Android View Lifecycle Extensions
Extensions for Android View class that let you access a view lifecycle without having to create a custom view (extend a View)
Dependency
app/build.gradle
dependencies {
implementation "com.gorisse.thomas:android-view-lifecycle:1.0.1"
}
Usage
View Class Kotlin Extensions
No need for custom view since all properties and functions are defined as View extensions.
val lifecycle = findViewById(R.id.frameLayout).lifecycle
val imageView = ImageView(context)
imageView.lifecycleScope.launchWhenCreated {
(imageView.parent as View).isVisible = true
loadSlideShow(imageView.width, imageView.height)
}
View Lifecycle
Listen or execute when a View lifecycle state occurred
- Invoke an action every time the view becomes resumed
view.lifecycle.addObserver(onResume = {
refreshData()
})
- Invoke actions once, when the view is at least at a state
view.doOnResume {
startWelcomeAnimation(view)
}
view.doOnPause {
stopWelcomeAnimation(view)
}
= If the view is already resumed the action will be performed immediately, otherwise the action will be performed after the view is next resumed In all the cases, your action will be invoked only one time.
- Perform an action when the view is destroyed:
view.doOnDestroy {
removeListener(view)
}
View LifecycleScope
Launch a coroutine and auto cancel it when the view sate is destroyed
- Launches and runs the given block when the view Lifecycle state is at least resumed. The returned Job will be cancelled when the view is destroyed.
texView.lifecycleScope.launchWhenCreated { // Launch on Dispatchers.Main
val data = withContext(Dispatchers.IO) { // Dispatchers.IO for background task
loadNetworkData() // Suspend function making http calls
}
texView.text = data // Dispatchers.Main for UI change
}
= When the view is detached or the Fragment or FragmentActivity container is destroyed, if loadNetworkData() is not finished, the network call is cancelled.
- Launch a repeating call and auto cancel it when the view is destroyed (TimerTask Coroutine equivalent). The returned Job will be cancelled when the view is destroyed.
textView.lifecycleScope.launchWhenCreated {
while (isActive) {
view.text = "${System.currentTimeMillis()}" // Dispatchers.Main
withContext(Dispatchers.IO) { // Dispatchers.IO for waiting in background
delay(1000) // Wait 1 second
}
}
}
= When the view is detached or the Fragment or FragmentActivity container is destroyed, the while loop stops.
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