Question

I’m really confused about this, but when I’m trigging a thread from my SurfaceView, im sending a Handler with the constructor like this

private static Thread thread;

public SurfaceView(Context localContext) {
      //other stuff
      thread = new Thread(mySurfaceHolder, myEngine, this, new Handler());
      //other stuff
}

and in my thread-class I assign a Handler-object with the handler I sent from my view, like this:

    public Thread (SurfaceHolder lHolder,
    Engine lEngine,
    View lView,
    Handler lHandler){

    surfaceHolder = lHolder;
    engine = lEngine;
    view = lView;
    handler = lHandler;

}

So what does this Handler do? I never use it in my thread-class in any ways, so why are the examples on the web still showing me that I should send a handler with the constructor?
I can’t see the connection.

Answer 1

I assume in your code you are extending Thread, because there is no constructor taking a handler for the Thread class. The handler is used to communicate back to the UI thread, as the Android threading model requires UI operations to be performed on a special dedicated thread.

When creating a new thread, the code is executed in a background thread, and thus UI-operations are unsafe. If you do not need to do anything UI-related, you can remove the handler.

Since Android API 3, there is AsyncTask, which makes communication between background and UI easier and alleviates the need to use a handler.

Examples:

• For an example of using a Handler,
  see this.
• See Painless
  Threading as well, which contains links to sample projects using threading.