android theme install,java - 尝试在空对象引用上调用虚拟方法'android.content.res.Resources $ Theme android.content.C...

我想在Android应用程序内部的图像上运行一些OpenCv过滤器。 我遇到了一个错误，我似乎无法找到它的起源。

堆栈跟踪：

java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources$Theme android.content.Context.getTheme()' on a null object reference

at android.app.AlertDialog.resolveDialogTheme(AlertDialog.java:222)

at android.app.AlertDialog$Builder.(AlertDialog.java:452)

at org.opencv.android.BaseLoaderCallback.onPackageInstall(BaseLoaderCallback.java:90)

at org.opencv.android.AsyncServiceHelper.InstallService(AsyncServiceHelper.java:117)

at org.opencv.android.AsyncServiceHelper.initOpenCV(AsyncServiceHelper.java:33)

at org.opencv.android.OpenCVLoader.initAsync(OpenCVLoader.java:100)

at project.fragment.OpenCvTestFragment.onCreateView(OpenCvTestFragment.java:94)

at android.support.v4.app.Fragment.performCreateView(Fragment.java:1974)

at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067)

at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1252)

at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:742)

at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1617)

at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:517)

at android.os.Handler.handleCallback(Handler.java:739)

at android.os.Handler.dispatchMessage(Handler.java:95)

at android.os.Looper.loop(Looper.java:148)

at android.app.ActivityThread.main(ActivityThread.java:5417)

at java.lang.reflect.Method.invoke(Native Method)

at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)

at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

我的代码：(OpenCvTestFragment.java)

import android.content.Context;

import android.graphics.Bitmap;

import android.net.Uri;

import android.os.Bundle;

import android.support.v4.app.Fragment;

import android.util.Log;

import android.view.LayoutInflater;

import android.view.MotionEvent;

import android.view.View;

import android.view.ViewGroup;

import android.widget.Button;

import android.widget.ImageView;

import org.opencv.android.BaseLoaderCallback;

import org.opencv.android.CameraBridgeViewBase;

import org.opencv.android.LoaderCallbackInterface;

import org.opencv.android.OpenCVLoader;

import org.opencv.android.Utils;

import org.opencv.core.Core;

import org.opencv.core.CvType;

import org.opencv.core.Mat;

import org.opencv.core.Size;

import org.opencv.imgproc.Imgproc;

import org.opencv.imgcodecs.Imgcodecs;

import java.io.IOException;

import team_excellence.growup.R;

public class OpenCvTestFragment extends Fragment implements CameraBridgeViewBase.CvCameraViewListener2, View.OnTouchListener {

private OnOpenCvTestInteractionListener mListener;

private View view;

private ImageView imgView1;

private ImageView imgView2;

public OpenCvTestFragment() {

}

public static OpenCvTestFragment newInstance(String param1, String param2) {

OpenCvTestFragment fragment = new OpenCvTestFragment();

Bundle args = new Bundle();

fragment.setArguments(args);

return fragment;

}

private static final String TAG = "OCVSample::Activity";

private BaseLoaderCallback mOpenCVCallBack = new BaseLoaderCallback(getActivity()) {

@Override

public void onManagerConnected(int status) {

switch (status) {

case LoaderCallbackInterface.SUCCESS: {

Log.i(TAG, "OpenCV loaded successfully");

}

break;

default: {

super.onManagerConnected(status);

}

break;

}

}

};

@Override

public View onCreateView(LayoutInflater inflater, ViewGroup container,

Bundle savedInstanceState) {

if (container == null) {

return null;

}

view = inflater.inflate(R.layout.fragment_open_cv_test, container, false);

final ImageView imgView1 = (ImageView) view.findViewById(R.id.ocvImage1);

imgView1.setImageResource(R.drawable.img1);

ImageView imgView2 = (ImageView) view.findViewById(R.id.ocvImage2);

imgView1.setImageResource(R.drawable.img2);

final Button contoursButton = (Button) view.findViewById(R.id.contoursButton);

contoursButton.setOnClickListener(new View.OnClickListener(){

public void onClick(View v) {

try {

applyContoursFilter("img1");

} catch (IOException e) {

e.printStackTrace();

}

}

});

OpenCVLoader.initAsync(OpenCVLoader.OPENCV_VERSION_2_4_8, getContext(),

mOpenCVCallBack);

return view;

}

public void onButtonPressed(Uri uri) {

if (mListener != null) {

mListener.onOpenCvTestInteraction(uri);

}

}

@Override

public void onAttach(Context context) {

super.onAttach(context);

if (context instanceof OnOpenCvTestInteractionListener) {

mListener = (OnOpenCvTestInteractionListener) context;

} else {

throw new RuntimeException(context.toString()

+ " must implement OnOpenCvTestInteractionListener");

}

}

@Override

public void onDetach() {

super.onDetach();

mListener = null;

}

@Override

public void onCameraViewStarted(int width, int height) {

}

@Override

public void onCameraViewStopped() {

}

@Override

public Mat onCameraFrame(CameraBridgeViewBase.CvCameraViewFrame inputFrame) {

return null;

}

@Override

public boolean onTouch(View v, MotionEvent event) {

return false;

}

public interface OnOpenCvTestInteractionListener {

void onOpenCvTestInteraction(Uri uri);

}

public void applyContoursFilter(String resName) throws IOException {

Mat matImg = convertImageToMat(resName);

Mat matResult = findContours(matImg);

Bitmap bm = Bitmap.createBitmap(matResult.cols(), matResult.rows(), Bitmap.Config.ARGB_8888);

Utils.matToBitmap(matResult, bm);

imgView1.setImageBitmap(bm);

}

private Mat convertImageToMat(String resName) throws IOException {

int drawableResourceId = this.getResources().getIdentifier(resName, "drawable", getActivity().getPackageName());

Mat img = Utils.loadResource(getContext() , drawableResourceId , Imgcodecs.CV_LOAD_IMAGE_COLOR);

return img;

}

private Mat findContours (Mat image){

Mat kernel = Imgproc.getStructuringElement(Imgproc.MORPH_ELLIPSE, new Size(19,19));

Mat closed = new Mat(); // closed will have type CV_32F

Imgproc.morphologyEx(image, closed, Imgproc.MORPH_CLOSE, kernel);

Core.divide(image, closed, closed, 1, CvType.CV_32F);

Core.normalize(closed, image, 0, 255, Core.NORM_MINMAX, CvType.CV_8U);

Imgproc.threshold(image, image, -1, 255, Imgproc.THRESH_BINARY_INV

+ Imgproc.THRESH_OTSU);

return closed;

}

}

为了澄清按下相应的Button，调用“applyContoursFilter”方法，然后将图像从drawables(显示在imgView1中)转换为Mat对象。 之后调用“findContours”方法，然后Mat-object转换回bmp格式并再次设置为imgView1。

那应该是怎么回事。 但上面发布的nullpointer错误被抛出，我无法弄清楚它来自何处或如何解决它。

我是Android的新手，非常感谢你的帮助。