如何通过数据绑定使用 sealed class 类型的可变实时数据

Question

我正在尝试使用具有数据绑定的密封类型 class 的可变 LiveData 来处理 ProgressBar 的可见性，但出现以下错误。

cannot find symbol variable sealed class

下面是我的代码

视图模型

    class RevampSplashViewModel: RevampBaseViewModel() {

    val splashEvents = MutableLiveData<SplashEvents>()

    sealed class SplashEvents {
        object Loading : SplashEvents()
        object Success : SplashEvents()
        data class Error(val message: String): SplashEvents()
    }
}

布局

    <?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        tools:context=".revamp.ui.splash.RevampSplashActivity">

    <data>
        <import type="revamp.ui.splash.RevampSplashViewModel.SplashEvents"/>
        <variable
                name="vm"
                type="revamp.ui.splash.RevampSplashViewModel" />
    </data>

    <androidx.constraintlayout.widget.ConstraintLayout
            android:background="@color/colorAccent"
            android:layout_width="match_parent"
            android:layout_height="match_parent">

        <ProgressBar
                android:id="@+id/progress_bar"
                android:theme="@style/progressBarWhite"
                android:visibility="@{vm.splashEvents == SplashEvents.Loading}"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintBottom_toBottomOf="parent"
                android:layout_width="@dimen/progressbar_dimen"
                android:layout_height="@dimen/progressbar_dimen" />

    </androidx.constraintlayout.widget.ConstraintLayout>

</layout>

下面是我面临的确切错误。

error: cannot find symbol
                
vmSplashEventsRevampUiSplashRevampSplashViewModelSplashEventsLoading = (vmSplashEventsGetValue) == (revamp.ui.splash.RevampSplashViewModel.SplashEvents.Loading); 


error: illegal parenthesized expression

vmSplashEventsRevampUiSplashRevampSplashViewModelSplashEventsLoading = (vmSplashEventsGetValue) == (revamp.ui.splash.RevampSplashViewModel.SplashEvents.Loading);

Answer 1

我意识到我在比较不兼容的数据类型。解决方法是我们必须使用 instanceof 而不是 ==。下面是代码。

    <?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        tools:context=".revamp.ui.splash.RevampSplashActivity">

    <data>
        <import type="revamp.ui.splash.RevampSplashViewModel.SplashEvents"/>
        <variable
                name="vm"
                type="revamp.ui.splash.RevampSplashViewModel" />
    </data>

    <androidx.constraintlayout.widget.ConstraintLayout
            android:background="@color/colorAccent"
            android:layout_width="match_parent"
            android:layout_height="match_parent">

        <ProgressBar
                android:id="@+id/progress_bar"
                android:theme="@style/progressBarWhite"
                android:visibility="@{vm.splashEvents instanceof SplashEvents.Loading}"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintBottom_toBottomOf="parent"
                android:layout_width="@dimen/progressbar_dimen"
                android:layout_height="@dimen/progressbar_dimen" />

    </androidx.constraintlayout.widget.ConstraintLayout>

</layout>

如何通过数据绑定使用 sealed class 类型的可变实时数据

How to use mutable live data of type sealed class with data binding

android

android-databinding

android-livedata

sealed-class

mutablelivedata