What Android event is only called once until the activity is destroyed?

Question

I'm looking for a single answer (but I might be asking the wrong question)

Question- does any event only get called once TOTAL until an activity is destroyed?

I ask because when my user rotates the phone to landscape oncreate and onstart are both invoked causing a reload of sorts.

I'm looking for an event that I could put behavior into that would only get run 1x (until the activity is killed)

Thank you in advance

Answer 1

If it is specific to the Activity just check your savedInstanceState parameter in the onCreate event. If it is null, run your code, if not, your code has already been run.

Example:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    if(savedInstanceState == null) {
        // Run your code
    }        
}

savedInstanceState will always be null when onCreate is run for the first time, and it will be populated thereafter.

Answer 2

You don't really specify what you're trying to do with it, so I can't guarantee this is appropriate for your use, but Application.onCreate is only called once.

Answer 3

If you want to eliminate the recreation of your activity on an orientationchange you can listen for configchanges in the manifest.

    <activity
            android:name=".MyActivity"
            android:configChanges="orientation" >
    </activity>

And then you can override onConfigurationChanged like so:

@Override
public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged( newConfig );

    LinearLayout main = (LinearLayout) findViewById( R.id.mainLayout );
    main.requestLayout();
}

to recreate the layout so that it matches the new orientation, without recreating the entire activity.

Answer 4

Check http://developer.android.com/guide/topics/resources/runtime-changes.html to handle configuration changes and to maintain your huge data between them...if all you need to maintain between the configuration change is just the settings,you can use the onSavedInstanceState() and onRestoreInstanceState() callbacks and the given bundles.