Databinding V2和kotlin，我找不到我的BT？

Question

昨天，我将我的 Android Studio 更新到了 3.1。所以我只能使用Databinding V2。我可以在Java中成功构建。但在Kotlin中失败。它告诉我Unresolved reference: BR

布局

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
    <data>
        <variable
            name="mainViewModel"
            type="com.example.shao.myapplication.ViewModel" />
    </data>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{mainViewModel.title}"/>
    </LinearLayout>
</layout>

在 Java 中

public class MainActivity2 extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    ActivityMainBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
    binding.setVariable(BR.mainViewModel, new ViewModel());
}


public static int getMainBr() {
    return BR.mainViewModel;
}

}

在科特林中

class MainActivity : AppCompatActivity() {

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    val mBinding = DataBindingUtil.setContentView<ActivityMainBinding>(this, R.layout.activity_main)
    mBinding.setVariable(BR.mainViewModel, ViewModel())
}
}

Answer 1

Android 与 Kotlin 的数据绑定

首先，在 Android Studio 中创建好 Android 项目后，我们需要将 Data Binding 和 Kotlin 的依赖添加到我们应用的 build.gradle 文件中。

apply plugin: 'kotlin-android'                       
apply plugin: 'kotlin-kapt'
android {
....
dataBinding {
    enabled = true
}
}
dependencies {
...
// notice that the compiler version must be the same than our gradle version
kapt 'com.android.databinding:compiler:2.3.1'
}

首先我们需要创建一个模型。在这种情况下，一个基本的像 User.kt

data class User(val name: String, val age: Int)

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>

    <variable
        name="user"
        type="com.kuma.sample.User"
        />
</data>

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.kuma.sample.MainActivity"
    >

    <TextView
        android:id="@+id/user_name_text_view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:padding="16dp"
        android:text="@{user.name}"
        tools:text="Name"
        />

    <TextView
        android:id="@+id/user_age_text_view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:padding="16dp"
        android:text="@{Integer.toString(user.age)}"
        tools:text="XX"
        />

</LinearLayout>

 </layout>

Kotlin 类

package com.kuma.sample

 import android.databinding.DataBindingUtil
 import android.os.Bundle
 import android.support.v7.app.AppCompatActivity
 import com.kuma.kotlinsteps.databinding.ActivityMainBinding

 class MainActivity : AppCompatActivity() {

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    val binding: ActivityMainBinding = DataBindingUtil.setContentView(this, R.layout.activity_main)

    val user = User("Kuma", 23)
    binding.setVariable(BR.user, user)
    binding.executePendingBindings()
}

}

解决错误

enter code hereapply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'
 android {
compileSdkVersion 24
buildToolsVersion "24.0.0"

defaultConfig {
applicationId "com.example.icarusud.recyclerviewtest"
minSdkVersion 15
targetSdkVersion 24
versionCode 1
versionName "1.0"
}
buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
}
dataBinding {
    enabled true
}
sourceSets {
    main.java.srcDirs += 'src/main/kotlin'
}
}
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
testCompile 'junit:junit:4.12'
compile 'com.android.support:appcompat-v7:24.1.1'
compile "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"

//recyclerview
compile "com.android.support:recyclerview-v7:24.1.1"

 //lastadapter
  compile 'com.github.nitrico.lastadapter:lastadapter:1.1.1'

kapt "com.android.databinding:compiler:2.1.2"
}
repositories {
mavenCentral()
}

kapt { generateStubs = true }

根据下面的代码更改你的 gradle 设置试试这个代码它可以帮助你。

Answer 2

改变

mBinding.setVariable(BR.mainViewModel, ViewModel())

到

mBinding.mainViewModel=ViewModel()