Cannot find method for data binding event using lambda

the signature of the method has to be the same in the viewModel,

I was using

android:onClick="@{v -> viewModel.settingsClick()}"

and the method in the viewModel was

 public void settingsClick() {
   ...
}

Apparently the data binding generated classes were in a bad state and weren't getting properly regenerated, invalidating caches and cleaning fixed the problem.

As you noted in your comment about the android:onClick="@{vm::doIt}" solution, your onClick handler must have a View parameter, even if you don't use it.

Your workaround of calling your parameter-less buttonClicked method via a lambda will work nicely, so long as the lambda accepts the View parameter. This is easy. Unused parameters to lambdas can be named "_" for clarity. So your onClick handler can be configured thus:

android:onClick="@{_ -> vm.buttonClicked()}"