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 · 2020-09-27 03:01:53Z

125

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, 2020 at 3:01

answered Oct 18, 2016 at 4:40

Stepango

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5 Comments

omerjerk Over a year ago

This answer is still giving me error. Lovis' answer worked for me.

Владимир Широков Over a year ago

What about lambdas? How can I assign lambda function in xml layout for custom BindingAdapter in Kotlin?

Stepango Over a year ago

@ВладимирШироков yes you can, same as onClick works for Views in XML, you'll just need proper SAM class/interface developer.android.com/reference/android/databinding/…

IgorGanapolsky Over a year ago

What about the use of @JvmStatic?

Stepango Over a year ago

@IgorGanapolsky all top-level functions is static so you don't need to declare it as @JvmStatic

Lovis · Accepted Answer · 2016-10-17 14:04:40Z

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, 2016 at 14:04

Lovis

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6 Comments

luca992 Over a year ago

Same here, changing the order does not help.

luca992 Over a year ago

I put a kotlin bug report up youtrack.jetbrains.com/issue/KT-14417

Dharmendra Jadon Over a year ago

Binding look for static method and on providing @JvmStatic inside companion object fixes the problem

IgorGanapolsky Over a year ago

Why do we have to have companion object?

Lovis Over a year ago

@IgorGanapolsky nobody said you have to (see accepted answer), but that's how the question was asked.

|

Bahaa KA · Accepted Answer · 2019-11-03 19:02:20Z

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 3, 2019 at 19:02

Bahaa KA

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answered Jan 4, 2018 at 18:12

Andrii Kovalchuk

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Comments

Yazazzello · Accepted Answer · 2018-03-21 20:22:27Z

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, 2018 at 20:22

Yazazzello

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2 Comments

IgorGanapolsky Over a year ago

You need @JvmStatic

Yazazzello Over a year ago

@IgorGanapolsky you need '@JvmStatic' only if you are going to call it from Java code, it's for interop only. kotlinlang.org/docs/reference/java-to-kotlin-interop.html

Dhanalakshmi · Accepted Answer · 2019-11-13 08:06:58Z

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, 2019 at 8:06

answered Nov 4, 2019 at 7:15

Dhanalakshmi

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6 Comments

IgorGanapolsky Over a year ago

Why do you have back-ticks around @BindingAdapter?

Dhanalakshmi Over a year ago

@igorganapolsky sorry.. Typo

IgorGanapolsky Over a year ago

There is absolutely no need for companion object with BindingAdapter

Dhanalakshmi Over a year ago

we should give companion object.. bcz we use @JvmStatic. otherwise we get an error.

IgorGanapolsky Over a year ago

@JvmStatic is not a requirement

|

Fidan Bacaj · Accepted Answer · 2018-11-12 21:48:18Z

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, 2018 at 21:48

Fidan Bacaj

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2 Comments

IgorGanapolsky Over a year ago

This requires companion object

Fidan Bacaj Over a year ago

'@JvmStatic' handle that, '@JvmStatic' its like companion object !

Yogesh Choudhary Paliyal · Accepted Answer · 2019-05-31 19:45:35Z

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, 2019 at 19:45

Yogesh Choudhary Paliyal

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