Logout when closing app

Question

Guys, I have an app that runs login, for this I use sharedPreferences(), I have a quit button that causes the user to depress the system, which works this way:

SharedPreferences pref = getSharedPreferences("info",MODE_PRIVATE);
SharedPreferences.Editor editor = pref.edit();
editor.clear();
editor.commit();
Log.d("ESTADO_APP", "Deslogado");
finish();  

And it works perfectly, I would like when I close the App it will deploy, but not when minimize and leave open in the background, only when it is actually finalized.

Answer 1

I had recommended that you could use the method onDestroy, which is called when the system needs memory or when the Finish() method is called. But this might not work in some cases. So, the best thing to do is: you don’t need to wipe the data when the user leaves the app, but when they log in.

For this, we make a SplashActivity or a class Application. You can choose any one.

Splahactivity

We will not use any layout in our Splashactivity because it is not necessary. We don’t want the user to waste much time on it, it will be something fast, we will only show the app icon and ready.

<style name="AppTheme.Splash" parent="Theme.AppCompat.Light.NoActionBar">
    <item name="colorPrimary">@color/colorPrimary</item>
    <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
    <item name="colorAccent">@color/colorAccent</item>
    <item name="android:windowBackground">@mipmap/ic_launcher</item>
</style>

In this style tag, focus on the attribute windowBackground, because he is the one who will position the icon of our app on Splashscreen. You can exchange for a Drawable as well, if you want to make a custom image or leave without any background image.

Don’t forget to define this class on Manifest like the Entrypoint of the application.

public class SplashActivity extends AppCompatActivity {

    @Override
    public void onCreate(Bundle cycle) {
        super.onCreate(cycle);
        clearData();
        startActivity(new Intent(this, MainActivity.class));
        finish();
    }

    private void clearData() {
        SharedPreferences pref = getSharedPreferences("info",MODE_PRIVATE);
        SharedPreferences.Editor editor = pref.edit();
        editor.clear();
        editor.commit();
    }
}


<activity
        android:name="br.com.exemplo.SplashActivity" <!-- muda para o endereço correto -->
        android:theme="@style/AppTheme.Splash">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

Application

You will only need to create a class you inherit from Application and then clear the data.

public class MyApp extends Application {

    @Override
    public void onCreate() {
       clearData();
       startActivity(new Intent(this, MainActivity.class));
       finish();
    }

    private void clearData() {
        SharedPreferences pref = getSharedPreferences("info",MODE_PRIVATE);
        SharedPreferences.Editor editor = pref.edit();
        editor.clear();
        editor.commit();
    }
}

Don’t forget to point out in the Manifest in the Application tag the name for your Myapp class.

<Application
 .....
    android:name=".package.MyApp" />

As it was said, in the onDestroy method it gets kind of bad to put because it is not always called.