LogCat error in android studio which crashes app when running

Question

In this fragment I'm adding ZXingscanner view, and code shows no errors at all, but when I run app it crashes and stops every time.This app has 3 tabs with Fragment in each, and the fragment of one of the tabs is this scanner, but this view ruins the app for some reason. Here's the code of my fragment class:

import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.os.Vibrator;
import android.support.annotation.NonNull;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;

import com.google.zxing.BarcodeFormat;
import com.google.zxing.Result;
import com.hist_area.imeda.histarea.R;

import java.util.ArrayList;
import java.util.List;

import me.dm7.barcodescanner.zxing.ZXingScannerView;


public class EmptyFragment extends Fragment implements ZXingScannerView.ResultHandler {
    public static EmptyFragment create() {
        return new EmptyFragment();
    }
    Vibrator vibrator;


    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        }

        private ZXingScannerView mScannerView;
        private LinearLayout qrCameraLayout;

        @Override
        public View onCreateView (LayoutInflater inflater, ViewGroup container, Bundle
        savedInstanceState)
        {
            View v = inflater.inflate(R.layout.fragment_camera, container, false);

            qrCameraLayout = (LinearLayout) v.findViewById(R.id.camera_preview);
            mScannerView = new ZXingScannerView(getActivity().getApplicationContext());
            mScannerView.setLayoutParams(new LinearLayout.LayoutParams(
                    LinearLayout.LayoutParams.MATCH_PARENT,
                    LinearLayout.LayoutParams.MATCH_PARENT));
            qrCameraLayout.addView(mScannerView);

            List<BarcodeFormat> formats = new ArrayList<>();
            formats.add(BarcodeFormat.QR_CODE);
            mScannerView.setFormats(formats);

            return v;
        }

        @Override
        public void onResume ()
        {
            super.onResume();
            mScannerView.setResultHandler(this); // Register ourselves as a handler for scan results.
            mScannerView.startCamera();          // Start camera on resume
        }

        @Override
        public void onPause ()
        {
            super.onPause();
            mScannerView.stopCamera();
        }

        @Override
        public void handleResult ( final Result result)
        {
            vibrator.vibrate(369);
            Log.e("handleresult", result.getText());
            //Hold result
            AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
            builder.setTitle("             Scan Result");
            builder.setPositiveButton("Scan Again", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    mScannerView.resumeCameraPreview(EmptyFragment.this);
                }
            });
            builder.setNeutralButton("Main Page", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    mScannerView.stopCamera();
                    MainPageFragment.create();
                }


            });

            builder.setMessage(result.getText());
            AlertDialog alertDialog = builder.create();
            alertDialog.show();
        }


}

And here's code to XML LinearLayout which has this view in it :

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">


    <View
        android:id="@+id/camera_scanner"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout> 

Here's the LogCat error:

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.LinearLayout.addView(android.view.View)' on a null object reference
                                                                                at com.hist_area.imeda.histarea.fragment.EmptyFragment.onCreateView(EmptyFragment.java:52)
                                                                                at android.support.v4.app.Fragment.performCreateView(Fragment.java:2239)
                                                                                at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1332)
                                                                                at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1574)
                                                                                at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1641)
                                                                                at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:794)
                                                                                at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2415)
                                                                                at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2200)
                                                                                at android.support.v4.app.FragmentManagerImpl.optimizeAndExecuteOps(FragmentManager.java:2153)
                                                                                at android.support.v4.app.FragmentManagerImpl.execSingleAction(FragmentManager.java:2034)
                                                                                at android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:651)
                                                                                at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:143)
                                                                                at android.support.v4.view.ViewPager.populate(ViewPager.java:1239)
                                                                                at android.support.v4.view.ViewPager.populate(ViewPager.java:1087)
                                                                                at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1613)
                                                                                at android.view.View.measure(View.java:18788)
                                                                                at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:715)
                                                                                at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:461)
                                                                                at android.view.View.measure(View.java:18788)
                                                                                at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
                                                                                at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
                                                                                at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:139)
                                                                                at android.view.View.measure(View.java:18788)
                                                                                at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
                                                                                at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465)
                                                                                at android.widget.LinearLayout.measureVertical(LinearLayout.java:748)
                                                                                at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
                                                                                at android.view.View.measure(View.java:18788)
                                                                                at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
                                                                                at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
                                                                                at android.view.View.measure(View.java:18788)
                                                                                at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
                                                                                at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465)
                                                                                at android.widget.LinearLayout.measureVertical(LinearLayout.java:748)
                                                                                at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
                                                                                at android.view.View.measure(View.java:18788)
                                                                                at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
                                                                                at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
                                                                                at com.android.internal.policy.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2643)
                                                                                at android.view.View.measure(View.java:18788)
                                                                                at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2100)
                                                                                at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1216)
                                                                                at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1452)
                                                                                at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1107)
                                                                                at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6013)
                                                                                at android.view.Choreographer$CallbackRecord.run(Choreographer.java:858)
                                                                                at android.view.Choreographer.doCallbacks(Choreographer.java:670)
                                                                                at android.view.Choreographer.doFrame(Choreographer.java:606)
                                                                                at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:844)
                                                                                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 co
08-04 17:29:54.075 4819-4819/com.hist_area.imeda.histarea I/Process: Sending signal. PID: 4819 SIG: 9

Answer 1

You have not provided an id to this element in your layout file. Do this:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/camera_preview" <!-- This was missing -->
>
 <View
    android:id="@+id/camera_scanner"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />
 </LinearLayout>