data binding error ****msg:Cannot find the getter for attribute 'android:checked' with value type java.lang.Boolean on android.widget.CheckedTextView.
I have a Kotlin Android app and one of the XML layouts contains a CheckedTextView and I want to two-way bind the checked property to the checked value of the ViewModel. The idea is that the checked property in the viewModel will represent the one on the view itself. This fails with the error message above. Now I wonder whether this is because checked is a boolean value and the getter is called isChecked. Can Databinding not recognize that? So I tried extending it with a getChecked function, but that didn't resolve the error. Maybe because while Kotlin supports extension functions, Java does not. Any ideas how this can be solved?
XML file:
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
<data>
<variable name="viewModel"
type="lehrbaum.de.onenightcomps.view.SimpleCheckableListItemViewModel"/>
</data>
<CheckedTextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="#+id/textView"
android:padding="#dimen/text_margin"
android:gravity="center_vertical"
android:textStyle="bold"
android:checkMark="?android:attr/listChoiceIndicatorSingle"
android:checkMarkTint="#color/colorPrimary"
android:checked="#={viewModel.checked}"
android:text="#{viewModel.text}"/>
</layout>
ViewModel class:
class SimpleCheckableListItemViewModel {
val checked : MutableLiveData<Boolean> = MutableLiveData()
val text : MutableLiveData<String> = MutableLiveData()
}
Extension function:
fun CheckedTextView.getChecked(): Boolean {
return this.isChecked
}
There might be different reasons for this error but in my case, the problem raised up because I didn't add apply plugin: 'kotlin-kapt' And apply plugin: 'kotlin-android-extensions' in my Gradle.
After adding these plugins you have to replaced your annotationProcessors with kapt.
After that, every thing might be going well.
Related
I have made a binding adapter available statically inside my Fragment which basically change my button appearance from "Stop" to "Play" and vice-versa.
companion object {
#BindingAdapter("playState")
fun Button.setPlayState(item: UIState) {
item.let {
if (it.isPlaying) {
setText("Stop")
setBackgroundColor(ContextCompat.getColor(context, R.color.colorStop))
} else {
setText("Play")
setBackgroundColor(ContextCompat.getColor(context, R.color.colorPlay))
}
}
}
}
Here is my layout file. I have provided a data class for it.
<?xml version="1.0" encoding="utf-8"?>
<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>
<!-- stuff here -->
<variable
name="viewmodel"
type="com.mypackage.ui.ViewModel"/>
<variable
name="uistate"
type="com.mypackage.ui.UIState" />
</data>
<!-- layout, buttons, and more stuff here. Just pay attention to this following button -->
<Button
android:id="#+id/play_button"
android:layout_width="150sp"
android:layout_height="75sp"
android:layout_marginTop="20sp"
android:onClick="#{() -> viewmodel.onPlayClicked()}"
android:text="#string/play_button"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.498"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/minus_layout"
app:layout_constraintVertical_bias="0.026"
app:playState="#{uistate}"/>
</layout>
UIState itself is pretty self-explanatory.
data class UIState(var isPlaying: Boolean)
and the () -> viewmodel.onPlayClicked() flips the Boolean at UIState.
After compiling, Data Binding Compiler throws this error:
Cannot find a setter for <android.widget.Button app:playState>
that accepts parameter type 'com.mypackage.ui.UIState'
I have tried:
Rebuilding the project by removing .gradle folder
Looking for answer here and here.
Removed #JvmStatic annotation at the extension function
Moved the extension function to top level instead of Fragment's companion object.
I think you missed to add kotlin plugin in your gradle
apply plugin: 'kotlin-kapt'
You don't have to use #JvmStatic because you are using Kotlin extension feature.
You need to add the view reference as a paramater to your BindingAdapter method.
#BindingAdapter("playState")
fun setPlayState(button:Button,item: UIState) {
//do your work here
}
Your namespace
xmlns:app="http://schemas.android.com/apk/res-auto"
is wrong for custom binding adapters. Please use the namespace
xmlns:app="http://schemas.android.com/tools"
since app:playState is not in the namespace you have given its not working properly
I have been trying to use BindingAdapter in Android Studio 3.4 (the last update) with Kotlin for days now and nothing seems to work.
I first tried with the following tutorial: https://codelabs.developers.google.com/codelabs/android-databinding/#7
And it was outputing an error as soon as I reached the 8th step.
Furthermore I tried the simple example possible with an Empty Application, a single Activity, a single ViewModel, and a single BindingAdapter. Here is the XML code.
<?xml version="1.0" encoding="utf-8"?>
<layout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto">
<data>
<variable name="viewmodel"
type="com.example.testbindingadapter.DataViewModel"/>
</data>
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:greetings="#{viewmodel.name}"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
android:id="#+id/textView"/>
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>
Now here is the ViewModel with the BindingAdapter
class DataViewModel : ViewModel() {
private val _name = MutableLiveData<String>()
val name : LiveData<String> = _name
init {
_name.value = "Amath"
}
}
#BindingAdapter("greetings")
fun setName(view: TextView, text: String) {
view.text = "Welcome, $text"
}
I have also enabled dataBinging in my Graddle. I added apply plugin: 'kotlin-kapt' as suggested in the following thread Cannot find the setter for attribute in Data binding. At first I had an error msg:Cannot find the setter for attribute databinding subsequently the error disappeared, but the app simply crashed.
Can you help ?
You never set the viewmodel into databinding:
binding.viewmodel = viewModel
Via data-binding I am setting the visibility of a text field. The visibility is depending on a string being null or empty or nothing of the both.
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<data>
<import type="android.view.View"/>
<variable
name="viewModel"
type="com.example.viewModel"/>
</data>
<android.support.constraint.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
<TextView
android:id="#+id/textField1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="#{viewModel.data.text}"
android:visibility="#{(viewModel.data.text == null || viewModel.data.text.empty) ? View.GONE : View.VISIBLE}"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintBottom_toBottomOf="parent"/>
</android.support.constraint.ConstraintLayout>
Is it possible to create an import in the data element so that I can use the isNullOrBlank() function from the kotlin.text.Strings.kt class?
I was hoping to be able to use it like this: android:visibility="#{(viewModel.data.title.isNullOrBlank() ? View.GONE : View.VISIBLE}"
Android data binding still generates the Java code from the XML instead of the Kotlin code, once data binding will be migrated to generating Kotlin code instead of Java I believe we will be able to use Kotlin extension function in the XML, which will be really cool.
I am sure that gonna happen real soon as Google is pushing to Kotlin heavily. But for now, you have below
TextUtils.isEmpty() as mentioned by #Uli Don't forget to write an import.
The reason why you can't you use StringKt.isNullOrBlack in xml:
Below is the code from Kotlin String.kt
#kotlin.internal.InlineOnly
public inline fun CharSequence?.isNullOrEmpty(): Boolean {
contract {
returns(false) implies (this#isNullOrEmpty != null)
}
return this == null || this.length == 0
}
As you can see it is annotated with #kotlin.internal.InlineOnly which says the Java generated code of this method will be private.
InlineOnly means that the Java method corresponding to this Kotlin
function is marked private so that Java code cannot access it (which
is the only way to call an inline function without actual inlining
it).
It means it can't be called from Java and as data binding generated code is in JAVA it can't be used in data binding either. Thumb rule is what you can access from JAVA you can use that in data binding if not just use the old Java way I would say.
TextUtils.isEmpty() should do what you want.
I'm using Android Data Binding library to bind an xml layout that has an <include>
layout.xml
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
<data>
<variable
name="model"
type="com.example.MyViewModel" />
</data>
...
<include
layout="#layout/someOtherLayout"
android:id="#+id/includedLayout" />
...
</layout>
In the generated Databinding class for the xml I see this property:
#Nullable
public final com.example.databinding.SomeOtherLayoutBinding includedLayout;
Why is it annotated as #Nullable? The <include> is in the layout and as I see it, it is obviously non-null. What am I missing?
It forces me to use non-null assertion operator !! in Kotlin code when accessing the fields of the included layout and I'm wondering if it is safe or if there is something I'm not considering here
val binder = DataBindingUtil.bind(view)
val someView = binder.includedLayout!!.someView
According to the Documentation on View Binding, when you have multiple layouts for configuration changes, if the view is only present in some configurations, the binding class will be marked as nullable.
View Binding Docs
For the latest version of databinding compiler (3.1.0) to resolve that issue with nullable bindings of included layouts you could set
android.databinding.enableV2=true
in gradle.properties file inside your project.
After that you need invoke rebuild. After that all included layout bindings will be marked with #NonNull annotation.
What is the type of the Observable class property which getter is annotated as #Bindable in the Android Data Binding framework?
For example, let the Observable class be defined as follows:
class Localization() : BaseObservable() {
var translation: (key: String) -> String by Delegates.observable(defaultTranslation) { _, _, _ ->
notifyPropertyChanged(BR.translation)
}
#Bindable get
}
The layout XML will be then something like this:
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
<data>
<variable
name="translation"
type="WHAT IS THE TYPE OF TRANSLATION?" />
</data>
<FrameLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#{translation.invoke(stringKey)}" />
</FrameLayout>
</layout>
The question is, what to put in the type attribute of variable "translation".
I've tried:
type="kotlin.jvm.functions.Function1<String, String>"
It compiles, but the TextView is not updated when translation property changes.
I can achieve the desired behavior by introducing localization variable in the layout XML and then calling localization.translation.invoke() in the binding expression. I am just not comfortable with this and want to know if I can reference translation directly.
The Localization extends BaseObservable while Function1 is not observable at all. So using the Localization gives you an interface for observing the changes to the properties.
If you bind the translation, it's a simple field that gets set. If you want to update it, you'd have to call setTranslation() again.