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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.
Here is my binding adapter:
@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()}"/>
and method in my ViewModel:
fun testFunction() = Unit
I have been struggling with this for a bit now and nothing I've tried works, so any help is appreciated.
938
To create a custom binding adapter, you need to create an extension function of the view that will use the adapter. Then, you add the @BindingAdapter annotation. You have to indicate the name of the view attribute that will execute this adapter as a parameter in the annotation.
Binding adapters are responsible for making the appropriate framework calls to set values. One example is setting a property value like calling the setText() method. Another example is setting an event listener like calling the setOnClickListener() method.
android.databinding.InverseBindingAdapter. InverseBindingAdapter is associated with a method used to retrieve the value for a View when setting values gathered from the View.
Use function: Runnable instead of function: () -> Unit.
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.
On the other hand, () -> Unit looks like kotlin.jvm.functions.Function0 which is a function which takes 0 inputs and returns Unit.INSTANCE.
As you can see these two function signatures don't match, and that's why the compilation fails.
116
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