如何在Android Studio的数据绑定中将值传递给android.view.View.OnClickListener的变量？

Question

The following code is from the project sunflower .

There is variable named clickListener , it's a variable of android.view.View.OnClickListener .

I don't know how to pass a value to the variable clickListener of android.view.View.OnClickListener in data binding in Android Studio, could you tell me?

And more, I can't understand that the code binding.setClickListener{...} in PlantAdapter.kt, could you tell me?

list_item_plant.xml

<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools">

    <data>
        <variable
            name="clickListener"
            type="android.view.View.OnClickListener"/>
        ...
    </data>

    <com.google.samples.apps.sunflower.views.MaskedCardView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"      
        android:onClick="@{clickListener}"
       
    ...
}

PlantAdapter.kt

class PlantAdapter : ListAdapter<Plant, RecyclerView.ViewHolder>(PlantDiffCallback()) {    
    ...
    class PlantViewHolder(
        private val binding: ListItemPlantBinding
    ) : RecyclerView.ViewHolder(binding.root) {
        init {
            binding.setClickListener {
                binding.plant?.let { plant ->
                    navigateToPlant(plant, it)
                }
            }
        }

     ...
}

Added content

Normally, I define a data binding variable name in plain_activity_solution_2.xml , I should assign a value for it such as binding.name = "Ada" in PlainOldActivitySolution2.kt .

So when I define a data binding variable clickListener in list_item_plant.xml , I should assign a value for it such as binding.clickListener=... in PlantAdapter.kt , But I can't find binding.clickListener=... in PlantAdapter.kt , instead I only find binding.setClickListener {...} , why?

plain_activity_solution_2.xml

<layout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        xmlns:tools="http://schemas.android.com/tools">

    <data>    
        <variable
            name="name"
            type="String"/>    
    </data>

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <TextView
            android:id="@+id/plain_name"
            android:layout_width="0dp"
            android:layout_height="wrap_content"                
            android:text="@{name}"
     ...
}

PlainOldActivitySolution2.kt

class PlainOldActivitySolution2 : AppCompatActivity() {

    // Obtain ViewModel from ViewModelProviders
    private val viewModel by lazy { ViewModelProviders.of(this).get(SimpleViewModel::class.java) }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        val binding: PlainActivitySolution2Binding =
            DataBindingUtil.setContentView(this, R.layout.plain_activity_solution_2)

        binding.name = "Ada"
        binding.lastName = "Lovelace"
       
    }

    ...
}

Answer 1

I don't understand what variable you're trying to pass, and why.

But to pass any variable you can use a lambda expression like this:

 android:onClick="@{() -> clickListener(someVariable, someOtherVariable)}"

If you need the view, you can pass it like that:

 android:onClick="@{(view) -> clickListener(view)}"

Answer 2

The binding is there own class, normally android View.OnClickListener is passing just Button as casted View , you can't add more, but you can listen with View.OnClickListener then find real object and pass to your own listeners.