如何保存上次访问的活动并在开始时启动它

Question

I have the MainActivity which is welcome activity and some other ones.
Lets suppose Act1 , Act2 and Act3 .
I want the program automatically redirect from MainActivity directly to last visited activity on every app launch.
whether Act1 , Act2 or Act3
Well, I tried to do this jump from main activity to last visited activity , but it didn't work.
here's code what I've already tried and didn't work:

MainActivity:

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        loadLocale();
        setContentView(R.layout.activity_main);

        SharedPreferences prefs = getPreferences(Context.MODE_PRIVATE);
        int restoredLevel = prefs.getInt("level", 0);
        if (restoredLevel > 0) {
            Intent i = new Intent(getApplicationContext(), MainActivity.class);
            startActivity(i);
        }
    }

Act1:

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.Act1);

        SharedPreferences.Editor editor = getPreferences(Context.MODE_PRIVATE).edit();
        editor.putInt("level", 1);
        editor.apply();
    }

(I simply want to change launcher activity depending on last visited activity, if you know any better solution for my problem, I will be thankful)

Answer 1

When launched via icon on the home screen, Android will always start the activity with the android.intent.action.MAIN filter in your AndroidManifest.xml, unless the application is already running (in which case it will obviously restore the activity on top of the stack).

To achieve what you described you can simply store the last visible activity in SharedPreferences and have a Dispatcher activity that starts the last activity according to the preferences.

So in every activity you want to re-start automatically:

@Override
protected void onPause() {
super.onPause();

SharedPreferences prefs = getSharedPreferences("X", MODE_PRIVATE);
Editor editor = prefs.edit();
editor.putString("lastActivity", getClass().getName());
editor.commit();
}

And a Dispatcher activity similar to the following:

public class WelcomeActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    Class<?> activityClass;

    try {
        SharedPreferences prefs = getSharedPreferences("X", MODE_PRIVATE);
        activityClass = Class.forName(
            prefs.getString("lastActivity", Activity1.class.getName()));
    } catch(ClassNotFoundException ex) {
        activityClass = Activity1.class;
    }

    startActivity(new Intent(this, activityClass));
}
}

Remarks

-->You could create a base class for the onPause override. -->The Dispatcher activity obviously needs to be the android.intent.action.MAIN action.