Android: Uploading number of images causing Heap size to grow big - how to solve that?

I'm writing app where user can take bunch of pictures (up to 20) and upload to server. Images need to be uploaded all together.

Here is my logic:

1. Take each picture, display thumb on a screen and resize picture on SD to 800x600 with 90 quality
2. Create object, populate properties (images) as Base64 string
3. Serialize object using GSON
4. Upload string

While testing I was getting errors "Out of Memory" when I was processing images. I thought and this is where all StackOverflow complains is - that it's some bug with BitmapFactory. Yes, error mostly shows up while resizing image but it is NOT related to this operation.

While I take pictures and process them (resize, etc) - heap size stays below 7-8mb. It's just 2-3Mb more than my usual app state.

When I submit those images to server and GSON + Base64 encoder comes into play - than it "explodes" and I get this:

Well - as you see - after process completed Allocated memory get's down as expected but Heap Size stays. Now, when I take more pictures or do something with app - I start to get those out of memory errors.

Here is my code to upload JSON. Any suggestions on improving it or handling something like that? Maybe I can stream JSON into file and do http from file or something?

wh开发者_StackOverflow社区ile (!c.isAfterLast())
        {
            String data = c.getString(colObjectData);
            TrailerInspection trailerInspection = MyGsonWrapper.getMyGson().fromJson(data, TrailerInspection.class);

            //Load image data
            for (TrailerUnitInspection trailerUnitInspection : trailerInspection.UnitInspections)
            {
                for (FileContainer fileContainer : trailerUnitInspection.Images)
                {
                    fileContainer.dataFromFile(mContext);
                }
            }

            data = MyGsonWrapper.getMyGson().toJson(trailerInspection);

            MyHttpResponse response = processPOST("/trips/" + c.getString(colTripId) + "/trailerinspection", data);

            if (response.Code ==  HttpURLConnection.HTTP_OK)
            {
                processed.add(c.getString(colGId));
            }

            c.moveToNext();
        }
        c.close();

The problem is that you're creating and keeping whole string, which is prepared to sending, in internal memory.

String data = MyGsonWrapper.getMyGson().toJson(trailerInspection);

This string may be very large. You should stream your data in chunks to server.
I haven't used gson yet, but in docs I found something like JsonWriter. Take a look at this class.

UPDATE:

ContentProducer cp = new ContentProducer() {
    public void writeTo(OutputStream outstream) throws IOException {
        JsonWriter writer = new JsonWriter(new OutputStreamWriter(outstream, "UTF-8"));
        // write code here
        writer.flush();
    }
};
HttpEntity entity = new EntityTemplate(cp);
HttpPost httppost = new HttpPost("http://server.address");
httppost.setEntity(entity);