Kotlin custom attribute databinding

Question

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 <package.Utils.Companion> is not static and requires an object to use, retrieved from the DataBindingComponent. If you don't use an inflation method taking a DataBindingComponent, use DataBindingUtil.setDefaultComponent or make all BindingAdapter methods static.

Any pointers to solve it?

This happens only for custom attributes. The rest of the databindings work fine

Stepango · Accepted Answer · 2020-09-27T03:01:53.080

124

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
    }

edited Sep 27 '20 at 03:01

answered Oct 18 '16 at 04:40

Stepango

4,721
3
31
44

2

This answer is still giving me error. Lovis' answer worked for me. – omerjerk Sep 19 '17 at 07:35
What about lambdas? How can I assign lambda function in xml layout for custom BindingAdapter in Kotlin? – Владимир Широков Oct 27 '17 at 08:17
@ВладимирШироков yes you can, same as `onClick` works for Views in XML, you'll just need proper SAM class/interface https://developer.android.com/reference/android/databinding/BindingAdapter.html – Stepango Nov 03 '17 at 08:41
What about the use of `@JvmStatic`? – IgorGanapolsky Nov 09 '19 at 19:05
1

@IgorGanapolsky all top-level functions is `static` so you don't need to declare it as `@JvmStatic` – Stepango Nov 10 '19 at 07:47

score 43 · Answer 2 · answered Oct 17 '16 at 14:04

43

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

answered Oct 17 '16 at 14:04

Lovis

9,513
5
31
47

Same here, changing the order does not help. – luca992 Oct 17 '16 at 22:40
4

I put a kotlin bug report up https://youtrack.jetbrains.com/issue/KT-14417 – luca992 Oct 17 '16 at 23:24
4

Binding look for static method and on providing @JvmStatic inside companion object fixes the problem – Dharmendra Jadon Oct 09 '17 at 06:00
Why do we have to have **companion object**? – IgorGanapolsky Nov 09 '19 at 19:05
@IgorGanapolsky nobody said you _have to_ (see accepted answer), but that's how the question was asked. – Lovis Nov 12 '19 at 11:49
@Lovis Then there is no need for `@JvmStatic` – IgorGanapolsky Nov 12 '19 at 14:13

score 14 · Answer 3 · edited Nov 03 '19 at 19:02

14

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
    }
}

edited Nov 03 '19 at 19:02

Bahaa KA

157
1
12

answered Jan 04 '18 at 18:12

Andrii Kovalchuk

4,351
2
36
31

This is worked for me thank you so much – KGeeks Dec 15 '21 at 06:07

score 3 · Answer 4 · answered Mar 21 '18 at 20:22

3

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

answered Mar 21 '18 at 20:22

Yazazzello

6,053
1
19
21

You need @JvmStatic – IgorGanapolsky Nov 09 '19 at 19:06
3

@IgorGanapolsky you need '@JvmStatic' only if you are going to call it from Java code, it's for interop only. https://kotlinlang.org/docs/reference/java-to-kotlin-interop.html – Yazazzello Nov 11 '19 at 11:22

Dhanalakshmi · Answer 5 · 2019-11-13T08:06:58.843

3

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}/>

edited Nov 13 '19 at 08:06

answered Nov 04 '19 at 07:15

Dhanalakshmi

39
7

Why do you have back-ticks around @BindingAdapter? – IgorGanapolsky Nov 09 '19 at 19:07
@igorganapolsky sorry.. Typo – Dhanalakshmi Nov 13 '19 at 08:08
There is absolutely no need for **companion object** with BindingAdapter – IgorGanapolsky Nov 13 '19 at 17:13
we should give companion object.. bcz we use @JvmStatic. otherwise we get an error. – Dhanalakshmi Nov 14 '19 at 05:07
`@JvmStatic` is not a requirement – IgorGanapolsky Nov 14 '19 at 14:39
JvmStatic is must. Without @JvmStatic getting error like "make all BindingAdapter methods static. please check out. – Dhanalakshmi Nov 14 '19 at 16:53

score 2 · Answer 6 · answered Nov 12 '18 at 21:48

2

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)
}

answered Nov 12 '18 at 21:48

Fidan Bacaj

408
5
10

This requires companion object – IgorGanapolsky Nov 09 '19 at 19:06
1

'@JvmStatic' handle that, '@JvmStatic' its like companion object ! – Fidan Bacaj Nov 12 '19 at 17:08

score 2 · Answer 7 · answered May 31 '19 at 19:45

2

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}"

answered May 31 '19 at 19:45

Yogesh Choudhary Paliyal

604
1
8
23

Kotlin custom attribute databinding

Layout

Code

7 Answers7

Linked