Android 2.2: ProgressDialog Freezing In Second Thread

Question

I have recently experimented with creating an easy way to open a ProgressDialog up in a second thread, so if the main thread freezes the dialog will keep working.

Here is the class: public class ProgressDialogThread extends Thread { public Looper ThreadLooper; public Handler mHandler;

public ProgressDialog ThreadDialog; public Context DialogContext; public String DialogTitle; public String DialogMessage;

public ProgressDialogThread(Context mContext, String mTitle, String mMessage)
 {
  DialogContext = mContext;
  DialogTitle = mTitle;
  DialogMessage = mMessage;
 }

 public void run()
 {
  Looper.prepare();
  ThreadLooper = Looper.myLooper();

  ThreadDialog = new ProgressDialog(DialogContext);
  ThreadDialog.setTitle(DialogTitle);
  ThreadDialog.setMessage(DialogMessage);
  ThreadDialog.show();

  mHandler = new Handler();

  Looper.loop();
 }

 public void Update(final String mTitle, final String mMessage)
 {
  while(mHandler == null)
   synchronized(this) {
    try { wait(10); } 
    catch (InterruptedException e) {
     Log.d("Exception(ProgressDialogThread.Update)", e.getMessage() == null ? "MISSING MESSAGE" : e.getMessage());
    }
   }

  mHandler.post(new Runnable(){
   @Override
   public void run() {
    ThreadDialog.setTitle(mTitle);
    ThreadDialog.setMessage(mMessage);
   }});
 }

 public void Dismiss() 
 {
  while(ThreadDialog == null || mHandler == null)
   synchronized(this) {
    try { wait(10); } 
    catch (InterruptedException e) {
     Log.d("Exception(ProgressDialogThread.Dismiss)", e.getMessage() == null ? "MISSING MESSAGE" : e.getMessage());
    }
   }

  mHandler.post(new Runnable(){
   @Override
   public void run() {
    ThreadDialog.dismiss();
   }});
 }

 public void Continue() 
 {
  while(ThreadLooper == null || mHandler == null)
   synchronized(this) {
    try { wait(10); } 
    catch (InterruptedException e) {
     Log.d("Exception(ProgressDialogThread.Continue)", e.getMessage() == null ? "MISSING MESSAGE" : e.getMessage());
    }
   }

  mHandler.post(new Runnable(){
   @Override
   public void run() {
    ThreadLooper.quit();
   }});
 }

However it sometimes work perfectly but other times the application simply freezes and crashes eventually.

Here is an example of use:

ProgressDialogThread thread = new ProgressDialogThread(this, "Loading", "Please wait...");
thread.start();
// Do Stuff
thread.Dismiss();
thread.Continue();

It generates a lot of warning and even some crashes sometimes:

eg. Handler: Sending message to dead thread....

and exceptions like ANR in ...... Reason: keyDispatchingTimedOut

Thanks for any help, Alex.

Answer 1

When wanting to do stuff in separate threads on Android, you should look at the AsyncTask class. You can read about it here: http://developer.android.com/resources/articles/painless-threading.html

Googling (or searching here on Stack Overflow) will also give you plenty of information on how to use it it the above link isn't sufficient :)