Kotlin-android：未解决的参考数据绑定

Question

I have following fragment class written in Java using the new databinding library

import com.example.app.databinding.FragmentDataBdinding;

public class DataFragment extends Fragment {

    @Nullable
    private FragmentDataBinding mBinding;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        mBinding = DataBindingUtil.inflate(inflater, R.layout.fragment_data, container, false);
        return mBinding.getRoot();
    }
}

It compiles and runs fine.
I tried to rewrite it in Kotlin and came up with the following:

import com.example.app.databinding.FragmentDataBdinding

class ProfileFragment : Fragment() {

    private var mBinding: FragmentDataBinding? = null

    override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        mBinding = DataBindingUtil.inflate(inflater, R.layout.fragment_data, container, false)
        return mBinding!!.getRoot()
    }
}

But now step :app:compileDebugKotlin outputs the following:

Error:(16, 38) Unresolved reference: databinding
Error:(37, 27) Unresolved reference: FragmentDataBinding

How can I use android-databinding library with Kotlin?

My top-level build.gradle :

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:1.3.0'
        classpath 'com.android.databinding:dataBinder:1.0-rc4'
    }
}

allprojects {
    repositories {
        jcenter()
    }
}

My build.gradle in app dir (only relevant parts):

apply plugin: 'com.android.application'
apply plugin: 'com.android.databinding'
apply plugin: 'kotlin-android'

dependencies {
    compile "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
}

buildscript {
    ext.kotlin_version = '0.14.451'
    repositories {
        mavenCentral()
    }

    dependencies {
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
        classpath "org.jetbrains.kotlin:kotlin-android-extensions:$kotlin_version"
    }
}
repositories {
    mavenCentral()
    maven {
        url 'http://oss.sonatype.org/content/repositories/snapshots'
    }
}

I'm using Android Studio 1.4, Build tools version 23.0.1, Android SDK 23, SDK tools 24.4.0

Answer 1

Try use this configuration:

In main build.gradle :

buildscript {
    ext.kotlin_version = '<kotlin-version>'
    ext.android_plugin_version = '2.2.0-alpha4'
    dependencies {
        classpath "com.android.tools.build:gradle:$android_plugin_version"
    //... rest of the content
    }
}

App build.gradle :

android {
    dataBinding {
        enabled = true
    }
}

dependencies {
    kapt "com.android.databinding:compiler:$android_plugin_version"
}

kapt {
    generateStubs = true
}

Answer 2

I found new solution, hope it will helps you.

First of all check whether plugin applied:

apply plugin: 'kotlin-kapt'

then

android {
    ...
    ...
    dataBinding {
        enabled = true
    }
    ...
    ...
}

You might have an error in dependency:

USE

kapt 'com.android.databinding:compiler:3.1.4'

instead of

compile 'com.android.databinding:compiler:3.1.4'

You can visit here for new version

Thank you.

Answer 3

Update 2: This is a really old answer, instead refer to lrampazzo's answer.

It works with 1.0-rc4, put

kapt 'com.android.databinding:compiler:1.0-rc4' 

into your dependencies

Thanks Ghedeon, for the link in comments

Update : Here's a really simple hello world example project

Answer 4

The version of Data Binding compiler is same as gradle version in your project build.gradle file:

// at the top of file 
apply plugin: 'kotlin-kapt'


android {
  dataBinding.enabled = true
}

dependencies {
  kapt "com.android.databinding:compiler:3.0.0-beta1"
}

and the gradle version is

classpath 'com.android.tools.build:gradle:3.0.0-beta1'

Here is an example link to complete using of databinding library in kotlin.

https://proandroiddev.com/modern-android-development-with-kotlin-september-2017-part-1-f976483f7bd6

Answer 5

To Solve the problem, you have to put

apply plugin: 'kotlin-kapt'

at the top of build.gradle (Module: app), then put this line in dependencies

kapt "com.android.databinding:compiler:[YOUR_ANDROID_PLUGIN_VERSION]"

You can find android plugin version by go to menu

File > Project Structure > Project

Then Sync Again. If you see this warning, ignore it.

3rd-party Gradle plug-ins may be the cause

Answer 6

Try this.Andrid studio 2.0(2.1)

In build.gradle

android{
   dataBinding {
        enabled = true
    }
...
}
dependencies {
 kapt 'com.android.databinding:compiler:2.0.0-rc1'
....
}

kapt {
    generateStubs = true
}

In my project: buildToolsVersion = "23.0.3"

in top level build.gradle

dependencies {
        classpath 'com.android.tools.build:gradle:2.0.0'
    }

Answer 7

this work for me in androidStudio ver3.1.3

apply plugin: 'kotlin-kapt'

dataBinding {
    enabled = true
}

Answer 8

In my case, this solved my problem.

I added this in the app build.gradle:

buildFeatures {
    dataBinding true
    viewBinding true 
}

Answer 9

Configuration data binding in kotlin

build.gradle (folder app)

apply plugin: 'kotlin-kapt'

android {
   ...
   dataBinding {
      enabled = true
   }
}

dependencies {
   // data binding
   kapt "com.android.databinding:compiler:3.1.3"
}

Enjoy Kotlin...

Answer 10

Important Update

You can see in documentation of Android.

The new compiler in version 3.2 is enabled by default.

So Just Update your Android Studio to V3.2 or newer . and remove all unnecessary config.

So just enable dataBinding in app level build.gradle .

android {
    dataBinding {
        enabled = true
    }
}

It will do all things for you automatically.

You can SAFELY REMOVE below lines-

• Remove databinding.compiler

   kapt 'com.android.databinding:compiler:3.0.1'

• Remove kapt

   kapt { generateStubs = true }

My complete config

build.gradle (Project)

kotlin_version = '1.2.71'    
classpath 'com.android.tools.build:gradle:3.2.0'

Use gradle latest version . Use kotlin latest version .

build.gradle (App)

apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'

compileSdkVersion 28
targetSdkVersion 28

implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"

Important Do not just copy and paste config. See this answer for setting up Kotlin version.

gradle-wrapper.properties

distributionUrl=https\://services.gradle.org/distributions/gradle-4.6-all.zip

Answer 11

在我的例子中，错误是Unresolved reference: RegisterationUserBinding我只是使用我的布局名称fragment_registeration_user像这个FragmentRegisterationUserBinding并在数据绑定布局中使用它，错误消失了。

Answer 12

In the Gradle module file add this

android {
    ...
    buildFeatures {
        dataBinding true
    }
}

To use databinding in Kotlin you need to configure your app to use data binding, enable the dataBinding build option in your build.gradle file in the .app module and you can replace your code with this:

import com.example.app.databinding.FragmentDataBdinding

class ProfileFragment : Fragment() {

    private lateint var mBinding: FragmentProfileBinding

    override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        mBinding = DataBindingUtil.inflate(inflater, R.layout.fragment_data, container, false)

        return mBinding.getRoot()
    }
}

For more help check the databinding documentation link: https://developer.android.com/topic/libraries/data-binding .

Answer 13

Add following in you app build.gradle

kapt "com.android.databinding:compiler:$android_plugin_version"
apply plugin: 'kotlin-kapt' // This one at top where plugin belong to

This will do the trick.

$android_plugin_version is version of com.android.tools.build:gradle in application build.gradle

Also, add this to your module build.gradle

android { /// Existing Code kapt { generateStubs = true } }

Answer 14

尝试将此添加到您的gradle.properties

android.databinding.enableV2=true

Answer 15

Add Databinding in android Project using when you have use kotlin language.

Below steps

--First you need to add the below plugin

**apply plugin: 'kotlin-kapt'**

--Second dataBinding enabled true

**dataBinding {
        enabled = true
    }**

All this point added in app.build.gradle after hit "SYNC NOW"

Lets For example you have edit profile activity then how to define binding variable in kotlin??

lateinit var buildProfileBinding: ActivityBuildProfileBinding

buildProfileBinding = getBinding()

Here,get binding is method to handle which type of binding object

protected <T extends ViewDataBinding> T getBinding() {
                return (T) binding;
            }

Answer 16

In my case, adding

kapt {
    generateStubs = true
}

Solved the problem for me. I ignored it the first time, I thought it's irrelevant to the problem:

Unresolved reference databinding

But now, data-binding is working just fine.

Answer 17

I want to share my own expirience. To use data databinding with Kotlin in android studio is enough to add

dataBinding {
    enabled = true
}

After that "sync it" and, it's very important, to "make Project". After that all your object will be active to use.

Answer 18

在尝试使用 FragmentDetailsBinding 之前，您必须确保通过将整个布局包装在 "" 标记父项中并将所有 xmlns 移动到布局标记然后构建项目，从而将相应的布局（ fragment_details.xml ）转换为数据绑定布局

Answer 19

In my case I only forgot to add in layout file the header:

<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">

....

Answer 20

If you have applied the following from the documentation :

android {
    ...
    buildFeatures {
        dataBinding true
    }
}

In your module's gradle.properties and still get this error message, it's probably because of missing XML data tags .

This is especially the case if you created a ListFragment through Android Studio's Fragment Gallery, one expects Android Studio would automatically convert the layout file for a binding adapter to a binding layout but it DOES NOT and it sure looks like a bug, not fixed as of version 4.2.2!

Nevertheless here's the fix:

1. Open up the corresponding XML file (in my case the compiler was nagging about AlarmItemBinding missing reference, so the XML would be alarm_item.xml
2. Right click on the top-level tag (in my case <LinearLayout...> select Show Context Actions
3. Select Convert to data binding layout
4. Select Build -> Clean project
5. Select Build -> Rebuild project

Answer 21

In your Gradle module (app) file add

android {
    ...
    buildFeatures {
        dataBinding true
    }
}

BTW, keep in mind: Generated view binding name is based on name of your layout file, NOT on name of your class!

That means, if you have MainActivity class with corresponding activity_main.xml , the binding will be called ActivityMainBinding .

Also, do not forget to initialize your binding variable by adding

binding = ActivityMainBinding.inflate(layoutInflater)

into your onCreate() method.

Do not forget to add this as well:

setContentView(binding.root)

instead of setContentView(R.layout.activity_main) (that would cause your listeners to not work at all)

Answer 22

Add below build features in your app build.gradle file

android {... buildFeatures { viewBinding true } }

Then in your activity onCreate method

binding = ActivityMainBinding.inflate(layoutInflater) setContentView(binding.root)