How to set a theme to whole application in code, but not in the Manifest?

Question

I know how to set theme to whole application in manifest,but how to set theme to whole application programmatically ? I am trying this: getApplicationContext.se

Answer 1

I use a custom activity for all activities in my application.

Then I check a preference value in the onCreate of my inherited activity e.g.

public class MyCustomActivity extends Activity {

protected void onCreate(Bundle savedInstanceState) {
        SharedPreferences prefs = PreferenceManager
                .getDefaultSharedPreferences(this);
        if(prefs.getBoolean("use_light_theme",false)==true)
        {
            setTheme(R.style.AppThemeLight);
        }
        super.onCreate(savedInstanceState);

}

//styles.xml