无法使用数据绑定从 xml 调用方法 ViewModel isValidate()

Question

使用绑定表达式可以正常禁用按钮，但是当它很长时我需要将它移动到 ViewModel 中的方法，这就是它无法正常工作的地方。

<com.google.android.material.button.MaterialButton
    android: id = "@ + id / btValidateLegalRepresentativeCE"
    style = "@ style / BasicMaterialButton"
    android: layout_width = "match_parent"
    android: layout_marginTop = "21dp"
    android: enabled = "@ {viewModel.documentLiveData.length()> 0 &amp; viewModel.firstNameLiveData.length()> 0 &amp; viewModel.lastNameLiveData.length()> 0} "

来自 ViewModel 的方法调用

<com.google.android.material.button.MaterialButton
    android: id = "@ + id / btValidateLegalRepresentativeCE"
        style = "@ style / BasicMaterialButton"
        android: layout_width = "match_parent"
        android: layout_marginTop = "21dp"
        app: enabled = "@ {viewModel.isValidate()}" />

视图模型

private val _documentLiveData = MutableLiveData("")
val documentLiveData: MutableLiveData<String> get() = _documentLiveData

private val _firstNameLiveData = MutableLiveData("")
val firstNameLiveData: LiveData<String> get() = _firstNameLiveData

private val _lastNameLiveData = MutableLiveData("")
val lastNameLiveData: LiveData<String> get() = _lastNameLiveData

fun isValidate(): Boolean {
    val document = documentLiveData.value?.length ?: 0
    val firstName = firstNameLiveData.value?.length ?: 0
    val lastName = lastNameLiveData.value?.length ?: 0
    return (document > 0) && (firstName > 0) && (lastName > 0)
}

我考虑如下：

binding.viewModel = viewModel

binding.lifecycleOwner = this

感谢您的帮助。

Answer 1

要在视图模型中调用函数，您需要使用 ()->

app:enabled = "@ {()->viewModel.isValidate()}

如果上述方法不起作用，请创建自定义绑定适配器。

在java中，会像

 @androidx.databinding.BindingAdapter("android:viewModel")
public static void setButtonEnable(Button button,YourViewModel viewModel) {
     if(viewModel.isValidate())
      //if true ,enable button
      button.setEnable(true);
     
  else 
    //disable button
     button.setEnable(false);
     }

从布局中调用此自定义适配器并将视图模型传递给适配器。

<com.google.android.material.button.MaterialButton
    android: id = "@ + id / btValidateLegalRepresentativeCE"
        style = "@ style / BasicMaterialButton"
        android: layout_width = "match_parent"
        android: layout_marginTop = "21dp"
        android:viewModel= "@{viewModel}" />

无法使用数据绑定从 xml 调用方法 ViewModel isValidate()

Cannot call method ViewModel isValidate() from xml with dataBinding

data-binding

android

viewmodel