saving downloaded file to internal storage java/android fails

Question

I have an app who has to download some generated images (PNG).

I tried the standard approach ImageDownloader extends AsyncTask, doInBackground() retrieves the image and the onPostExecute() will try to save it to internal image.

(Part of the) code is below:

public class HandleImages extends AppCompatActivity {
String filename = "";

public boolean saveImageToInternalStorage(Bitmap image) {
    try {
        FileOutputStream fos = openFileOutput(filename, Context.MODE_PRIVATE);

        image.compress(Bitmap.CompressFormat.PNG, 100, fos);
        fos.close();

        return true;
    } catch (Exception e) {
        e.printStackTrace();
        return false;
    }
}

public Bitmap retrieveImage(String url){
    ImageDownloader task = new ImageDownloader();
    Bitmap image =  Bitmap.createBitmap(1, 1, Bitmap.Config.ARGB_8888);

    try {
        image = task.execute(url).get();
    } catch (InterruptedException e) {
        MainActivity.debb("InterruptedException - " + e.getMessage() + " in " + new Object(){}.getClass().getEnclosingMethod().getName());
        e.printStackTrace();
    } catch (ExecutionException e) {
        MainActivity.debb("ExecutionException - " + e.getMessage() + " in " + new Object(){}.getClass().getEnclosingMethod().getName());
        e.printStackTrace();
    }
    return image;
}


public class ImageDownloader extends AsyncTask<String, Void, Bitmap> {
    @Override
    protected Bitmap doInBackground(String... urls) {
        try {
            String[] filenames = urls[0].split("/");
            filename = filenames[filenames.length-1] + ".jpg";

            URL url = new URL(urls[0]);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();

            connection.connect();
            InputStream inputStream = connection.getInputStream();

            return BitmapFactory.decodeStream(inputStream);

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

    @Override
    protected void onPostExecute(Bitmap bitmap) {
        super.onPostExecute(bitmap);
        if (bitmap != null)
            saveImageToInternalStorage(bitmap);
    }
}
}

and the error that I get is: java.lang.NullPointerException: Attempt to invoke virtual method 'java.io.FileOutputStream android.content.Context.openFileOutput(java.lang.String, int)' on a null object reference.

It seems that the FileOutputStream fos = openFileOutput(..) fails, but have no idea why.

Also tried to prepend a path (sdCard.getPath() + "/" +) to the filename. As expected it did not make any difference.

Images are ok, I can see them in the browser. Also tried with uploaded images - instead of the generated ones, same result.

This is pretty odd, does anyone have any idea?

Thanks!

score 0 · Answer 1 · answered Feb 22 '17 at 10:15

private String saveToInternalStorage(Bitmap bitmapImage){
        ContextWrapper cw = new ContextWrapper(getApplicationContext());
         // path to /data/data/yourapp/app_data/imageDir
        File directory = cw.getDir("imageDir", Context.MODE_PRIVATE);
        // Create imageDir
        File mypath=new File(directory,"profile.jpg");

        FileOutputStream fos = null;
        try {           
            fos = new FileOutputStream(mypath);
       // Use the compress method on the BitMap object to write image to the OutputStream
            bitmapImage.compress(Bitmap.CompressFormat.PNG, 100, fos);
        } catch (Exception e) {
              e.printStackTrace();
        } finally {
            try {
              fos.close();
            } catch (IOException e) {
              e.printStackTrace();
            }
        } 
        return directory.getAbsolutePath();
    }

Hope this function helps you. If this doesn't help feel free to ask

saving downloaded file to internal storage java/android fails

1 Answers1