How to show a ProgressDialog while changing from a activity to another activity?

i want to show a PD when my activity A starts another activity B. But in that onclick method, my A activity haves to do some work before start B, and B also haves to do some work because it haves to load a lot of data for the UI.

I need a PD that is viewed by the user in all the process of the loading data of changin from activity A to B.

¿how can do it?

i tryed storing a static ProgressDialog on MyApplication.java, and with these methods:

public static void showProgressDialog(Context c) {
    pd = ProgressDialog.show(c, c.getResources().getString(R.string.app_name), 
        c.getResources().getString(R.string.loading), true, false);    
}
public static void dism开发者_如何学PythonissProgressDialog(){
    pd.dismiss();
}

but it doesn't works, it doesn't shows nothing, i dont know why

how to achieve this by a easy way? i know that i can do it with async task, but that is too hard for me, i can't understand the code examples i am finding on this web and google

code examples are welcome

thanks

well, i agree with @Falmarri comment, the easy way is implementing that with an AsyncTask. Because AsyncTask manages the UIThread and a background thread.

i always do this with AsyncTask but i don´t think that paste here my code will help you, because your requirements maybe are not like mine, but i think you can do in this way;

Subclass the AsyncTask and override these methods;

• onPreExecute()... because this method is invoked in the ui thread you can create and show the progress dialog.

• doInBackground(Runnable task)... this method run in a background thread so you don´t have to worry about Threads handling... all you have to do is the hard work
  (process data, download data, etc)
  and publish any update to the ui that you want.

• onProgressUpdate(Object... values)... this method also is called in the ui thread, so you can update your
  progress dialog with the progress
  values.

• onPostExecute(Object result)... this method run in the ui thread so, you can show the operation
  result and dismiss the progress
  dialog, and invoke your new activity.

you can do all operations here, the activity A operation and activity B operation, and the AsynTask will manage for you the Threading management :)

Edit 1:

i don't know how much complex is your desing but here i make a project example, maybe it's not what you want but it has all stuff decribed here, in my answer, maybe like an example works.

i suggest that you read more about this class because is one of the most important, here you can read more about this mechanism... http://android-developers.blogspot.com/2009/05/painless-threading.html

You can add a prograss bar to your layout:

<FrameLayout
    android:id="@+id/mapLayout"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" >
        //your layout
    </LinearLayout>

    <ProgressBar
        android:id="@+id/progressBar"
        style="?android:attr/progressBarStyleLarge"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center" >
    </ProgressBar>

</FrameLayout>

Load the progress bar in your activity onCreate:

public void onCreate(final Bundle savedInstanceState) {

    mProgress = (ProgressBar) findViewById(R.id.progressBar);
    mProgress.setVisibility(View.VISIBLE);

    //rest your code       
}

Stop the progress bar when your activity starts:

@Override
protected void onStart() {

    //your code
    mProgress.setVisibility(View.GONE);        
    super.onStart();
}

1. Create a singleton instance for all the way loading/progress-dialog.
2. Use ApplicationContext for ProgressViews/dialogs
3. Manage From static functions accesible troughout app

These can be 3 ways to do so.