Android，服务：获取BluetoothManager返回null

Question

希望你能帮助我解决这个问题。

我正在将我的蓝牙代码从活动转移到服务，但它无法在服务中的构造函数中获取BluetoothManager。它保持返回null。你知道为什么吗？

public class BluetoothService extends Service { 

private Handler handler; 
private static int secondsBetweenScans; 
private BluetoothAdapter mBluetoothAdapter; 

private Handler mHandler; 

private boolean mScanning; 

private Map<String, Integer> foundBluetoothDevicesAndTheirSignalStrengths; 
private ArrayList<String> foundBluetoothDevices; 

// Stops scanning after 10 seconds. 
private static final long SCAN_DURATION = 2000; 

@Override 
public IBinder onBind(Intent intent) { 
    return null; 
} 

public BluetoothService() { 
    Log.i("KontaktBluetoothService", "BluetoothService initialized"); 

    // Initializes Bluetooth adapter. 
    final BluetoothManager mbluetoothManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE); <-- Returns null 
    mBluetoothAdapter = mbluetoothManager.getAdapter(); 

    . 
    . 
    . 

} 

@Override 
public int onStartCommand(Intent intent, int flags, int startId) { 
    . 
    . 
    . 

} 

private void scanLeDevice(final boolean enable) { 
    . 
    . 
    . 
} 

// Device scan callback. 
private BluetoothAdapter.LeScanCallback mLeScanCallback = new BluetoothAdapter.LeScanCallback() { 

    @Override 
    public void onLeScan(final BluetoothDevice device, int rssi, byte[] scanRecord) { 
     . 
     . 
     . 
    }; 

} 

这是我收到

07-04 20:29:02.134: D/AndroidRuntime(27710): Shutting down VM 
07-04 20:29:02.134: W/dalvikvm(27710): threadid=1: thread exiting with uncaught exception (group=0x41ce1700) 
07-04 20:29:02.159: E/AndroidRuntime(27710): FATAL EXCEPTION: main 
07-04 20:29:02.159: E/AndroidRuntime(27710): java.lang.RuntimeException: Unable to instantiate service fo.vera.kontakt.BluetoothService: java.lang.NullPointerException 
07-04 20:29:02.159: E/AndroidRuntime(27710): at android.app.ActivityThread.handleCreateService(ActivityThread.java:2671) 
07-04 20:29:02.159: E/AndroidRuntime(27710): at android.app.ActivityThread.access$1700(ActivityThread.java:159) 
07-04 20:29:02.159: E/AndroidRuntime(27710): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1404) 
07-04 20:29:02.159: E/AndroidRuntime(27710): at android.os.Handler.dispatchMessage(Handler.java:99) 
07-04 20:29:02.159: E/AndroidRuntime(27710): at android.os.Looper.loop(Looper.java:176) 
07-04 20:29:02.159: E/AndroidRuntime(27710): at android.app.ActivityThread.main(ActivityThread.java:5419) 
07-04 20:29:02.159: E/AndroidRuntime(27710): at java.lang.reflect.Method.invokeNative(Native Method) 
07-04 20:29:02.159: E/AndroidRuntime(27710): at java.lang.reflect.Method.invoke(Method.java:525) 
07-04 20:29:02.159: E/AndroidRuntime(27710): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1046) 
07-04 20:29:02.159: E/AndroidRuntime(27710): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:862) 
07-04 20:29:02.159: E/AndroidRuntime(27710): at dalvik.system.NativeStart.main(Native Method) 
07-04 20:29:02.159: E/AndroidRuntime(27710): Caused by: java.lang.NullPointerException 
07-04 20:29:02.159: E/AndroidRuntime(27710): at android.content.ContextWrapper.getSystemService(ContextWrapper.java:526) 
07-04 20:29:02.159: E/AndroidRuntime(27710): at fo.vera.kontakt.BluetoothService.<init>(BluetoothService.java:38) 
07-04 20:29:02.159: E/AndroidRuntime(27710): at java.lang.Class.newInstanceImpl(Native Method) 
07-04 20:29:02.159: E/AndroidRuntime(27710): at java.lang.Class.newInstance(Class.java:1130) 
07-04 20:29:02.159: E/AndroidRuntime(27710): at android.app.ActivityThread.handleCreateService(ActivityThread.java:2668) 
07-04 20:29:02.159: E/AndroidRuntime(27710): ... 10 more 

这里的清单文件中的错误：

<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
    package="fo.vera.kontakt" 
    android:versionCode="1" 
    android:versionName="1.0" > 

    <uses-sdk 
     android:minSdkVersion="8" 
     android:targetSdkVersion="19" /> 

    <uses-permission android:name="android.permission.BLUETOOTH"/> 
    <uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/> 

    <uses-feature android:name="android.hardware.bluetooth_le" android:required="false"/> 

    <application 
     android:allowBackup="true" 
     android:icon="@drawable/ic_launcher" 
     android:label="@string/app_name" 
     android:theme="@style/AppTheme" > 
     <activity 
      android:name="fo.vera.kontakt.MainActivity" 
      android:configChanges="orientation|keyboardHidden|screenSize" 
      android:label="@string/app_name"> 
      <intent-filter> 
       <action android:name="android.intent.action.MAIN" /> 

       <category android:name="android.intent.category.LAUNCHER" /> 
      </intent-filter> 
     </activity> 

     <service 
      android:name="fo.vera.kontakt.BluetoothService" 
      android:enabled="true" 
      android:exported="false" > 
     </service> 
    </application> 

</manifest> 

任何帮助表示赞赏！

Answer 1

不要在构造函数中这样做。将其移入onCreate()。

该服务的上下文尚未完全建立。