CODEWITHSUNDEEP
androidkotlinandroid-mvvm
George Mathew K
George Mathew K

Reputation: 1580

Android : Kotlin : MVVM : Why viewModel.onButtonClicked() causes the app crash?

Logcat Message :

java.lang.IllegalStateException: Could not find method @={() -> viewModel.onBtnClicked()(View) in a parent or ancestor Context for android:onClick attribute defined on view class androidx.appcompat.widget.AppCompatButton with id 'button'

File1 : activity_main.xml

<data>
    <variable
        name="viewModel"
        type="com.wingsquare.databindingdemo.MainViewModel" />
</data>

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

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        android:onClick = "@={() -> viewModel.onBtnClicked()"
        />
</androidx.constraintlayout.widget.ConstraintLayout>

File 2 : MainActivity.kt

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

    val binding: ActivityMainBinding = DataBindingUtil.setContentView(this,R.layout.activity_main)

    // val binding = ActivityMainBinding.inflate(layoutInflater)
    val mainViewModel = ViewModelProvider(this).get(MainViewModel::class.java)
    binding.viewModel = mainViewModel
    binding.lifecycleOwner = this
}

}

File 3 : MainViewModel.kt

class MainViewModel : ViewModel() {

fun onBtnClicked() {
    Log.d("MainViewModel", "MainViewModel")
}

}

Upvotes: 1

Views: 599

Answers (2)

ArMot
ArMot

Reputation: 168

The Logcat Message is some how misleading. I was facing the same error for couple of hours checking everything else I thought it be the root cause. But for this particular error, all you have to do is to keep an eye on "{ }". This is one of the drawbacks of data binding in android. lots of the times you don't get any error on compile times, And if you do! that's not really helpful !

and another thing to consider is that '=' in

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

is used for a two way binding. you don't need it in this case. you can read about it here on android official docs

Upvotes: 1

هيثم
هيثم

Reputation: 1081

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

  • Add a parenthesis at the end.
  • also you may want to remove the equal sign after the @

Upvotes: 0

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