kotlin - 在使用 Android 数据绑定(bind)和 Kotlin 的自定义 BindingAdapter 中使用 lambda

Question

我正在尝试使用 Kotlin 为 Android 数据绑定(bind)的 lambda 处理程序进行自定义绑定(bind)。只要我的 ViewModel 处理程序显式返回 Void，它就可以正常工作。但如果它返回 Kotlin Unit，我会得到 error: cannot generate view binders java.lang.StackOverflowError .

一切似乎都正确连接，因为所有其他自定义绑定(bind)都有效(convertBooleanToViewVisibility、toTestString 甚至 customOnClick，只要我调用 onClickVoid [参见下面的示例])。

问题是当我试图在我的应用程序中调用返回 Unit 的 lambda 时:customOnClick 而不是返回 Void。在下面的例子中，它是调用 mainViewModel.onClick()而不是 mainViewModel.onClickVoid() .必须有一种方法让它工作，因为 android:onClick 能够调用 Unit版本。但是，如果我对 customOnClick 调用 onClick 使用相同的语法，我会收到此错误:

:app:kaptGenerateStubsDebugKotlin
Using kotlin incremental compilation
:app:kaptDebugKotlin
e: error: cannot generate view binders java.lang.StackOverflowError
e: 

e:      at android.databinding.tool.writer.Scope.access$getCurrentScope$cp(LayoutBinderWriter.kt:49)
e:      at android.databinding.tool.writer.Scope$Companion.getCurrentScope(LayoutBinderWriter.kt:58)
e:      at android.databinding.tool.writer.LayoutBinderWriterKt.scopedName(LayoutBinderWriter.kt:196)
e:      at android.databinding.tool.expr.Expr.toCode(Expr.java:776)
e:      at android.databinding.tool.writer.LayoutBinderWriterKt$callbackLocalName$2.invoke(LayoutBinderWriter.kt:203)
e:      at android.databinding.tool.writer.LayoutBinderWriterKt$callbackLocalName$2.invoke(LayoutBinderWriter.kt)
e:      at android.databinding.tool.ext.LazyExt.getValue(ext.kt:27)
e:      at android.databinding.tool.writer.LayoutBinderWriterKt.getCallbackLocalName(LayoutBinderWriter.kt)
e:      at android.databinding.tool.writer.LayoutBinderWriterKt.scopedName(LayoutBinderWriter.kt:197)
e: java.lang.IllegalStateException: failed to analyze: java.lang.RuntimeException: failure, see logs for details.
cannot generate view binders java.lang.StackOverflowError
    at android.databinding.tool.writer.Scope.access$getCurrentScope$cp(LayoutBinderWriter.kt:49)
    at android.databinding.tool.writer.Scope$Companion.getCurrentScope(LayoutBinderWriter.kt:58)
    at android.databinding.tool.writer.LayoutBinderWriterKt.scopedName(LayoutBinderWriter.kt:196)
    at android.databinding.tool.expr.Expr.toCode(Expr.java:776)
    at android.databinding.tool.writer.LayoutBinderWriterKt$callbackLocalName$2.invoke(LayoutBinderWriter.kt:203)
    at android.databinding.tool.writer.LayoutBinderWriterKt$callbackLocalName$2.invoke(LayoutBinderWriter.kt)
    at android.databinding.tool.ext.LazyExt.getValue(ext.kt:27)
    at android.databinding.tool.writer.LayoutBinderWriterKt.getCallbackLocalName(LayoutBinderWriter.kt)
    at android.databinding.tool.writer.LayoutBinderWriterKt.scopedName(LayoutBinderWriter.kt:197)
    .............................. (TRUNCATED)  ...................................
    at android.databinding.tool.expr.Expr.toCode(Expr.java:776)
    at android.databinding.tool.writer.LayoutBinderWriterKt$callbackLocalName$2.invoke(LayoutBinderWriter.kt:203)
    at android.databinding.tool.writer.LayoutBinderWriterKt$callbackLocalName$2.invoke(LayoutBinderWriter.kt)
    at android.databinding.tool.ext.LazyExt.getValue(ext.kt:27)
    at android.databinding.tool.writer.LayoutBinderWriterKt.getCallbackLocalName(LayoutBinderWriter.kt)
    at android.databinding.tool.writer.LayoutBinderWriterKt.scopedName(LayoutBinderWriter.kt:197)

    at org.jetbrains.kotlin.analyzer.AnalysisResult.throwIfError(AnalysisResult.kt:57)
    at org.jetbrains.kotlin.cli.jvm.compiler.KotlinToJVMBytecodeCompiler.compileModules(KotlinToJVMBytecodeCompiler.kt:144)
    at org.jetbrains.kotlin.cli.jvm.K2JVMCompiler.doExecute(K2JVMCompiler.kt:167)
    at org.jetbrains.kotlin.cli.jvm.K2JVMCompiler.doExecute(K2JVMCompiler.kt:55)
    at org.jetbrains.kotlin.cli.common.CLICompiler.exec(CLICompiler.java:182)
    at org.jetbrains.kotlin.daemon.CompileServiceImpl.execCompiler(CompileServiceImpl.kt:397)
    at org.jetbrains.kotlin.daemon.CompileServiceImpl.access$execCompiler(CompileServiceImpl.kt:99)
    at org.jetbrains.kotlin.daemon.CompileServiceImpl$compile$1$2.invoke(CompileServiceImpl.kt:365)
    at org.jetbrains.kotlin.daemon.CompileServiceImpl$compile$1$2.invoke(CompileServiceImpl.kt:99)
    at org.jetbrains.kotlin.daemon.CompileServiceImpl$doCompile$2$$special$$inlined$withValidClientOrSessionProxy$lambda$1.invoke(CompileServiceImpl.kt:798)
    at org.jetbrains.kotlin.daemon.CompileServiceImpl$doCompile$2$$special$$inlined$withValidClientOrSessionProxy$lambda$1.invoke(CompileServiceImpl.kt:99)
    at org.jetbrains.kotlin.daemon.common.DummyProfiler.withMeasure(PerfUtils.kt:137)
    at org.jetbrains.kotlin.daemon.CompileServiceImpl.checkedCompile(CompileServiceImpl.kt:825)
    at org.jetbrains.kotlin.daemon.CompileServiceImpl.access$checkedCompile(CompileServiceImpl.kt:99)
    at org.jetbrains.kotlin.daemon.CompileServiceImpl$doCompile$2.invoke(CompileServiceImpl.kt:797)
    at org.jetbrains.kotlin.daemon.CompileServiceImpl$doCompile$2.invoke(CompileServiceImpl.kt:99)
    at org.jetbrains.kotlin.daemon.CompileServiceImpl.ifAlive(CompileServiceImpl.kt:1004)
    at org.jetbrains.kotlin.daemon.CompileServiceImpl.ifAlive$default(CompileServiceImpl.kt:865)
    at org.jetbrains.kotlin.daemon.CompileServiceImpl.doCompile(CompileServiceImpl.kt:791)
    at org.jetbrains.kotlin.daemon.CompileServiceImpl.access$doCompile(CompileServiceImpl.kt:99)
    at org.jetbrains.kotlin.daemon.CompileServiceImpl$compile$1.invoke(CompileServiceImpl.kt:364)
    at org.jetbrains.kotlin.daemon.CompileServiceImpl$compile$1.invoke(CompileServiceImpl.kt:99)
    at org.jetbrains.kotlin.daemon.CompileServiceImpl.ifAlive(CompileServiceImpl.kt:1004)
    at org.jetbrains.kotlin.daemon.CompileServiceImpl.ifAlive$default(CompileServiceImpl.kt:865)
    at org.jetbrains.kotlin.daemon.CompileServiceImpl.compile(CompileServiceImpl.kt:336)
    at sun.reflect.GeneratedMethodAccessor86.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:324)
    at sun.rmi.transport.Transport$1.run(Transport.java:200)
    at sun.rmi.transport.Transport$1.run(Transport.java:197)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.Transport.serviceCall(Transport.java:196)
    at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:568)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:826)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$0(TCPTransport.java:683)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:682)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)



    ... 39 more


FAILED

知道如何使它与 Unit 一起工作，所以我不需要更改我的 ViewModel 来显式返回 Void？对于我所有的处理程序？

示例项目

项目构建.gradle

buildscript {
    ext.kotlin_version = '1.1.3-2'
    ext.plugin_version = '2.3.3'

    repositories {
        jcenter()
    }

    dependencies {
        classpath "com.android.tools.build:gradle:$plugin_version"
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    }
}

allprojects {
    repositories {
        jcenter()
        mavenCentral()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

模块(应用程序)build.gradle

buildscript {
    repositories {
        jcenter()
        mavenCentral()
    }

    dependencies {
        classpath "org.jetbrains.kotlin:kotlin-android-extensions:$kotlin_version"
    }
}

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

android {
    compileSdkVersion 24
    buildToolsVersion "25.0.2"
    defaultConfig {
        applicationId "com.example.kotlindatabinding"
        minSdkVersion 24
        targetSdkVersion 24
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }

    dataBinding {
        enabled = true
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }

    sourceSets {
        main.java.srcDirs += 'src/main/kotlin'
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.android.support:appcompat-v7:26.+'
    compile 'com.android.support.constraint:constraint-layout:1.0.2'
    testCompile 'junit:junit:4.12'
    compile "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"

    kapt "com.android.databinding:compiler:$plugin_version"
}

kapt {
    generateStubs = true
}

MainActivity.kt

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        val binding = DataBindingUtil.setContentView<ActivityMainBinding>(this, R.layout.activity_main)
        binding.setMainViewModel(MainViewModel())
    }
}

主视图模型.kt

class MainViewModel {
    val myName: String
        get() {
            return "Hello world!"
        }

    fun onClick(){
        Log.i("ME", "Logging...")
    }

    fun onClickVoid(): Void? {
        onClick()
        return null as Void?
    }
}

绑定(bind).kt

object Bindings{
    @BindingConversion
    @JvmStatic fun convertBooleanToViewVisibility(isVisible: Boolean): Int {
        // Working
        return if (isVisible) View.VISIBLE else View.GONE
    }

    @BindingAdapter("customOnClick")
    @JvmStatic fun setOnItemClicked(textView: TextView, consumer: (String) -> Any?) {
        // Working
        consumer("test")
    }

    @JvmStatic fun toTestString(input: Any) : String {
        return "Test"
    }
}

activity_main.xml

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

    <data>
        <import type="com.example.kotlindatabinding.Bindings"/>
        <variable
            name="mainViewModel"
            type="com.example.kotlindatabinding.MainViewModel" />
    </data>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context="com.example.kotlindatabinding.MainActivity">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{Bindings.toTestString(mainViewModel.myName)}"
            android:visibility="@{mainViewModel.myName != null}"
            android:clickable="true"
            android:onClick="@{() -> mainViewModel.onClick()}"
            app:customOnClick="@{(someInput) -> mainViewModel.onClickVoid()}" />
    </LinearLayout>
</layout>

Answer 1

好吧，我想回复很晚，但其他人可能有同样的问题:
据我所知，这是一个错误的假设:数据绑定(bind)使用 Java，一般不了解 Kotlin。
为了通过数据绑定(bind)设置监听器，您必须使用带有方法的 Java 接口(interface)。 Kotlin lambdas 不像具有简单方法的 Java 接口(interface)，因为它们包含函数，这意味着它们总是返回一些东西(如果未指定，则返回 Unit)。

所以要实现设置监听器，在绑定(bind)适配器中定义一个简单的Java接口(interface)作为参数