Part 6 - ListView and the Activity Lifecycle

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last updated: 2017-08

Activities go through certain states as your application runs, such as starting up, running, being paused and being stopped. For more information, and specific guidelines on handling state transitions, see the Activity Lifecycle Tutorial. It is important to understand the activity lifecycle and place your ListView code in the correct locations.

All of the examples in this document perform ‘setup tasks’ in the Activity’s OnCreate method and (when required) perform ‘teardown’ in OnDestroy. The examples generally use small data sets that do not change, so re-loading the data more frequently is unnecessary.

However, if your data is frequently changing or uses a lot of memory it might be appropriate to use different lifecycle methods to populate and refresh your ListView. For example, if the underlying data is constantly changing (or may be affected by updates on other activities) then creating the adapter in OnStart or OnResume will ensure the latest data is displayed each time the Activity is shown.

If the Adapter uses resources like memory, or a managed cursor, remember to release those resources in the complementary method to where they were instantiated (eg. objects created in OnStart can be disposed of in OnStop).

Configuration Changes

It’s important to remember that configuration changes – especially screen rotation and keyboard visibility – can cause the current activity to be destroyed and re-created (unless you specify otherwise using the ConfigurationChanges attribute). This means that under normal conditions, rotating a device will cause a ListView and Adapter to be re-created and (unless you have written code in OnPause and OnResume) the scroll position and row selection states will be lost.

The following attribute would prevent an activity from being destroyed and recreated as a result of configuration changes:

[Activity(ConfigurationChanges="keyboardHidden|orientation")]

The Activity should then override OnConfigurationChanged to respond to those changes appropriately. For more details on how to handle configuration changes see the documentation.

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