Hopefully, there's a BackHandler composable (added in Activity Compose in 1.3.0-alpha02) that configures it for us. We have to enable this callback when we want to handle a back press, which disables other callbacks in the chain of responsibility.

It is also not scalable in Single-Activity architectures.Ī more elegant way is to create an OnBackPressedCallback and add it to the OnBackPressedDispatcher that controls dispatching system back presses. We could emit an action in the overridden Activity.onBackPressed(), but it is ugly and not recommended solution. Given the fact that we use Jetpack Compose Navigation (or we use the FragmentManager), we have a back stack and Android will navigate user up to the previous destination.īut what if we want to intercept the default Back behavior, emitting a SelectBack action and thus handle it in the same way as the click on the TopAppBar navigation icon? What if a user presses the system back button instead of the navigation icon? It's a high time to answer the following question: It's not the responsibility of the UI layer to think about the consequences of emitting that action. Then, depending on the business logic, it might navigate up to the parent destination or do something else. Apart from the default tap action of a notification which opens the app we can also set other actions that can be completed directly from the notifications. You can hide the status bar on Android 4.0 (API level 14) and lower by setting WindowManager flags. Hide the Status Bar on Android 4.0 and Lower. You should never show the action bar without the status bar. The expression passed in the top Detail() function emits a SelectBack action and it's consumed by a DetailViewModel instance. Figure 2 shows an app with a hidden status bar.

As you can see above, the DetailTopAppBar contains the IconButton composable function that invokes the onBack lambda. This pattern also fits incredibly well with Jetpack Compose. It showcases a simple unidirectional data flow, which is a recommended pattern for modelling the UI state and user interaction. It can also be used for navigation in your application. It can display the activity title, icon, actions which can be triggered, additional views and other interactive items. It can be freely positioined into your layout file. Enter fullscreen mode Exit fullscreen mode The toolbar bar(formerly known as action bar) is represented as of Android 5.0 via the Toolbarview group.

Android handle buttonbar action