Sending Activity to background without finishing

Question

How can I make an activity go to background without calling its finish() method and return to the Parent activity that started this? I tried so much but I could not find a solution. So if you guys could help I would be very thankful.

Answer 1

The following will work if the Activity is running in a different task to its parent. To achieve this, see http://developer.android.com/guide/topics/manifest/activity-element.html#lmode.

public void onBackPressed () {
    moveTaskToBack (true);
}

The current task will be hidden, but its state will remain untouched, and when it is reactivated it will appear just as it was when you left it.

Answer 2

If you have data you want to cache / store / process in the background, you can use an AsyncTask or a Thread.

When you are ready to cache / transition to parent, you would do something like the following in one of your child Activity methods (assuming you started child with startActivityForResult() )

Thread Approach:

Thread t1 = new Thread(new Runnable() {

        @Override
        public void run() {
            // PUT YOUR CACHING CODE HERE

        }
});

t1.start();

setResult( whatever );
finish();

You can also use a Handler if you need to communicate anything back from your new thread.

AsyncTask Approach:

new CacheDataTask().execute( data params );
set_result( whatever );
finish();

The AsyncTask is for situations in which you need to process something in a new thread, but be able to communicate back with the UI process.