CODEWITHSUNDEEP
javaandroidandroid-asynctasktry-catch
Asimaruk
Asimaruk

Reputation: 145

Java: Try block stops before it's end without any exceptions

What makes me crazy is that my program stops in the middle of try block and continuous after all catch blocks! Here are details. I got AsyncTask

public class BigBitmapLoader extends AsyncTask<Uri, Void, Bitmap>
{

    public BigBitmapLoader(ScribblesView scribbles)
    {
        scribblesRef = new WeakReference<ScribblesView>(scribbles);
    }

    @Override
    protected Bitmap doInBackground(Uri... params)
    {
        InputStream is;
        try
        {
            ScribblesView scribs = scribblesRef.get();
            if (scribs != null)
            {
                is = scribs.getContext().getContentResolver().openInputStream(params[0]);
                Bitmap bitmap = BitmapFactory.decodeStream(is);
                is.close();
                return bitmap;
            }
        }
        catch(FileNotFoundException e)
        {
            Log.e(ERROR_TAG, e.toString());
        }
        catch(IOException e)
        {
            Log.e(ERROR_TAG, e.toString());
        }
        return null;
    }

    @Override
    protected void onPostExecute(Bitmap bitmap)
    {
        ScribblesView scribs = scribblesRef.get();
        if (scribs != null) scribs.setBigBitmap(bitmap);
    }

    private WeakReference<ScribblesView> scribblesRef;

    private static final String ERROR_TAG = "BigBitmapLoader";

}

In doInBackground() it comes to is.close() and then immediately jumps to return null after all catch blocks. Thus it skips return bitmap. At this point I got no exceptions. Only later when returned bitmap is used I got NPE. Any ideas?

Upvotes: 0

Views: 142

Answers (4)

Asimaruk
Asimaruk

Reputation: 145

The reason was that I had an exception on main thread. But there was no links on it in log. Here if (scribs != null) scribs.setBigBitmap(bitmap); in setBigBitmap() I used uninitialized variable. Fixed it and all works. But debuger still "jumps". Maybe some bugs in eclipse's debuger, because now it returns a returns a proper value. And did it before. It was only uninitialized variable. Thank you all for your answers)

Upvotes: 0

John Vint
John Vint

Reputation: 40256

It's failing because of a NullPointerException from is you just don't see it. When an exception occurs in an ExecutorService from a Callable or Runnable the exception is swallowed (unless a UncaughtExceptionHandler is set). Note AsyncTask uses (or at least last I checked) the ExecutorService for async execution.

doInBackground will run on another thread, if a RuntimeException occurs it will not print anywhere that isn't specified (ie swallow the exception).

I suggest you add a third catch block 

} catch(RuntimeException ex){
   ex.printStackTrace(); //or log
}

In short, the InputStream is probably null.

Upvotes: 2

dimoniy
dimoniy

Reputation: 5995

Well, the debugger's line numbers are sometimes off, so maybe that's the issue there. Do a clean build. Also, I would move is.close() to finally block. It's a good idea in general in order to make sure that you properly dispose the resources. So it would go something like this:

InputStream is = null;
try
    {
     // do stuff
} catch(FileNotFoundException e)
{
    Log.e(ERROR_TAG, e.toString());
} catch(IOException e) {
    Log.e(ERROR_TAG, e.toString());
} finally {
  if (is != null) {
     is.close();
  }
}

Upvotes: 2

Ankit Rustagi
Ankit Rustagi

Reputation: 5637

You see no exceptions because, no exceptions occured

        ScribblesView scribs = scribblesRef.get();
        if (scribs != null)
        {
            is = scribs.getContext().getContentResolver().openInputStream(params[0]);
            Bitmap bitmap = BitmapFactory.decodeStream(is);
            is.close();
            return bitmap;  // return statement
        }

The return statement maybe returns null. try debugging the method "decodeStream"

Upvotes: 1

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