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android - 工作完成后无法停止工作人员 (ListenableWorker) 任务

问题描述

我似乎找不到停止我的工人任务的正确方法。我正在调用.set(Result.success());我的ResolvableFuture<Result>，但它从未onStopped()在我的班级中触发，并且其他订阅的回调似乎在我的工作人员中仍然处于活动状态。

在我连接到 BLE 设备后调用Result.success()后，它仍然会保持对onConnectionStateChange内部connectGatt()函数的活动引用。

即使在操作系统强行停止我的工作人员之后，它似乎也没有调用onStopped()，因为我不记得在日志中看到过它。

即使在创建了新工作人员之后，我仍然会在旧工作人员内部获得更新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");
    }

}

标签： androidworker

解决方案

请注意，ListenableWorker.onStopped()只有当工作人员被取消或任务被系统抢占时，才会调用该方法。如果工作人员已成功完成，onStop()则不会调用。该onStop() 文档告诉：

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onStop()即使worker成功完成也可以调用callback，但这是一个错误，将来会修复。看看这个帖子：为什么 Android Worker 成功完成并调用 onStopped()

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