[英]java.lang.NullPointerException: Attempt to read from field 'long org.opencv.core.Mat.nativeObj' on a null object reference
I am new to openCV and android. 我是openCV和android的新手。 I am trying to load an image from Resources using bitmap and process the image using open CV. 我试图使用位图从资源中加载图像,并使用打开的CV处理图像。 It gave me this error: 它给了我这个错误:
java.lang.NullPointerException:
Attempt to read from field 'long org.opencv.core.Mat.nativeObj' on a null object reference
Code: 码:
Bitmap bm = BitmapFactory.decodeResource(getResources(),R.drawable.a1);
((ImageView)findViewById(R.id.imageView)).setImageBitmap(bm);
Mat trainImage = new Mat(bm.getHeight(),bm.getWidth(),CvType.CV_32S);
Utils.bitmapToMat(bm,trainImage);
if(trainImage.empty()){
Log.e(TAG,"Empty image");
}
else{
Log.e(TAG,"Image Loaded");
}
Imgproc.cvtColor(trainImage, trainGray, Imgproc.COLOR_RGBA2GRAY);
Here is the Exception message: 这是异常消息:
E/SVM: Image Loaded
D/AndroidRuntime: Shutting down VM
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.pragyan.facefeatures, PID: 3308
java.lang.NullPointerException: Attempt to read from field 'long org.opencv.core.Mat.nativeObj' on a null object reference
at org.opencv.imgproc.Imgproc.cvtColor(Imgproc.java:1724)
at com.example.pragyan.facefeatures.ExtractFeature.trainSvm(ExtractFeature.java:242)
at com.example.pragyan.facefeatures.ExtractFeature.onOptionsItemSelected(ExtractFeature.java:313)
at android.app.Activity.onMenuItemSelected(Activity.java:2885)
at android.support.v4.app.FragmentActivity.onMenuItemSelected(FragmentActivity.java:403)
at android.support.v7.app.AppCompatActivity.onMenuItemSelected(AppCompatActivity.java:189)
at android.support.v7.view.WindowCallbackWrapper.onMenuItemSelected(WindowCallbackWrapper.java:100)
at android.support.v7.app.AppCompatDelegateImplV7.onMenuItemSelected(AppCompatDelegateImplV7.java:663)
at android.support.v7.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:811)
at android.support.v7.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:152)
at android.support.v7.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:958)
at android.support.v7.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:948)
at android.support.v7.view.menu.MenuPopupHelper.onItemClick(MenuPopupHelper.java:191)
at android.widget.AdapterView.performItemClick(AdapterView.java:305)
at android.widget.AbsListView.performItemClick(AbsListView.java:1146)
at android.widget.AbsListView$PerformClick.run(AbsListView.java:3053)
at android.widget.AbsListView$3.run(AbsListView.java:3860)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Can anyone tell me how to fix this. 谁能告诉我如何解决此问题。 The image is loaded successfully and it still gives a NullPointerException
. 图像已成功加载,并且仍然提供NullPointerException
。
I think you've not initialized the Mat trainGray
. 我认为您尚未初始化Mat trainGray
。 Try the following. 尝试以下方法。
Mat trainGray = new Mat();
Imgproc.cvtColor(trainImage, trainGray, Imgproc.COLOR_RGBA2GRAY);
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