Question

In my android application the scenario is this –

I have several images stored in the SD card.
Now in my app I have an Image view and I have to update this image view continuously
like a slide show is running. This has to be done by fetching images one by one from SD card and setting them in the same ImageView. Also the interval of image change in ImageView is fixed.
So I have a cursor which stores the information for fetching these images.
Now I am wondering what should be my approach for moving the cursor one by one and fetching images from SD card and setting them in my ImageView.

Should I use Timer Task and Timer or should I go with Handler or something else?

Please help as this is initial point of my app and I want to start in the right direction.

Answer 1

Since you’re retrieving large data from the SD card, it might be best to use a thread to retrieve/decode the bitmap.

In this case, a Timer would be useful because it runs on it’s own Java thread for scheduled periods of time. However, you have to keep in mind that you can’t update a UI element from a non-UI thread. Thus, you’d need a syncing element in place for when the bitmap is fully loaded to finally put the decoded bitmap in to the ImageView. In which case, you would need to use Handler anyway to send message queues to the UI thread.

Thus, I’d probably recommend using a combination of Handler and AsyncTask. Create an AsyncTask class that retrieves and decodes the bitmap in doInBackground(). Update the ImageView in onPostExecute(). Use a Handler to create and execute a new AsyncTask ever Nth milliesecond (whenever you update the view).

One advantage to this is it keeps all image retrieval in one class. You can open the cursor, retrieve, close it. This is safer than keeping a long-running cursor open.