当蓝牙在安卓棒棒糖上关闭时应用程序崩溃

Question

>我有一个 BroadcastReceiver 可以检测蓝牙状态的变化并相应地执行操作 - 当蓝牙打开时，它会打开信标的监控服务.当蓝牙关闭时，它会停止监控服务。这发生在Nexus 5上。接收器如下

public class BluetoothReceiver extends BroadcastReceiver {
public void onReceive(Context context, Intent intent) {
    String action = intent.getAction();
    if (BluetoothAdapter.ACTION_STATE_CHANGED.equals(action)) {
        // If Bluetooth is switched on
        if (intent.getIntExtra(BluetoothAdapter.EXTRA_STATE, -1)
                == BluetoothAdapter.STATE_ON) {
            //Start the beacon detection service
            if (EmployeeSignupManager.getEmployeeUUIDFromSharedPreference(context) != null) {
                // Register Receiver
                new AttendanceManager().startBroadCastReceiverForBeaconDetection(context);
                // Start Service
                SO.startBeaconServices(true);
            }
        }

        // If Bluetooth is switched off
        else if (intent.getIntExtra(BluetoothAdapter.EXTRA_STATE, -1)
                == BluetoothAdapter.STATE_OFF) {
            //Stop the beacon detection service
            if (EmployeeSignupManager.getEmployeeUUIDFromSharedPreference(context) != null) {
                // Unregister Receiver
                new AttendanceManager().stopBroadCastReceiverForBeaconDetection(context);
                // Stop Service
                SO.startBeaconServices(false);
            }
        }
    }
}

}

以下是堆栈跟踪：

java.lang.IllegalStateException: BT Adapter is not turned ON
        at android.bluetooth.le.BluetoothLeUtils.checkAdapterStateOn(BluetoothLeUtils.java:136)
        at android.bluetooth.le.BluetoothLeScanner.stopScan(BluetoothLeScanner.java:144)
        at org.altbeacon.beacon.service.scanner.CycledLeScannerForLollipop.deferScanIfNeeded(CycledLeScannerForLollipop.java:148)
        at org.altbeacon.beacon.service.scanner.CycledLeScanner.scanLeDevice(CycledLeScanner.java:163)
        at org.altbeacon.beacon.service.scanner.CycledLeScannerForLollipop$1.run(CycledLeScannerForLollipop.java:139)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5221)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

我写了这个：

 beaconManager.bind(this) 

其中 beaconManager 是类 BeaconManager（org.altbeacon.beacon） 的对象。 在服务连接回调中，我从数据库获取信标信息并开始监控过程：

Region region = new Region(beacon.getBeaconName(), Identifier.parse(beacon.getProximityUUID()), Identifier.parse(String.valueOf(beacon.getMajor())), Identifier.parse(String.valueOf(beacon.getMinor())));
    if (isStartingSevices) {
        try {
            System.out.println("Test notification Started monitoring beacon for region" + beacon.getBeaconName());
            if(isBluetoothEnabled()) {
                beaconManager.startMonitoringBeaconsInRegion(region);
            }
        } catch (RemoteException e) {
        }
    } else {
        try {
            System.out.println("Test notification stopped monitoring beacon for region" + beacon.getBeaconName());
            beaconManager.stopMonitoringBeaconsInRegion(region);
        } catch (RemoteException e) {
        }
    }

Answer 1

您可以在停止扫描之前检查蓝牙适配器状态，如下所示：

if (scanner != null && mLeScannerCallback != null && 
    mBluetoothAdapter.getState() == BluetoothAdapter.STATE_ON)

Answer 2

这是因为您在BT适配器关闭时尝试使用BT适配器，因此出现错误：BT适配器未打开

您应该检查BT在使用功能时是否打开：stopScan或startScan。您正在尝试在蓝牙LeScanner类的第144行中使用stopScan。因此，在运行此行之前，请首先检查BT是否打开。

要检查BT是否打开，您可以使用此方法：

public static boolean isBluetoothAvailable() {
        final BluetoothAdapter bluetoothAdapter = 
        BluetoothAdapter.getDefaultAdapter();
        return (bluetoothAdapter != null &&
                bluetoothAdapter.isEnabled() &&
                bluetoothAdapter.getState() == BluetoothAdapter.STATE_ON);
}

按键：BT = 蓝牙

参考：我自己在另一个类似问题的回答：https://stackoverflow.com/a/45730618/7403656