How to run a piece of code every open App?

//in onCreate
btnOK.setOnClickListener(new View.OnClickListener(){
			@Override
			public void onClick(View v){
                         
     Action();//***run this function only once whenever push btnOK ,and when open app again run only once too
    
     Action2();//run normally 

}});

//----Outside
public void Action(){
   //action....
}
public void Action2(){
   //action....
}

SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this);
if(!prefs.getBoolean("firstTime", false)) {
    // run your one time code
    SharedPreferences.Editor editor = prefs.edit();
    editor.putBoolean("firstTime", true);
    editor.commit();
}