Question

Here is a few bit of code:

public class ShowDialog extends Thread {
private static String mTitle="Please wait";
private static String mText="Loading...";
private Activity mActivity;
private ProgressDialog mDialog;

ShowDialog(Activity activity) {
    this(activity, mTitle, mText);
}
ShowDialog(Activity activity, String title) {
    this(activity, title, mText);
}
ShowDialog(Activity activity, String title, String text) {
    super();
    mText=text;
    mTitle=title;
    mActivity=activity;
    if (mDialog == null) {
        mDialog = new ProgressDialog(mActivity);
        mDialog.setTitle(mTitle);
        mDialog.setMessage(mText);
        mDialog.setIndeterminate(true);
        mDialog.setCancelable(true);
        mDialog.setOnCancelListener(
            new DialogInterface.OnCancelListener() {
                @Override
                public void onCancel(DialogInterface arg0) {
                    mDialog.dismiss();
                    interrupt();
                }
            });
    }
}

public void run() {
    mDialog.show();
    while(!isInterrupted())
    mDialog.dismiss();
    mDialog=null;
}

}

And in my main activity:

ShowDialog show = new ShowDialog(this, "Please wait!","Loading badly...");
    show.start();
    SystemClock.sleep(2000);
    show.interrupt();

I know I might use an async task and all the stuff but that is not what I want. Replace the SystemClock.sleep by anything that takes some time. The idea is to execute the code between start and interrupt in the UI thread and make a seperate thread handling the ProgressDialog.
What’s wrong with my thread ?

Thanks a lot!

Answer 1

To wait for a Thread to complete, you should use the Thread.join() method. But now I see you’re not wanting to wait for it to complete, but you need to control when it completes. Still, you want to avoid interrupting threads in this fashion.

In your ShowDialog class, add a dismiss() method that you can call from your main, instead of interrupt(). Also add a boolean dismiss = false instance variable. In dismiss(), add dismiss = true, then notify();. In run(), replace your constant while() loop (was running constantly, and very inefficient) with while(!dismiss){wait()}. You will still need to add synchronization blocks and exception handling, but this should get you off to a good start.

Here is a generic-Java (non-android) simplified example:

public static class ShowDialog extends Thread{

    protected boolean dismiss;

    public void dismiss(){
        dismiss = true;
        synchronized(this){
            notifyAll();
        }
    }

    @Override
    public void run(){
        System.out.println("Running...");
        // Show your dialog here.
        while(!dismiss){
            synchronized(this){
                try{
                    wait();
                }catch(InterruptedException ie){
                    ie.printStackTrace();
                }
            }
        }
        System.out.println("Quitting...");
        // Dismiss your dialog here.
    }

}

public static void main(String[] args) throws Exception{
    ShowDialog sd = new ShowDialog();
    sd.start();
    Thread.sleep(2000);
    sd.dismiss();
}

You mentioned you didn’t want to use AsyncTask, but I would still reconsider. (What are your reasons against it?)