在FacebookLogin中使用kotlin时,“未解决的参考”背后的原因是什么?

当我试图执行附图中的代码时,我总是收到“未解析的引用:FacebookCallback”错误。

在这里输入图像说明

我正在尝试按照以下链接指示设置Facebook登录: https : //developers.facebook.com/docs/facebook-login/android#addbutton

我是Kotlin的新手,但我看不出我在这里做错了什么。

编辑:

这是我的gradle文件:

apply plugin: 'com.android.application' apply plugin: 'kotlin-android' apply plugin: 'com.neenbedankt.android-apt' android { compileSdkVersion 24 buildToolsVersion "24.0.0" defaultConfig { applicationId "yetti.yetti" minSdkVersion 23 targetSdkVersion 24 versionCode 1 versionName "1.0" testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner" } buildTypes { release { minifyEnabled false proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro' } } sourceSets { main.java.srcDirs += 'src/main/kotlin' androidTest.java.srcDirs += 'src/androidTest/kotlin' } dexOptions { javaMaxHeapSize "2048M" } compileOptions.incremental = false } kapt { generateStubs = true } 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 "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version" compile 'com.android.support:appcompat-v7:24.0.0' compile 'com.android.support.constraint:constraint-layout:1.0.0-alpha4' compile 'com.jakewharton:butterknife:8.2.1' compile 'com.facebook.android:facebook-android-sdk:4.14.0' compile 'com.google.firebase:firebase-core:9.2.1' compile 'com.google.firebase:firebase-database:9.2.1' compile 'com.google.firebase:firebase-auth:9.2.1' testCompile 'junit:junit:4.12' kapt 'com.jakewharton:butterknife-compiler:8.2.1' } // Add to the bottom of the file apply plugin: 'com.google.gms.google-services' 

和:

 // Top-level build file where you can add configuration options common to all sub-projects/modules. buildscript { ext.kotlin_version = '1.0.3' repositories { jcenter() mavenCentral() } dependencies { classpath 'com.android.tools.build:gradle:2.2.0-alpha6' classpath 'com.google.gms:google-services:3.0.0' // the latest version of the android-apt plugin classpath 'com.neenbedankt.gradle.plugins:android-apt:1.8' classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version" } } allprojects { repositories { jcenter() } } task clean(type: Delete) { delete rootProject.buildDir } 

此外,这是我试图执行的等效代码,但用普通的Java编写(工作正常):

 import com.facebook.FacebookCallback; import com.facebook.FacebookException; import com.facebook.login.LoginResult; public class Actv extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_actv); FacebookCallback facebookCallback = new FacebookCallback() { @Override public void onSuccess(LoginResult loginResult) { } @Override public void onCancel() { } @Override public void onError(FacebookException error) { } }; } } 

在Kotlin匿名实现FacebookCallback正确方法如下:

 val facebookCallback = object : FacebookCallback { override fun onSuccess(loginResult: LoginResult) { } override fun onCancel() { } override fun onError(error: FacebookException) { } } 

对象expression式和声明文档提供了所有必要的细节。