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我正在尝试实现两个应该像 Radiogroup 一样的 MaterialCardViews。因此，如果我单击一个，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供以后使用（通过电子邮件发送）。

我成功编写了 .xml 并实现了检查逻辑，但我很难实现取消检查逻辑。

XML，用于更好可见性的简短版本

<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>

视图模型

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()
    }
}

我感谢每一个帮助，非常感谢！

PS：如果有更好更简单的方法来实现这一点，例如告诉视图中的viewModel保存isChecked，请通知我。MaterialCardView 默认实现了“isChecked”，但没有逻辑。

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1 回答 1

0

好的，我已经解决了问题：

一、更改绑定适配器

我实际上没有看到任何方法可以使用双向数据绑定来实现上述编写的案例。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!!
        }
    }
}

二、改变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>

三、改变viewmodel

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
    }
}

四、将clickListener添加到XML或者Fragment（这里是Fragment）

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

如果有人有任何问题，请写在评论中，我会提供帮助。

于 2020-08-27T16:28:41.867 回答