空对象引用onReceive BroadcastReceiver

我正在使用两个活动，主要的和摄影机之一。在mainActivity中，我打电话startActivity（new Intent（this，CameraActivity））;空对象引用onReceive BroadcastReceiver

现在，相机活动开始时，的onCreate（）是：

@Override 
public void onCreate(Bundle savedInstanceState) { 

    super.onCreate(savedInstanceState); 
    setContentView(R.layout.camera_preview); 
    View myView= (View) findViewById(R.id.camera_previeww); 
    myView.setSystemUiVisibility(View.SYSTEM_UI_FLAG_HIDE_NAVIGATION); 

    cameraID= Camera.CameraInfo.CAMERA_FACING_FRONT; 
    mCamera=openCamera(cameraID); 
    mCamera.startPreview(); 

    IntentFilter filter = new IntentFilter(); 
    filter.addAction(Tabbed.BROADCAST_ACTION_TABBED); 
    LocalBroadcastManager bm = LocalBroadcastManager.getInstance(this); 
    bm.registerReceiver(mBroadcastReceiver, filter); 


    // Create our Preview view and set it as the content of our activity. 
    mPreview = new CameraPreview(this, mCamera); 
    FrameLayout preview = (FrameLayout) this.findViewById(R.id.camera_previeww); 
    preview.addView(mPreview); 
}

的openCamera（INT cameraID）方法是：

public Camera openCamera(int cameraIDD){ 
     Camera c=null; 
     try{ 
      c=Camera.open(cameraIDD); 
     }catch (Exception e){ 
      Log.d("Camera Activity", e.getMessage()); 
     } 
      return c; 

    }

而且我使用BroadcastReceiver like：

 private BroadcastReceiver mBroadcastReceiver = new BroadcastReceiver() { 
    @Override 
    public void onReceive(Context context, Intent intent) { 

     byte [] data=new byte[3]; 
     if (intent.getAction().equals(Tabbed.BROADCAST_ACTION_TABBED)) { 
      data = intent.getByteArrayExtra(Tabbed.EXTRA_PARAM_BYTE); 
     } 
     if (data[FINGER]==MIDDLE_FINGER && data[TYPE]==SINGLE_TAP){ 
      //switchCamera(); 
      //releaseCamera(); 
      //mCamera=Camera.open(); 
     } 
     else if (data[FINGER]==MIDDLE_FINGER && data[TYPE]==DOUBLE_TAP){ 
      // HAVE TO GO BACK 
      kill_activity(); 
     } 
     else if (data[FINGER]==INDEX_FINGER && data[TYPE]==SINGLE_TAP){ 
      mCamera.takePicture(null, null, mPicture); 
     } 

    // kill activity 

    } 
};

还有一些其他的方法：

 @Override 
protected void onPause() { 
    super.onPause(); 
    //releaseCamera();    // release the camera immediately on pause event 
} 

private void releaseCamera(){ 
    if (mCamera != null){ 
     mCamera.release();  // release the camera for other applications 
     mCamera = null; 
    } 
} 
void kill_activity() 
{ 
    mCamera.stopPreview(); 
    mCamera.setPreviewCallback(null); 
    releaseCamera(); 
    finish(); 
}

这里是崩溃：

FATAL EXCEPTION: main 
                  Process: com.etu.goglove, PID: 6008 
                  java.lang.NullPointerException: Attempt to invoke virtual method 'void android.hardware.Camera.takePicture(android.hardware.Camera$ShutterCallback, android.hardware.Camera$PictureCallback, android.hardware.Camera$PictureCallback)' on a null object reference 
                   at com.etu.goglove.CameraActivity$2.onReceive(CameraActivity.java:155) 
                   at android.support.v4.content.LocalBroadcastManager.executePendingBroadcasts(LocalBroadcastManager.java:297) 
                   at android.support.v4.content.LocalBroadcastManager.access$000(LocalBroadcastManager.java:46) 
                   at android.support.v4.content.LocalBroadcastManager$1.handleMessage(LocalBroadcastManager.java:116) 
                   at android.os.Handler.dispatchMessage(Handler.java:102) 
                   at android.os.Looper.loop(Looper.java:154) 
                   at android.app.ActivityThread.main(ActivityThread.java:6119) 
                   at java.lang.reflect.Method.invoke(Native Method) 
                   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
                   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

有了这一切，我想，当我接收广播意图拍照。所以，在我的活动开始后，我打开mCamera，当我收到意图时，我会拍照或回来。第一次，我可以拍照，然后完成我的活动。如果我尝试从mainActivity重新启动cameraActivity，则调用startActivity（intent），在onCreate（）摄像机已打开并且它不为空（与调试器一起检查），但是这一次，当我进入的onReceive（）方法，mCamera永远是空的，所以我得到mCamera空对象引用！（当我试图做mCamera.takePicture（））不知道如何...

谢谢！

来源

2017-02-08 Isabel Gasperini

可以张贴崩溃日志 – Gautam

@Gautam添加它 –

崩溃在CameraActivity.java上线155，检查一次你的代码 – Gautam

您应该取消注册mBroadcastReceiver。

void kill_activity() 
{ 
    mCamera.stopPreview(); 
    mCamera.setPreviewCallback(null); 
    releaseCamera(); 
    bm.unregisterReceiver(mBroadcastReceiver); 
    finish(); 
}

来源

2017-02-09 08:30:09 mychemicalro

private BroadcastReceiver mBroadcastReceiver = new BroadcastReceiver() { 
    @Override 
    public void onReceive(Context context, Intent intent) { 

     byte [] data=new byte[3]; 
     if (intent!=null && intent.getAction().equals(Tabbed.BROADCAST_ACTION_TABBED)) { 
      data = intent.getByteArrayExtra(Tabbed.EXTRA_PARAM_BYTE); 

     if (data[FINGER]==MIDDLE_FINGER && data[TYPE]==SINGLE_TAP){ 
      //switchCamera(); 
      //releaseCamera(); 
      //mCamera=Camera.open(); 
     } 
     else if (data[FINGER]==MIDDLE_FINGER && data[TYPE]==DOUBLE_TAP){ 
      // HAVE TO GO BACK 
      kill_activity(); 
     } 
     else if (data[FINGER]==INDEX_FINGER && data[TYPE]==SINGLE_TAP){ 
      mCamera.takePicture(null, null, mPicture); 
     } 
} 
    // kill activity 

    } 
};

来源

2017-02-08 09:53:40 Gautam

我应该从这个理解什么？ –

add intent！= null in receiver – Gautam

没有改变 –

空对象引用onReceive BroadcastReceiver

回答

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