数据绑定，MaterialCardView应该像Radiogroup

问题描述

我正在尝试实现两个MaterialCardViews，它们应该像Radiogroup一样工作。因此，如果我单击其中一个，则应取消选中另一个。我正在使用viewModel，liveData和自定义双向数据绑定来保存这些值以备后用（每封电子邮件发送）。

我成功编写了.xml并实现了检查逻辑，但是我却难以实现取消检查逻辑。

XML，简短版本可提供更好的可见性

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

    <data>
        <variable
            name="vm"
            type="com.example.app.data.viewmodel.EmailViewModel" />
    </data>

        <com.google.android.material.card.MaterialCardView
            android:id="@+id/cardViewOne"
            android:checkable="true"
            android:clickable="true"
            android:focusable="true"
            <!-- Custom Two way databinding -->
            app:state_checked="@={vm.cardOptionOneChecked}"
        </com.google.android.material.card.MaterialCardView>


        <com.google.android.material.card.MaterialCardView
            android:id="@+id/cardViewTwo"
            android:checkable="true"
            android:clickable="true"
            android:focusable="true"
            <!-- Custom Two way databinding -->
            app:state_checked="@={vm.cardOptionTwoChecked}">

        </com.google.android.material.card.MaterialCardView>
</layout>

ViewModel

class EmailViewModel @ViewModelInject constructor(
    @Assisted private val savedStateHandle: SavedStateHandle
) : ViewModel() {

    // Variable for Id = cardViewOne
    val cardOptionOneChecked = MutableLiveData<Boolean>()
    
    // Variable for Id = cardViewTwo
    val cardOptionTwoChecked = MutableLiveData<Boolean>()
}

CardViewAdapter.kt

@BindingAdapter("state_checked")
fun setStateChecked(view: MaterialCardView,liveData: MutableLiveData<Boolean>) {
    if (view.isChecked != liveData.value) {
        liveData.value = view.isChecked
    }
}

@InverseBindingAdapter(attribute = "state_checked")
fun getStateChecked(view: MaterialCardView,): Boolean {
    return view.isChecked
}

// I don't know what logic belongs here to make it work! 
// Current approach just checks the current view and does nothing more. How can I save the last
// checked value?
@BindingAdapter("state_checkedAttrChanged")
fun setCheckedAttrListener(
    view: MaterialCardView,attrChange: InverseBindingListener,) {
    view.apply {
        setOnClickListener { view.isChecked = true }
        setOnCheckedChangeListener { card,isChecked ->
            if (card.isChecked && card != view) {
                card.isChecked = false
            }
        }
        attrChange.onChange()
    }
}

感谢您的帮助，非常感谢！

P.S：如果有更好，更轻松的方式来实现这一目标，例如从视图中告诉viewModel保存isChecked，请通知我。 MaterialCardView默认情况下实现了“ isChecked”，但没有逻辑。

解决方法

好的，我已经解决了问题：

首先，更改绑定适配器

我实际上看不到使用双向数据绑定来实现上述书面案例的任何方法。这是新的绑定适配器

// View = Clicked MaterialCard,liveData = value in viewModel
@BindingAdapter("state_checked")
fun setStateChecked(view: MaterialCardView,liveData: MutableLiveData<Boolean>) {
    if (view.isChecked != liveData.value) {
        if (liveData.value != null) {
            view.isChecked = liveData.value!!
        }
    }
}

第二，更改XML布局，因为我们不再使用双向数据绑定

<layout
        xmlns:app="http://schemas.android.com/apk/res-auto">
    
        <data>
            <variable
                name="vm"
                type="com.example.app.data.viewmodel.EmailViewModel" />
        </data>
    
            <com.google.android.material.card.MaterialCardView
                android:id="@+id/cardViewOne"
                android:checkable="true"
                android:clickable="true"
                android:focusable="true"
                <!-- Deleted "=" -->
                app:state_checked="@{vm.cardOptionOneChecked}"
            </com.google.android.material.card.MaterialCardView>
    

            <com.google.android.material.card.MaterialCardView
                android:id="@+id/cardViewTwo"
                android:checkable="true"
                android:clickable="true"
                android:focusable="true"
                <!-- Deleted "=" -->
                app:state_checked="@{vm.cardOptionTwoChecked}">
    
            </com.google.android.material.card.MaterialCardView>
    </layout>

第三，更改视图模型

class EmailViewModel @ViewModelInject constructor(
    @ApplicationContext context: Context,@Assisted private val savedStateHandle: SavedStateHandle
) : ViewModel() {

    val cardOptionOneChecked = MutableLiveData<Boolean>()
    
    val cardOptionTwoChecked = MutableLiveData<Boolean>()

    // Added
     fun firstCardClicked() {
        cardOneChecked.value = true
        cardTwoChecked.value = false
    }

    fun secondCardClicked() {
        cardOneChecked.value = false
        cardTwoChecked.value = true
    }
}

第四，将clickListener添加到XML或Fragment（此处为Fragment）

cardViewOne.setOnClickListener {
    viewModel.firstCardClicked()
}
cardViewTwo.setOnClickListener {
    viewModel.secondCardClicked()
}

如果有人有任何疑问，请将其写在评论中，我会帮忙的。