Android DataBinding / BindingAdapter Error: { missing return statement }

Question

Android DataBinding / BindingAdapter Error: An error is thrown: error: missing return statement when passing a function to BindingAdapter (block: () -> Unit).

BindingAdapter.kt

@BindingAdapter("click")
fun LottieAnimationView.click(block: () -> Unit) {
    setOnClickListener {
        block()
    }
}

activity_main.xml

<data>
    <variable
        name="viewModel"
        type="com.veldan.ViewModel" />
</data>

<View
        android:id="@+id/view"
        click="@{() -> viewModel.viewFun()}"
        android:layout_width="0dp"
        android:layout_height="0dp"   />

<View
        android:id="@+id/view"
        click="@{() -> viewModel.viewFun()}"
        android:layout_width="0dp"
        android:layout_height="0dp"   />

ViewModel.kt

class ViewModel() {
     viewFun(){
        // logic
     }
}

Boken · Accepted Answer · 2021-12-12 22:24:40Z

6

SOLUTION 1:

Use Field syntax

Function syntax: ❌

| click = "@{ () -> viewModel.viewFun() }"

Field syntax: ✅

| click = "@{ viewModel.viewFun }"

SOLUTION 2:

Use Lambda

| ViewModel.kt

class ViewModel() {
    val viewFun: () -> Unit = {
        // logic
     }
}

Lambda - works well when block with parameters.

| block with parameters

@BindingAdapter("click")
fun LottieAnimationView.click(block: (Param1, Param2, ...) -> Unit) {
    setOnClickListener {
        block()
    }
}

edited Dec 12, 2021 at 22:24

Boken

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answered May 5, 2021 at 15:29

Владислав Шестернин

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Collectives™ on Stack Overflow

Android DataBinding / BindingAdapter Error: { missing return statement }

1 Answer 1

SOLUTION 1:

| click = "@{ () -> viewModel.viewFun() }"

| click = "@{ viewModel.viewFun }"

SOLUTION 2:

| ViewModel.kt

| block with parameters

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Collectives™ on Stack Overflow

1 Answer 1

SOLUTION 1:

| click = "@{ () -> viewModel.viewFun() }"

| click = "@{ viewModel.viewFun }"

SOLUTION 2:

| ViewModel.kt

| block with parameters

Comments

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