How to come back to my parent-activity without losing data?

Question

I have an activity A with a "child activity" which is the activity B. When I create an activity, like in this case in android, I choose for activity B, that his parent shall be activity A.

So, when I start my application, I have an icon in the appbar in the activity B, where I can go to the activity A.

In my case, the user for example edit-text and manipulate some variables in the activity A and call activity B with Intent.

NOW, in activity B, when I click on the "back" icon, I will go back to the parent activity in this case activity A and all manipulated data are "away", because the screen will be relaunched.

But when I dont click on the icon in the activity B but instead click "back" on my mobile phone, I will come back to activity A and all manipulated data will be still there.

SO my question is, is there a way, to come back to activity A by clicking the back icon in activity B, without that the screen will be relaunched. Because this icon was automatically added, when I say, which activity have to be the parent class. I would like, that I can go back with this icon, but not relaunch the screen, instead continue, where I was "last" time.

I show you a part of my manifest file for the activity B:

<activity
            android:name=".strassenfuehrer_screen.VideoPlayerHandlungsleitfadenStrassenfuehrerActivity"
            android:label="Straßenführer  >  Handlungsleitfaden  >  VideoPlayer"
            android:parentActivityName=".strassenfuehrer_screen.MitHandlungsleitfadenStrassenfuehrerScreenActivity">
            <meta-data
                android:name="android.support.PARENT_ACTIVITY"
                android:value="de.derdoenerdon.ressourcencockpit.strassenfuehrer_screen.MitHandlungsleitfadenStrassenfuehrerScreenActivity" />
        </activity>

Here you can see the "back icon" in the activity B.

For help, I would be very thankfull, I am new in android and have difficulties with it.

Thanks a lot

Answer 1

In your manifest for Activity A add this attribute:

android:launchMode="singleTask"

This should solve your problem.

This makes sure that there is only one instance of Activity A in the BackStack. Therefore Activity A is only created once per Task.

Hope this helps.

for more information https://developer.android.com/guide/components/activities/tasks-and-back-stack

Answer 2

You can override onSaveInstanceState() into your Activity and save your data before leaving that Activity.

@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
    savedInstanceState.putInt("KEY1", Value1);
    savedInstanceState.putInt("KEY2", Value2);

    // Always call the superclass so it can save the view hierarchy state
    super.onSaveInstanceState(savedInstanceState);
}

On coming back to that Activity you can get the saved data as bundle into you onCreate() method.

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState); // Always call the superclass first
    if (savedInstanceState != null) {
        // Restore value of members from saved state
        int val1 = savedInstanceState.getInt("Key1");
        int val2 = savedInstanceState.getInt("Key2");
    } else {
        // This is the case when you are openning this Activity for the for the first time
    }
}