Android SplashScreen

The problem is most likely that you are running the splash screen (some sort of Dialog such as ProgressDialog I assume) in the same thread as all the work being done. This will keep the view of the splash screen from being updated, which can keep it from even getting displayed to the screen. You need to display the splash screen, kick off an instance of AsyncTask to go download all your data, then hide the splash screen once the task is complete.

So your Activity's onCreate() method would simply create a ProgressDialog and show it. Then create the AsyncTask and start it. I would make the AsyncTask an inner class of your main Activity, so it can store the data it has downloaded to some variable in your Activity and close the ProgressDialog in its onPostExecute() method.

Not sure how to elaborate anymore without just showing the code, so here it is:

public class MyActivity extends Activity {
    private ProgressDialog pd = null;
    private Object data = null;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        // Show the ProgressDialog on this thread
        this.pd = ProgressDialog.show(this, "Working..", "Downloading Data...", true, false);

        // Start a new thread that will download all the data
        new DownloadTask().execute("Any parameters my download task needs here");
    }

    private class DownloadTask extends AsyncTask<String, Void, Object> {
         protected Object doInBackground(String... args) {
             Log.i("MyApp", "Background thread starting");

             // This is where you would do all the work of downloading your data

             return "replace this with your data object";
         }

         protected void onPostExecute(Object result) {
             // Pass the result data back to the main activity
             MyActivity.this.data = result;

             if (MyActivity.this.pd != null) {
                 MyActivity.this.pd.dismiss();
             }
         }
    }    
}

Obviously there are some pieces you need to fill in there, but this code should run and give you a good starting point (forgive me if there is a code error, I don't have access to the Android SDK as I'm typing this currently).

Some more good reading on the subject of AsyncTasks in Android can be found here and here.

I know that this question is pretty old, and the OP may not need it anymore. But I just want to add this answer to help people who may need this to archive a splash screen.

Answer (only work on Android Oreo or greater versions)

Actually, in the newer version of Android (after Android Oreo), it already support built-in splash screen implement. That means you don't need to create extra activity to do that. You only need a drawable resource file for display.

Using this way is faster to your splash screen and soon show your content just after the initialization. But please note that this only work on Android Oreo or greater versions. On the previous version, it will show white instead of your splash screen (at least I think so).

You need this line in your AppTheme style:

<item name="android:windowSplashscreenContent">@drawable/YOUR_SPLASH_SCREEN_DRAWABLE</item>

This is a full example:

<!-- Base application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
    <!-- Customize your theme here. -->

    <!-- Set your splash screen here, it accept a resource from drawable directory-->
    <item name="android:windowSplashscreenContent" tools:targetApi="o">@drawable/splash_screen</item>
</style>

Reference

And for more informations about this attribute, see the official reference here: https://developer.android.com/reference/android/R.attr#windowSplashscreenContent

As it said, it is added in API level 26.

And a short extract of what it said:

Reference to a drawable to be used as the splash screen content of the window. This drawable will be placed on top of the windowBackground with its bounds inset by the system bars. If the drawable should not be inset by the system bars, use a fullscreen theme.

Note that even if no splashscreen content is set on the theme, the system may still show a splash screen using the other attributes on the theme, like the windowBackground.