crash - When I close / click back button the google vision api qr code scanner app crashes

Question

When i click on the reader button opened up asking permission for camera, allowed after that when i click on close button or click on back button app itself quit. force quit.

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Thread$State

java.lang.Thread.getState()' on a null object reference

    at 

com.notbytes.barcode_reader.camera.CameraSource$FrameProcessingRunnable.release(CameraSource.java:1101)

    at com.notbytes.barcode_reader.camera.CameraSource.release(CameraSource.java:327)

    at com.notbytes.barcode_reader.camera.CameraSourcePreview.release(CameraSourcePreview.java:70)

    at com.notbytes.barcode_reader.BarcodeReaderFragment.onDestroy(BarcodeReaderFragment.java:367)

    at androidx.fragment.app.Fragment.performDestroy(Fragment.java:2927)

    at androidx.fragment.app.FragmentStateManager.destroy(FragmentStateManager.java:482)

    at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1294)

    at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1354)

    at androidx.fragment.app.FragmentManager.moveFragmentToExpectedState(FragmentManager.java:1432)

    at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1495)

    at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:2617)

    at androidx.fragment.app.FragmentManager.dispatchDestroy(FragmentManager.java:2601)

    at androidx.fragment.app.Fragment.performDestroy(Fragment.java:2922)

    at androidx.fragment.app.FragmentStateManager.destroy(FragmentStateManager.java:482)

    at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1294)

    at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1354)

    at androidx.fragment.app.FragmentManager.moveFragmentToExpectedState(FragmentManager.java:1432)

    at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1495)

    at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:2617)

    at androidx.fragment.app.FragmentManager.dispatchDestroy(FragmentManager.java:2601)

    at androidx.fragment.app.FragmentController.dispatchDestroy(FragmentController.java:330)

    at androidx.fragment.app.FragmentActivity.onDestroy(FragmentActivity.java:365)

    at androidx.appcompat.app.AppCompatActivity.onDestroy(AppCompatActivity.java:242)

    at android.app.Activity.performDestroy(Activity.java:8225)

    at android.app.Instrumentation.callActivityOnDestroy(Instrumentation.java:1342)

    at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:5441)

    at android.app.ActivityThread.handleDestroyActivity(ActivityThread.java:5493)?

    at android.app.servertransaction.DestroyActivityItem.execute(DestroyActivityItem.java:44)?

   

Camera source

Releases the underlying receiver. This is only safe to do after the associated thread

      has completed, which is managed in camera source's release method above.
     
    @SuppressLint("Assert") 

    void release() {

        assert (mProcessingThread.getState() == State.TERMINATED);

        mDetector.release();

        mDetector = null;

}

Camera source

Stops the camera and releases the resources of the camera and underlying detector.

public void release() {

    synchronized (mCameraLock) {

        stop();

        mFrameProcessor.release();

} }

camera source preview

public void release() {

    if (mCameraSource != null) {

        mCameraSource.release();

        mCameraSource = null;

    }
}

Barcode reader fragment

Releases the resources associated with the camera source, the associated detectors, and the

rest of the processing pipeline.

@Override
public void onDestroy() {

    super.onDestroy();

    if (mPreview != null) {

        mPreview.release();
    }
}

Answer 1

等待大神解答