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Kotlin Property Delegate for Fragment view lifecycle binding
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fun <T> Fragment.viewLifecycle(bindUntilEvent: Lifecycle.Event = Lifecycle.Event.ON_DESTROY): ReadWriteProperty<Fragment, T> = | |
object: ReadWriteProperty<Fragment, T>, LifecycleObserver { | |
// A backing property to hold our value | |
private var binding: T? = null | |
private var viewLifecycleOwner: LifecycleOwner? = null | |
init { | |
// Observe the View Lifecycle of the Fragment | |
this@viewLifecycle | |
.viewLifecycleOwnerLiveData | |
.observe(this@viewLifecycle, Observer { newLifecycleOwner -> | |
viewLifecycleOwner | |
?.lifecycle | |
?.removeObserver(this) | |
viewLifecycleOwner = newLifecycleOwner.also { | |
it.lifecycle.addObserver(this) | |
} | |
}) | |
} | |
@OnLifecycleEvent(Lifecycle.Event.ON_ANY) | |
fun onDestroy(event: Lifecycle.Event) { | |
if (event == bindUntilEvent) { | |
// Clear out backing property just before onDestroyView | |
binding = null | |
} | |
} | |
override fun getValue( | |
thisRef: Fragment, | |
property: KProperty<*> | |
): T { | |
// Return the backing property if it's set | |
return this.binding!! | |
} | |
override fun setValue( | |
thisRef: Fragment, | |
property: KProperty<*>, | |
value: T | |
) { | |
// Set the backing property | |
this.binding = value | |
} | |
} | |
} | |
override fun setValue(thisRef: Any, property: KProperty<*>, value: T) { | |
this.property = value | |
} | |
} |
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