Kotlin custom attribute databinding
KotlinAndroid DatabindingKotlin Problem Overview
I am trying to set custom attribute using the Android DataBinding Library in my Kotlin project like this:
Layout
<ImageView
android:id="@+id/imgView”
android:layout_width="40dp"
android:layout_height="40dp"
android:layout_gravity="center"
android:adjustViewBounds="true"
app:imageUrl="@{segment.url}"/>
Code
class Utils {
companion object {
@BindingAdapter("bind:imageUrl")
@JvmStatic
fun loadImage(view: ImageView, url:String)
{Picasso.with(view.context).load(url).error(R.drawable.error).into(view)}
}
}
The runtime error I get is:
> A BindingAdapter in in
Any pointers to solve it?
This happens only for custom attributes. The rest of the databindings work fine
Kotlin Solutions
Solution 1 - Kotlin
Just keep function on the top level, no class or companion object needed, it will work since top-level functions in Kotlin translated to static member functions of Class named as FileNameKt
unless overridden by @file:JvmName
annotation
@BindingAdapter("imageUrl")
fun loadImage(view: ImageView, url:String) { ... }
One more option is to annotate Extension Function as @BindingAdapter
, it will work since in bytecode signature will exactly match signature expected by DataBindings(generated method will still accept an object of the extended class as the first argument), the function should remain top level as well
@BindingAdapter("imageUrl")
fun ImageView.loadImage(url:String) { ... }
One more option is to combine BindingAdapter
with the extension property like following:
@set:BindingAdapter("visible")
var View.visible
get() = visibility == VISIBLE
set(value) {
visibility = if (value) VISIBLE else GONE
}
Solution 2 - Kotlin
Try switching the order of the annotations. It seems to fix the issue:
class Utils {
companion object {
@JvmStatic @BindingAdapter("imageUrl")
fun loadImage(view: ImageView, url:String) { ... }
}
}
The problem is that the databindng compiler uses getCompanion().loadImage
otherwise*.
You can verify this in the generated com.your.package.databinding.*Binding
class
* After playing around a bit I noticed that this has nothing to do with the order of the annotations, but seems to be random. It seems to change whenever I hit "rebuild". It might be a bug in kapt
or in the kotlin compiler
Solution 3 - Kotlin
Adding @JvmStatic
after @BindingAdapter("imageUrl")
fixed my problem.
For ex:
@BindingAdapter("android:visibility")
@JvmStatic
fun setVisibility(view: View, visible: Boolean) {
view.visibility = if (visible) View.VISIBLE else View.GONE
}
}
Solution 4 - Kotlin
Or using extension:
@BindingAdapter("imageUrl")
fun ImageView.setImageUrl(url: String?) {
Picasso.with(context).load(url).into(this)
}
Now you can use this function anywhere else
Solution 5 - Kotlin
This worked for me
object ImageUtils {
@JvmStatic @BindingAdapter("imageUrl")
fun ImageView.loadImage(url: String?){
GlideHelper.loadImage(url,this)
}
}
in xml like this:
imageUrl="@{file.thumbnailLink}"
Solution 6 - Kotlin
This is working for me. Please find it below..
Add in gradle:
apply plugin: 'kotlin-kapt'
dependencies {
kapt "com.android.databinding:compiler:3.1.4"
}
Add in POJO:
companion object {
@BindingAdapter("image")
@JvmStatic
fun loadImage(view: ImageView, imageUrl: String) {
//am Using Glide
Glide.with(view.context).setDefaultRequestOptions(RequestOptions().circleCrop())
.load(imageUrl).into(view)
}
}
In Layout:
Add bind:image="@{movies.imageUrl}
<ImageView
android:id="@+id/imageView"
android:layout_width="100dp"
android:layout_height="100dp"
bind:image="@{movies.imageUrl}/>
Solution 7 - Kotlin
The function(loadImage) need to put in object(Singleton in java) not in class and set @JvmStatic
before @BindingAdapter("imageUrl")
like this :
<ImageView
android:id="@+id/imgView”
android:layout_width="40dp"
android:layout_height="40dp"
android:layout_gravity="center"
android:adjustViewBounds="true"
imageUrl="@{segment.url}"/>
@JvmStatic
@BindingAdapter("bind:imageUrl")
fun ImageView.loadImage( url:String) {
Picasso.with(this.context).load(url).error(R.drawable.error).into(this)
}