Activity restart on rotation Android
In my Android application, when I rotate the device (slide out the keyboard) then my Activity
is restarted ( onCreate
is called). Now, this is probably how it's supposed to be, but I do a lot of initial setting up in the onCreate
method, so I need either:
onCreate
is not called again and the layout just adjusts or onCreate
is not called. Using the Application Class
Depending on what you're doing in your initialization you could consider creating a new class that extends Application
and moving your initialization code into an overridden onCreate
method within that class.
public class MyApplicationClass extends Application {
@Override
public void onCreate() {
super.onCreate();
// TODO Put your application initialization code here.
}
}
The onCreate
in the application class is only called when the entire application is created, so the Activity restarts on orientation or keyboard visibility changes won't trigger it.
It's good practice to expose the instance of this class as a singleton and exposing the application variables you're initializing using getters and setters.
NOTE: You'll need to specify the name of your new Application class in the manifest for it to be registered and used:
<application
android:name="com.you.yourapp.MyApplicationClass"
Reacting to Configuration Changes [UPDATE: this is deprecated since API 13; see the recommended alternative]
As a further alternative, you can have your application listen for events that would cause a restart – like orientation and keyboard visibility changes – and handle them within your Activity.
Start by adding the android:configChanges
node to your Activity's manifest node
android:configChanges="keyboardHidden|orientation"
or for Android 3.2 (API level 13) and newer:
android:configChanges="keyboardHidden|orientation|screenSize"
Then within the Activity override the onConfigurationChanged
method and call setContentView
to force the GUI layout to be re-done in the new orientation.
@Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
setContentView(R.layout.myLayout);
}
Update for Android 3.2 and higher:
Caution : Beginning with Android 3.2 (API level 13), the "screen size" also changes when the device switches between portrait and landscape orientation. Thus, if you want to prevent runtime restarts due to orientation change when developing for API level 13 or higher (as declared by the minSdkVersion and targetSdkVersion attributes), you must include the "screenSize"
value in addition to the "orientation"
value. That is, you must declare android:configChanges="orientation|screenSize"
. However, if your application targets API level 12 or lower, then your activity always handles this configuration change itself (this configuration change does not restart your activity, even when running on an Android 3.2 or higher device).
Instead of trying to stop the onCreate()
from being fired altogether, maybe try checking the Bundle
savedInstanceState
being passed into the event to see if it is null or not.
For instance, if I have some logic that should be run when the Activity
is truly created, not on every orientation change, I only run that logic in the onCreate()
only if the savedInstanceState
is null.
Otherwise, I still want the layout to redraw properly for the orientation.
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_game_list);
if(savedInstanceState == null){
setupCloudMessaging();
}
}
not sure if this is the ultimate answer, but it works for me.
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