Run activity only once, then always run the main one

Question

As the title says, Scenario is: On first time using the app, Show Screen A. Once you are done with screen A, the button will lead to you Screen B. From now on and forever, t

Answer 1

Just declare your Activity A as a launcher Activity in your AndroidManifest.xml and inside your Activity A onCreate() you can simply do this

private SharedPreferences mSharedPreferences;
private Editor mEditor;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_a);

    mSharedPreferences = getSharedPreferences("yourPrefsFileName", Context.MODE_PRIVATE));
    mEditor = mSharedPreferences.edit();

    if (mSharedPreferences.getBoolean("isfirstTime", true)) {
        mEditor.putBoolean("isFirstTime",false);
        mEditor.apply();
    }else{
         startActivity(new Intent(this, ActivityB.class));
         overridePendingTransition(0, 0);
         finish();
      }
}