milimonster.blogg.se - Android life cycle components

#Android life cycle components update
#Android life cycle components for android
#Android life cycle components android
#Android life cycle components code

The framework keeps the ViewModel alive as long as the scope of the LifecycleOwner is alive. This refers to an instance of LifecycleOwner. = new ViewModelProvider(this).get(ChronometerViewModel.class) Open ChronoActivity2 and examine how the class retrieves and uses a ViewModel: ChronometerViewModel chronometerViewModel Persisting the state of the Chronometer using a ViewModel A ViewModel is also better suited to managing tasks related to network communication, as well as data manipulation and persistence. Activities and fragments are short-lived objects which are created and destroyed frequently as a user interacts with an app. As the previous step demonstrates, an activity is a poor choice to manage app data. You can use a ViewModel to retain data across the entire lifecycle of an activity or a fragment. This timer is reset when a configuration change, such as screen rotation, destroys an activity. In the previous step, you ran an activity that displays a timer. In this step, you use a ViewModel to persist state across screen rotations and address the behaviour you observed in the previous step. You can use a ViewModel because instances of this class survive configuration changes, such as screen rotation.

#Android life cycle components update

You now need to update the app to persist state across screen rotations.

#Android life cycle components android

Note: If you're using an emulator or device running Android 8.0 or higher, you'll need to enable rotation in settings:

Rotate the screen and notice that the timer resets!.

The app runs and displays a screen similar to the following screenshot:

Run the Step 1 run configuration on a device or emulator.

Once you have run the command, you should see run configurations for each step: idea/runConfigurations/ĬOPY runConfigurations\*. idea/runConfigurationsĬp runConfigurations/*.

Copy over the Android Studio run configurations that will be used in this codelab.

Open the project Android Studio version 2.5 or newer.

$ git clone you can download the repository as a Zip file:

#Android life cycle components code

In this step, you download the code for the entire codelab and then run a simple example app. You begin with a sample app and add code through a series of steps, integrating the various architecture components as you progress.

In this codelab, you implement examples of each of the components described above. To proceed, you must be familiar with the Android activity lifecycle.

#Android life cycle components for android

This codelab has been designed for Android developers with some basic experience. To read an introductory guide to this topic, see LiveData. LiveData manages observer subscriptions by pausing subscriptions to stopped LifecycleOwner objects, and cancelling subscriptions to LifecycleOwner objects that are finished. LiveData respects the complex lifecycles of your app components, including activities, fragments, services, or any LifecycleOwner defined in your app.

LiveData - allows you to observe changes to data across multiple components of your app without creating explicit, rigid dependency paths between them.

To read an introductory guide to this topic, see Handling Lifecycles. You can subscribe other components to owner objects which implement this interface, to observe changes to the lifecycle of the owner.

LifecycleOwner - LifecycleOwner is an interface implemented by the AppCompatActivity and Fragment classes.

To read an introductory guide to this topic, see ViewModel. A ViewModel typically stores the state of a view's data and communicates with other components, such as data repositories or the domain layer which handles business logic.

ViewModel - provides a way to create and retrieve objects that are bound to a specific lifecycle.

This codelab introduces you to the following lifecycle-aware architecture components for building Android apps: Architecture components are a set of Android libraries that help you structure your app in a way that is robust, testable, and maintainable.