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:
- Put all the initial setting up in another function so it's not all lost on device rotation or
- Make it so
onCreate
is not called again and the layout just adjusts or - Limit the app to just portrait so that
onCreate
is not called.
Best Answer
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 overriddenonCreate
method within that class.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:
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 nodeor for Android 3.2 (API level 13) and newer:
Then within the Activity override the
onConfigurationChanged
method and callsetContentView
to force the GUI layout to be re-done in the new orientation.