'Event 등록' ACC

1. Event 클래스 등록

import androidx.lifecycle.Observer

/**
 * Used as a wrapper for data that is exposed via a LiveData that represents an event.
 */
open class Event<out T>(private val content: T) {
    @Suppress("MemberVisibilityCanBePrivate")
    var hasBeenHandled = false
        private set // Allow external read but not write
    /**
     * Returns the content and prevents its use again.
     */
    fun getContentIfNotHandled(): T? {
        return if (hasBeenHandled) {
            null
        } else {
            hasBeenHandled = true
            content
        }
    }

    /**
     * Returns the content, even if it's already been handled.
     */
    fun peekContent(): T = content
}
/**
 * An [Observer] for [Event]s, simplifying the pattern of checking if the [Event]'s content has
 * already been handled.
 *
 * [onEventUnhandledContent] is *only* called if the [Event]'s contents has not been handled.
 */
class EventObserver<T>(private val onEventUnhandledContent: (T) -> Unit) : Observer<Event<T>> {
    override fun onChanged(event: Event<T>?) {
        event?.getContentIfNotHandled()?.let {
            onEventUnhandledContent(it)
        }
    }
}

 

2. ViewModel에 호출 함수 등록

fun openTask(taskId: String) {
	_openTaskEvent.value = Event(taskId)
}

fun completeTask(task: Task, completed: Boolean) = viewModelScope.launch {
	if (completed) {
		tasksRepository.completeTask(task)
        showSnackbarMessage(R.string.task_marked_complete)
    } else {
        tasksRepository.activateTask(task)
        showSnackbarMessage(R.string.task_marked_active)
	}
}

 

3. XML 데이터 바인딩

<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <data>

        <import type="android.widget.CompoundButton" />

        <variable
            name="task"
            type="com.example.android.architecture.blueprints.todoapp.data.Task" />

        <variable
            name="viewmodel"
            type="com.example.android.architecture.blueprints.todoapp.tasks.TasksViewModel" />
    </data>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="?android:attr/listPreferredItemHeight"
        android:orientation="horizontal"
        android:paddingLeft="@dimen/activity_horizontal_margin"
        android:paddingRight="@dimen/activity_horizontal_margin"
        android:paddingBottom="@dimen/list_item_padding"
        android:paddingTop="@dimen/list_item_padding"
        android:onClick="@{() -> viewmodel.openTask(task.id)}">

        <CheckBox
            android:id="@+id/complete_checkbox"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_vertical"
            android:onClick="@{(view) -> viewmodel.completeTask(task, ((CompoundButton)view).isChecked())}"
            android:checked="@{task.completed}" />
        <TextView
            android:id="@+id/title_text"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_gravity="center_vertical"
            android:layout_marginLeft="@dimen/activity_horizontal_margin"
            android:layout_marginStart="@dimen/activity_horizontal_margin"
            android:textAppearance="@style/TextAppearance.AppCompat.Title"
            android:text="@{task.titleForList}"
            app:completedTask="@{task.completed}" />
    </LinearLayout>
</layout>

4. Activity 또는 Fragment에 Event 관찰 등록 클래스 등록

private fun setupNavigation() {
	viewModel.openTaskEvent.observe(viewLifecycleOwner,
    	EventObserver {
        	navigateToDetailsFragment(it)
    	})
}