetoothProfile;
import android.bluetooth.le.ScanCallback;
import android.bluetooth.le.ScanFilter;
import android.bluetooth.le.ScanResult;
import android.bluetooth.le.ScanSettings;
import android.content.Context;
import android.os.Build;
import android.os.Handler;
import android.util.Log;
import androidx.annotation.NonNull;
import androidx.annotation.RequiresApi;
import androidx.concurrent.futures.ResolvableFuture;
import androidx.work.ListenableWorker;
import androidx.work.WorkerParameters;
import com.google.common.util.concurrent.ListenableFuture;
import java.util.ArrayList;
import java.util.List;
import static android.bluetooth.BluetoothDevice.TRANSPORT_LE;
import static android.os.Build.VERSION_CODES.M;
public class BluetoothScanWorker extends ListenableWorker  {
private String TAG = "BluetoothScanWorker";
private BluetoothAdapter bluetoothAdapter;
private ResolvableFuture<Result> mFuture;

public BluetoothScanWorker(@NonNull Context context, @NonNull WorkerParameters workerParams) {
super(context, workerParams);
}
@NonNull
@Override
public ListenableFuture<Result> startWork() {
mFuture = ResolvableFuture.create();
Log.d(TAG ,"startWork()");
if (Build.VERSION.SDK_INT >= M) {
ScanSettings settings = (new ScanSettings.Builder().setScanMode(ScanSettings.SCAN_MODE_LOW_POWER)).build();
List<ScanFilter> filters_v2 = new ArrayList<>();
ScanFilter scanFilter = new ScanFilter.Builder()
.setDeviceAddress("B8:27:EB:B9:5C:FC")
.build();
filters_v2.add(scanFilter);
BluetoothManager bluetoothManager =
(BluetoothManager) this.getApplicationContext().getSystemService(Context.BLUETOOTH_SERVICE);
bluetoothAdapter = bluetoothManager.getAdapter();
bluetoothAdapter.getBluetoothLeScanner().startScan(filters_v2, settings, leScanCallback); // Scan for every BLE device matching my filter
Handler handler = new Handler();
handler.postDelayed(new Runnable() {
@Override
public void run() {
endWork();
}
}, 3*60*1000); // End worker after 3 minutes
}
return mFuture;
}

private void endWork(){
if (Build.VERSION.SDK_INT >= M) {
Log.d(TAG, "END WORK");
bluetoothAdapter.getBluetoothLeScanner().stopScan(leScanCallback);
mFuture.set(Result.success());
}
}

@RequiresApi(M)
private ScanCallback leScanCallback = new ScanCallback() { // Called when I find my BLE device
@Override
public void onScanResult(int callbackType, ScanResult result) {
Log.d(TAG ,"onScanResult: " + result.getDevice().toString());
bluetoothAdapter.getBluetoothLeScanner().stopScan(this);
result.getDevice().connectGatt(getApplicationContext(), true, new BluetoothGattCallback() { // Connect to my BLE device
@Override
public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
if (newState == BluetoothProfile.STATE_CONNECTED) {
if (status == BluetoothGatt.GATT_SUCCESS) {
Log.d(TAG ,"GATT connected successfully");
endWork();
}
} else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
Log.d(TAG ,"GATT disconnected");
endWork();
}
}
},TRANSPORT_LE);
}
};

@Override
public void onStopped() {
Log.d(TAG, "Work service stopped");
}
}

Answer 1

请注意，仅当工作线程被取消或任务被系统抢占时，才会调用ListenableWorker.onStopped()方法。如果辅助角色已成功完成，则不会调用onStop()。onStop()文档指出：

当此 Worker 被告知停止时，将调用此方法。 这可能是由于用户的明确取消信号， 或者因为系统已决定抢占任务。...

有时，即使工作线程成功完成onStop()也可以调用回调，但这是一个将来会修复的错误。看看这篇文章：为什么 Android Worker 成功完成并调用 onStop()