Prevent android to start another instance of app

Question

I'm unable to make my app to run only one instance. When I press on the app to start it then press the home button and press on the app start another instance the previous instance is not being killed before starting a new one. When the app is loaded I press back button to close it and then another instance pops up right after closing the first one...

AndroidManifest.xml

<activity android:name=".StartUpActivity" android:configChanges="orientation|screenSize" android:label="@string/app_name" android:noHistory="true" android:launchMode="singleTask"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity>

StartUpActivity

@Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_loading); new Thread(new Runnable() { @Override public void run() { Intent activityIntent; // DO STUFF activityIntent = new Intent(context, RegNewUser.class); startActivity(activityIntent); } }).start(); }

"Prevent android to start another instance of app" -- there will only ever be one instance of your app. There may be more than one instance of an activity. An activity is not an app. — CommonsWare
– CommonsWare, Commented Aug 12, 2016 at 16:37

Lino · Accepted Answer · 2016-08-12 16:25:03Z

Do not create a new thread to start a new activity. This code must be executed in the UI thread.

@Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_loading); Intent activityIntent; activityIntent = new Intent(context, RegNewUser.class); startActivity(activityIntent); }

is it ok if i start a new activity inside OnPostExecute of AsyncTask?
it is clearly much better. However, I suggest to create a "communication channel" between your thread and the UI thread. You can for instance use an Handler developer.android.com/training/multiple-threads/…

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