I’ve been fooling around with the Android development platform. It’s quite an adjustment, coming from the iPhone world. I thought I’d post a simple equivalent to the SwingWorker class that works with Android’s Event Dispatch Thread. Here it is:

package ca.razorwire.util;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

import android.os.Handler;
import android.os.Looper;
import android.util.Log;

public abstract class UIWorker
{
  private static final ExecutorService __execSvc;
  private static final Handler __edtHandler;

  private static final String TAG = "UIWorker";

  static
  {
    __execSvc = Executors.newSingleThreadExecutor();
    __edtHandler = new Handler( Looper.getMainLooper() );
  }

  public abstract void doInBackground();

  public void done()
  {
    // Log.d(TAG, "done() executing in thread " + Thread.currentThread().getName() );
    // This space intentionally left blank
  }

  public void execute()
  {
    // Log.d(TAG, "execute() executing in thread " + Thread.currentThread().getName() );
    final Runnable doneRunner = new Runnable()
    {
      public void run()
      {
        UIWorker.this.done();
      }
    };

    final Runnable bgRunner = new Runnable()
    {
      public void run()
      {
        // Log.d(TAG, "bgRunner executing in thread " + Thread.currentThread().getName() );
        UIWorker.this.doInBackground();
        __edtHandler.post( doneRunner );
      }
    };
    __execSvc.submit(bgRunner);
  }
}

And here’s a sample usage:

      UIWorker worker = new UIWorker()
      {
        public void doInBackground()
        {
          Log.d( TAG, "Sleeping for a bit." );
          try { Thread.sleep( 10000 ); } catch ( Exception ignore ) {};
        }
      };
      Log.d( TAG, "Executing worker..." );
      worker.execute();
      Log.d( TAG, "Returned from execute()" );

If you uncomment the Log calls in UIWorker, you should see some output like this:

07-08 12:14:11.015: DEBUG/rweeks(1078): Executing worker...
07-08 12:14:11.015: DEBUG/UIWorker(1078): execute() executing in threadmain
07-08 12:14:11.025: DEBUG/UIWorker(1078): bgRunner executing in thread pool-1-thread-1
07-08 12:14:11.035: DEBUG/rweeks(1078): Sleeping for a bit.
07-08 12:14:11.035: DEBUG/rweeks(1078): Returned from execute()
07-08 12:14:21.038: DEBUG/UIWorker(1078): done() executing in thread main

Public domain code, no guarantees, seems to work.