Can not start new activity from alertdialog onclicklistener when activitygroup is used

Question

I simply have 2 tabs and used Experience - Multiple Android Activities in a TabActivity as reference.
My class Architecture is like this:
MainActivity extends TabActivity
1.TabGroup1Activity extends TabGroupActivity (TabGroupActivity-class implemented from above reference)
1.i. Tab1Activity extends MapActivity (which has multiple marker)
2.TabGroup2Activity extends TabGroupActivity
2.i. Tab2Activity

In second tab (Tab2Activity) i show the google map which has multiple markers. On Taping the marker I showed the alertdialog with More Info option.
Onclicking the More Info Option i have to start new activity without loosing tabs at bottom.

where is the error i dont know ??

MapItemizedOverlay.java

public class InformationItemizedOverlay extends ItemizedOverlay<OverlayItem> {
private ArrayList<OverlayItem> mOverlays = new ArrayList<OverlayItem>();
private Context mContext;
Activity parentContext;

public InformationItemizedOverlay(Drawable defaultMarker, Context context,
        Activity parent) {
    super(boundCenterBottom(defaultMarker));

    mContext = context;
    parentContext = parent;
}

public void addOverlay(OverlayItem overlay) {
    mOverlays.add(overlay);
    populate();
}

@Override
protected OverlayItem createItem(int i) {
    return mOverlays.get(i);
}

@Override
public int size() {
    return mOverlays.size();
}

@Override
protected boolean onTap(int index) {

    OverlayItem item = mOverlays.get(index);
    AlertDialog.Builder dialog = new AlertDialog.Builder(parentContext);
    dialog.setTitle(item.getTitle());
    dialog.setMessage(item.getSnippet());
    dialog.setPositiveButton("More Info..",
            new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    // TODO Auto-generated method stub
                    Intent test = new Intent(parentContext,
                            AboutActivity.class);
                    TabGroupActivity parentActivity = (TabGroupActivity) parentContext;
                    parentActivity
                            .startChildActivity("AboutActivity", test);
                }
            });
    dialog.show();
    return true;

}
}

When i try with above code, error gives when i click the More Info button at alertdialog.
When i remove the alertdialog and write the following code, it works fine, opens new activity in the same tab:

@Override
protected boolean onTap(int index) {

    OverlayItem item = mOverlays.get(index);

                    Intent test = new Intent(parentContext,
                            AboutActivity.class);
                    TabGroupActivity parentActivity = (TabGroupActivity) parentContext;
                    parentActivity
                            .startChildActivity("AboutActivity", test);
                }
            });

    return true;

}

How can i make it work to open new activity when i click the More Info button at alertdialog ??
Help !!

04-05 17:42:02.171: W/dalvikvm(2631): threadid=1: thread exiting with uncaught exception (group=0x4001d800) 04-05 17:42:02.171: E/AndroidRuntime(2631): FATAL EXCEPTION: main 04-05 17:42:02.171: E/AndroidRuntime(2631): java.lang.ClassCastException: com.bbs.MainActivity 04-05 17:42:02.171: E/AndroidRuntime(2631): at com.bbs1.InformationItemizedOverlay$1.onClick(InformationItemizedOverlay.java:63) 04-05 17:42:02.171: E/AndroidRuntime(2631): at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:158) 04-05 17:42:02.171: E/AndroidRuntime(2631): at android.os.Handler.dispatchMessage(Handler.java:99) 04-05 17:42:02.171: E/AndroidRuntime(2631): at android.os.Looper.loop(Looper.java:123) 04-05 17:42:02.171: E/AndroidRuntime(2631): at android.app.ActivityThread.main(ActivityThread.java:4627) 04-05 17:42:02.171: E/AndroidRuntime(2631): at java.lang.reflect.Method.invokeNative(Native Method) 04-05 17:42:02.171: E/AndroidRuntime(2631): at java.lang.reflect.Method.invoke(Method.java:521) 04-05 17:42:02.171: E/AndroidRuntime(2631): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) 04-05 17:42:02.171: E/AndroidRuntime(2631): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626) 04-05 17:42:02.171: E/AndroidRuntime(2631): at dalvik.system.NativeStart.main(Native Method)

Answer 1

You have to run the AlertDialogue on current UI Thread. Use runOnUiThread() to start the UI Thread.Here is the example:

runOnUiThread(new Runnable() {
 @Override
 public void run() {
  AlertDialog.Builder dialog = new AlertDialog.Builder(parentContext);
  dialog.setTitle(item.getTitle());
  dialog.setMessage(item.getSnippet());
  dialog.setPositiveButton("More Info..",new DialogInterface.OnClickListener() {
  @Override
  public void onClick(DialogInterface dialog, int which) {
  // TODO Auto-generated method stub
  Intent test = new Intent(parentContext,AboutActivity.class);
  TabGroupActivity parentActivity = (TabGroupActivity) parentContext;
  parentActivity.startChildActivity("AboutActivity", test);
  }
  });
  dialog.show();
 }//run
});//runOnUIThred