Implementing AsyncTask: An error occured while executing doInBackground() throws Runtime exception

Question

I am trying to implement AsyncTak to inform the user that a background operation is running when a photo is taken. The AyncTask is able to display the setMessage function but along the line the app crashes and it displays the following error

Caused by: android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.

This is the complete codebase of my AsyncTask

private class CheckTypesTask extends AsyncTask<Void, Void, Void>{
             ProgressDialog asyncDialog = new ProgressDialog(MainActivity.this);


             @Override
             protected void onPreExecute() {
                 //set message of the dialog
                 asyncDialog.setMessage("Loading");
                 //show dialog
                 asyncDialog.show();
                 super.onPreExecute();
             }

             @Override
             protected Void doInBackground(Void... arg0) {

                 //don't touch dialog here it'll break the application
                 //do some lengthy stuff like calling login webservice
                 onPhotoTaken();

                 return null;
             }

             @Override
             protected void onPostExecute(Void result) {
                 //hide the dialog
                 asyncDialog.dismiss();

                 super.onPostExecute(result);
             }

     }

Then I am calling the AsyncTask in onActivity result this way:

if (resultCode == -1) {

            //onPhotoTaken();
            (new MainActivity.CheckTypesTask()).execute();

        } else {
            Log.v(TAG, "User cancelled");
        }
    }

EDITTED: This is the onPhotoTaken code and it is defined in MainActivity class.

public void onPhotoTaken() {

        _taken = true;

        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inSampleSize = 4;

        Bitmap bitmap = BitmapFactory.decodeFile(_path, options);

        try {
            //ProgressDialog dialog = ProgressDialog.show(this, "Loading", "Please wait...", true);
            ExifInterface exif = new ExifInterface(_path);
            int exifOrientation = exif.getAttributeInt(
                    ExifInterface.TAG_ORIENTATION,
                    ExifInterface.ORIENTATION_NORMAL);

            Log.v(TAG, "Orient: " + exifOrientation);

            int rotate = 0;

            switch (exifOrientation) {
            case ExifInterface.ORIENTATION_ROTATE_90:
                rotate = 90;
                break;
            case ExifInterface.ORIENTATION_ROTATE_180:
                rotate = 180;
                break;
            case ExifInterface.ORIENTATION_ROTATE_270:
                rotate = 270;
                break;
            }

            Log.v(TAG, "Rotation: " + rotate);

            if (rotate != 0) {

                // Getting width & height of the given image.
                int w = bitmap.getWidth();
                int h = bitmap.getHeight();

                // Setting pre rotate
                Matrix mtx = new Matrix();
                mtx.preRotate(rotate);

                // Rotating Bitmap
                bitmap = Bitmap.createBitmap(bitmap, 0, 0, w, h, mtx, false);


            }

            // Convert to ARGB_8888, required by tess
            bitmap = bitmap.copy(Bitmap.Config.ARGB_8888, true);
            //dialog.dismiss();

        } catch (IOException e) {
            Log.e(TAG, "Couldn't correct orientation: " + e.toString());
        }

Please what could be wrong?

Answer 1

Try this code

This is your layout which contain an trigger for image capture and an imageview to display captured image :-

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fillViewport="true"
    android:orientation="vertical"
    tools:context="com.serveroverload.cube.ui.HomeActivity" >

    <ImageView
        android:id="@+id/preview"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_above="@+id/take_picture"
        android:layout_alignParentTop="true"
        android:layout_margin="5dp" />

    <ImageView
        android:id="@+id/take_picture"
        android:layout_width="50dp"
        android:layout_height="50dp"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:layout_gravity="center"
        android:layout_margin="10dp"
        android:background="@drawable/flat_selector"
        android:padding="5dp"
        android:scaleType="fitXY"
        android:src="@drawable/take_pic" />

</RelativeLayout>

This is your android manifest with required permisions

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.camtest"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.CAMERA" />
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="21" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.serveroverload.cube.ui.HomeActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

This is camera handler class to re-size and rotate images if required currently it will sample image to 1024x1280 for UI

public class CamerHandler {

    private CamerHandler() {

        getAllImages();
    }

    private static CamerHandler camerHandler;

    public static CamerHandler GetCamerHandlerInstance() {
        if (null == camerHandler) {
            camerHandler = new CamerHandler();
        }
        return camerHandler;
    }

    private static final String CAM_DIRECTORY = "CamDirectory";
    private static final int MAX_HEIGHT = 1024;
    private static final int MAX_WIDTH = 1280;

    private ArrayList<File> imageURL = new ArrayList<File>();

    public ArrayList<File> getImageURL() {
        return imageURL;
    }

    public void setImageURL(ArrayList<File> imageURL) {
        this.imageURL = imageURL;
    }

    public void getAllImages() {

        imageURL.clear();

        File folder = new File(getImageDirectory());
        File[] listOfFiles = folder.listFiles();

        if (null != listOfFiles && listOfFiles.length != 0) {

            for (int i = 0; i < listOfFiles.length; i++) {
                if (listOfFiles[i].isFile()) {

                    imageURL.add(listOfFiles[i]);

                    System.out.println("File " + listOfFiles[i].getName());
                } else if (listOfFiles[i].isDirectory()) {
                    System.out.println("Directory " + listOfFiles[i].getName());
                }
            }
        }
    }

    /**
     * This method is responsible for solving the rotation issue if exist. Also
     * scale the images to 1024x1024 resolution
     *
     * @param context
     *            The current context
     * @param selectedImage
     *            The Image URI
     * @return Bitmap image results
     * @throws IOException
     */
    public Bitmap handleSamplingAndRotationBitmap(Context context, Uri selectedImage) throws IOException {

        // First decode with inJustDecodeBounds=true to check dimensions
        final BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;

        InputStream imageStream = context.getContentResolver().openInputStream(selectedImage);
        BitmapFactory.decodeStream(imageStream, null, options);
        imageStream.close();

        // Calculate inSampleSize
        options.inSampleSize = calculateInSampleSize(options, MAX_WIDTH, MAX_HEIGHT);

        // Decode bitmap with inSampleSize set
        options.inJustDecodeBounds = false;
        imageStream = context.getContentResolver().openInputStream(selectedImage);
        Bitmap img = BitmapFactory.decodeStream(imageStream, null, options);

        // img = rotateImageIfRequired(img, selectedImage);

        img = rotateBitmap(context, img, selectedImage);
        return img;
    }

    public Bitmap rotateBitmap(Context context, Bitmap bitmap, Uri selectedImage) {

        ExifInterface exif;
        try {
            exif = new ExifInterface(selectedImage.getPath());

            int orientation = exif.getAttributeInt(ExifInterface.TAG_ORIENTATION, ExifInterface.ORIENTATION_UNDEFINED);

            Matrix matrix = new Matrix();
            switch (orientation) {
            case ExifInterface.ORIENTATION_NORMAL:
                return bitmap;
            case ExifInterface.ORIENTATION_FLIP_HORIZONTAL:
                matrix.setScale(-1, 1);
                break;
            case ExifInterface.ORIENTATION_ROTATE_180:
                matrix.setRotate(180);
                break;
            case ExifInterface.ORIENTATION_FLIP_VERTICAL:
                matrix.setRotate(180);
                matrix.postScale(-1, 1);
                break;
            case ExifInterface.ORIENTATION_TRANSPOSE:
                matrix.setRotate(90);
                matrix.postScale(-1, 1);
                break;
            case ExifInterface.ORIENTATION_ROTATE_90:
                matrix.setRotate(90);
                break;
            case ExifInterface.ORIENTATION_TRANSVERSE:
                matrix.setRotate(-90);
                matrix.postScale(-1, 1);
                break;
            case ExifInterface.ORIENTATION_ROTATE_270:
                matrix.setRotate(-90);
                break;
            default:
                return bitmap;
            }
            // try {
            Bitmap bmRotated = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, true);
            bitmap.recycle();
            return bmRotated;

        } catch (IOException e) {

            e.printStackTrace();

            return null;
        } catch (OutOfMemoryError e) {
            e.printStackTrace();
            return null;
        }
    }

    /**
     * Calculate an inSampleSize for use in a {@link BitmapFactory.Options}
     * object when decoding bitmaps using the decode* methods from
     * {@link BitmapFactory}. This implementation calculates the closest
     * inSampleSize that will result in the final decoded bitmap having a width
     * and height equal to or larger than the requested width and height. This
     * implementation does not ensure a power of 2 is returned for inSampleSize
     * which can be faster when decoding but results in a larger bitmap which
     * isn't as useful for caching purposes.
     *
     * @param options
     *            An options object with out* params already populated (run
     *            through a decode* method with inJustDecodeBounds==true
     * @param reqWidth
     *            The requested width of the resulting bitmap
     * @param reqHeight
     *            The requested height of the resulting bitmap
     * @return The value to be used for inSampleSize
     */
    private int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
        // Raw height and width of image
        final int height = options.outHeight;
        final int width = options.outWidth;
        int inSampleSize = 1;

        if (height > reqHeight || width > reqWidth) {

            // Calculate ratios of height and width to requested height and
            // width
            final int heightRatio = Math.round((float) height / (float) reqHeight);
            final int widthRatio = Math.round((float) width / (float) reqWidth);

            // Choose the smallest ratio as inSampleSize value, this will
            // guarantee a final image
            // with both dimensions larger than or equal to the requested height
            // and width.
            inSampleSize = heightRatio < widthRatio ? heightRatio : widthRatio;

            // This offers some additional logic in case the image has a strange
            // aspect ratio. For example, a panorama may have a much larger
            // width than height. In these cases the total pixels might still
            // end up being too large to fit comfortably in memory, so we should
            // be more aggressive with sample down the image (=larger
            // inSampleSize).

            final float totalPixels = width * height;

            // Anything more than 2x the requested pixels we'll sample down
            // further
            final float totalReqPixelsCap = reqWidth * reqHeight * 2;

            while (totalPixels / (inSampleSize * inSampleSize) > totalReqPixelsCap) {
                inSampleSize++;
            }
        }
        return inSampleSize;
    }

    public void openGallery(Context context) {
        Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse("content://media/internal/images/media"));
        intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        context.startActivity(intent);
    }

    private void convertToBase64(Bitmap bitmap) {
        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        bitmap.compress(CompressFormat.JPEG, 30, byteArrayOutputStream);
        byte[] byteArray = byteArrayOutputStream.toByteArray();
        String encoded = Base64.encodeToString(byteArray, Base64.NO_WRAP);

        // bitmap.recycle();

        encoded = null;
        byteArray = null;
    }

    public String getImageDirectory() {

        return createDirIfNotExists().getAbsolutePath();
    }

    public File createDirIfNotExists() {

        File imageDirectory = new File(Environment.getExternalStorageDirectory(), CAM_DIRECTORY);
        if (!imageDirectory.exists()) {

            if (!imageDirectory.mkdirs()) {

                Log.e("imageDirectory:: ", "Problem creating Image folder");
            }
        }
        return imageDirectory;
    }
}

and this is activity code which take pictures and perform all down sampling and image rotation in background before updating on UI

public class HomeActivity extends Activity {

    static final int REQUEST_IMAGE_CAPTURE = 1;
    private ImageView previewLayout;
    private static final String TAG = "MainActivity";

    static Uri capturedImageUri = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home);

        // Imageview to display Image
        previewLayout = (ImageView) findViewById(R.id.preview);

        findViewById(R.id.take_picture).setOnClickListener(
                new OnClickListener() {

                    @Override
                    public void onClick(View v) {
                        dispatchTakePictureIntent();

                    }
                });

    }

    private void dispatchTakePictureIntent() {

        Intent intent = new Intent("android.media.action.IMAGE_CAPTURE");

        if (intent.resolveActivity(getPackageManager()) != null) {

            Calendar cal = Calendar.getInstance();

            // store image in new File in image directory
            File file = new File(CamerHandler.GetCamerHandlerInstance()
                    .getImageDirectory(), (cal.getTimeInMillis() + ".png"));

            if (!file.exists()) {
                try {
                    file.createNewFile();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                    Toast.makeText(getApplicationContext(),
                            "Failed to make file", 500).show();
                }
            } else {
                file.delete();
                try {
                    file.createNewFile();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                    Toast.makeText(getApplicationContext(),
                            "Failed to make file", 500).show();
                }
            }

            capturedImageUri = Uri.fromFile(file);
            intent.putExtra(MediaStore.EXTRA_OUTPUT, capturedImageUri);
            startActivityForResult(intent, REQUEST_IMAGE_CAPTURE);
        }

    }

    @SuppressLint("NewApi")
    @Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if (resultCode == RESULT_OK && requestCode == REQUEST_IMAGE_CAPTURE) {

            // update file in gallery
            sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE,
                    capturedImageUri));

            // Downsample image before displaying in imageview to avoi OOM
            // exception
            new LoadBitMap(previewLayout, HomeActivity.this)
                    .execute(capturedImageUri);

        } else {
            Log.e(TAG, "FAILED TO TAKE IMAGE");
        }
    }

}

class LoadBitMap extends AsyncTask<Uri, Void, Void> {

    public LoadBitMap(ImageView preview, Context context) {
        this.prevImageView = preview;
        this.mContext = context;
    }

    private Bitmap bitmap = null;
    private ImageView prevImageView;
    private Context mContext;

    @Override
    protected Void doInBackground(Uri... params) {
        try {

            bitmap = CamerHandler.GetCamerHandlerInstance()
                    .handleSamplingAndRotationBitmap(mContext, params[0]);

        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null;
    }

    @Override
    protected void onPostExecute(Void result) {
        if (null != bitmap) {

    prevImageView.setBackground(new BitmapDrawable(mContext
                    .getResources(), bitmap));
        }
        super.onPostExecute(result);
    }
}

Points to note here you can use Picasso or Glide for image loading task as we already have uri path in captureuri variable.

Answer 2

You are trying to access UI components (View) from a background thread in your case inside the doInBackground() method. You are not allowed to do that.

Call your function from onPostExecute()