作为绑定适配器的高阶函数的问题 [英] Issue with higher order function as a binding adapter

问题描述

我在尝试使用Kotlin/Android数据绑定在绑定适配器中将函数用作参数时遇到问题.如果在日志中没有其他有用信息的情况下进行构建，则此示例代码将引发e: error: cannot generate view binders java.lang.StackOverflowError.

I am running into issues trying to take a function as a parameter in a binding adapter using Kotlin/Android databinding. This example code throws e: error: cannot generate view binders java.lang.StackOverflowError when building with no other useful info in the log.

这是我的绑定适配器:

@JvmStatic
@BindingAdapter("onDelayedClick")
fun onDelayedClick(view: View, function: () -> Unit) {
    // TODO: Do something
}

XML:

        <View
            android:id="@+id/test_view"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            app:onDelayedClick="@{() -> viewModel.testFunction()}"/>

和ViewModel中的方法:

and method in my ViewModel:

fun testFunction() = Unit

我已经为此苦苦挣扎了一段时间，但我没有尝试过，因此可以提供任何帮助.

I have been struggling with this for a bit now and nothing I've tried works, so any help is appreciated.

推荐答案

使用function: Runnable代替function: () -> Unit.

Android的数据绑定编译器会生成Java代码，您的kotlin函数的签名类似于void testFunction()，因为kotlin在从Java调用时会将Unit调整为void.

Android's data-binding compiler generates java code, to which, your kotlin function's signature looks like void testFunction(), as kotlin adapts Unit as void when calling from java.

另一方面，() -> Unit看起来像kotlin.jvm.functions.Function0，该函数需要0个输入并返回Unit.INSTANCE.

On the other hand, () -> Unit looks like kotlin.jvm.functions.Function0 which is a function which takes 0 inputs and returns Unit.INSTANCE.

如您所见，这两个函数签名不匹配，这就是编译失败的原因.

As you can see these two function signatures don't match, and that's why the compilation fails.

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