How to display progress dialog before starting an activity in Android?

You should load data in an AsyncTask and update your interface when the data finishes loading.

You could even start a new activity in your AsyncTask's onPostExecute() method.

More specifically, you will need a new class that extends AsyncTask:

public class MyTask extends AsyncTask<Void, Void, Void> {
  public MyTask(ProgressDialog progress) {
    this.progress = progress;
  }

  public void onPreExecute() {
    progress.show();
  }

  public void doInBackground(Void... unused) {
    ... do your loading here ...
  }

  public void onPostExecute(Void unused) {
    progress.dismiss();
  }
}

Then in your activity you would do:

ProgressDialog progress = new ProgressDialog(this);
progress.setMessage("Loading...");
new MyTask(progress).execute();

When you start a long-running process on Android, its always advisable to do it on another thread. You can then use the UI thread to display a progress dialog. You cannot display a progress dialog in the same (UI) thread in which the process is running.

Do the following to start your process

pd = ProgressDialog.show(this, "Synchronizing data", "Please wait...");
Thread t = new Thread(this);
t.start();

For this your activity should implement Runnable as follows

public class SyncDataActivity extends Activity implements Runnable

And finally a method to perform the long-running process

@Override
public void run() {
      //your code here
}