[英]Null object reference onReceive BroadcastReceiver
我正在使用两个活动,主要活动和相机活动。 在mainActivity中,我调用startActivity(new Intent(this,CameraActivity));
现在,当摄像机活动开始时, onCreate()为:
@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);
}
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;
}
我也使用的是BroadcastReceiver:
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
}
};
和其他一些方法:
@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)
有了这些,我想在收到广播意向时拍照。 因此,在我的活动开始之后,我打开mCamera,当我收到意向书时,我进行了拍照或返回。 第一次,我可以拍照,然后完成活动。 如果我尝试从mainActivity重新启动cameraActivity,调用onActiv ()相机中的startActivity(intent)处于打开状态,并且它不为null(已通过调试器检查),但是这一次,当我进入onReceive()方法时, mCamera始终为null,因此我在mCamera上获得了一个空对象引用!(当我尝试执行mCamera.takePicture()时 )不知道如何...
谢谢!
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
}
};
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