Android 更改可见性时是否不更新LiveData?
主要活动Android 更改可见性时是否不更新LiveData?,android,data-binding,android-livedata,android-mvvm,Android,Data Binding,Android Livedata,Android Mvvm,主要活动 override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) activityMainBinding = DataBindingUtil.setContentView(this, R.layout.activity_main) mainViewModel = ViewModelProviders.of( this@MainActi
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
activityMainBinding = DataBindingUtil.setContentView(this,
R.layout.activity_main)
mainViewModel = ViewModelProviders.of(
this@MainActivity,
mainViewModelFactory
)[MainViewModel::class.java]
activityMainBinding.viewmodel = mainViewModel
activityMainBinding.lifecycleOwner = this
mainViewModel.fetchBusinessList()
mainViewModel.businessList.observe(this, Observer { items ->
run {
mainViewModel.isLoading.value = false
}
})
主视图模型
class MainViewModel(val repository: MainActivityRepo) : ViewModel() {
val isLoading: MutableLiveData<Boolean> = MutableLiveData()
lateinit var businessList: LiveData<List<Content>>
fun fetchBusinessList() {
isLoading.value = true
businessList = repository.getBusinessList()
}
class MainViewModel(val存储库:MainActivityReporto):ViewModel(){
val isLoading:MutableLiveData=MutableLiveData()
lateinit var业务列表:LiveData
有趣的商业列表(){
isLoading.value=true
businessList=repository.getBusinessList()
}
布局
<androidx.core.widget.ContentLoadingProgressBar
android:id="@+id/clp_fetching"
style="@style/Widget.AppCompat.ProgressBar"
android:layout_width="40dp"
android:layout_height="40dp"
android:visibility="@{viewmodel.isLoading?View.VISIBLE:View.GONE}"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
我尝试了
setValue
,postValue
,还添加了LifeCycleOwner
,它不会影响false的可见性。关于ViewModel用户的一些观察
您正试图从“活动”更新视图模型中的属性,但不应更新该属性
视图模型
class MainViewModel(val repository: MainActivityRepo) : ViewModel() {
val isLoading: MutableLiveData<Boolean> = MutableLiveData()
lateinit var businessList: LiveData<List<Content>>
fun fetchBusinessList() {
isLoading.value = true
businessList = repository.getBusinessList()
}
// This is where you the content of the list would be received
fun onListUpdated(contentList : List<Content>){
businessList.value = contentList;
isLoading.value = false;
}
无论何时更改
isLoading
的值,都必须手动调用executePendingBindings()
或者,您可以使用自定义绑定适配器来实现此功能:
@BindingAdapter("mutableVisibility")
fun setMutableVisibility(view: View, visibility: MutableLiveData<Boolean>?) {
val parentActivity: AppCompatActivity? = view.getParentActivity()
if (parentActivity != null && visibility != null) {
visibility.observe(parentActivity, Observer { value -> view.visibility = if(value) View.VISIBLE else View.GONE})
}
}
@BindingAdapter(“可变可见性”)
fun setMutableVisibility(视图:视图,可见性:MutableLiveData?){
val parentActivity:AppCompatActivity?=view.getParentActivity()
if(parentActivity!=null&&visibility!=null){
可见性.observe(父活动,观察者{value->view.visibility=if(value)view.VISIBLE else view.GONE})
}
}
然后在布局中:
<androidx.core.widget.ContentLoadingProgressBar
android:id="@+id/clp_fetching"
style="@style/Widget.AppCompat.ProgressBar"
android:layout_width="40dp"
android:layout_height="40dp"
app:mutableVisibility="@{viewmodel.isLoading}"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
我在你的问题中看不到任何postValue
或与可见性相关的代码。请看最后一行,我已经尝试了所有选项,设置为true效果很好。@VivekMishraVIew.Goe
。我在视图中看到I的大写错误更正了,这是复制问题时的键入错误,这不是问题。@ViVEKMISHARTRY调用executePendingBinding()“将val
更改为var
”在上面的代码段中,没有理由这样做,您没有使用executePendingBindings
不,没有必要。它通过观察LiveData自动处理executePendingBindings()
应该根据您的实现使用,而不是我的实现
<androidx.core.widget.ContentLoadingProgressBar
android:id="@+id/clp_fetching"
style="@style/Widget.AppCompat.ProgressBar"
android:layout_width="40dp"
android:layout_height="40dp"
app:mutableVisibility="@{viewmodel.isLoading}"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />