【问题标题】：How to solve: "error: cannot find symbol class ..." after converting Java class to Kotlin?如何解决：将Java类转换为Kotlin后出现“错误：找不到符号类...”？
【发布时间】：2016-10-23 02:42:43
【问题描述】：

我正在尝试从 Kotlin 开始，将我项目的一些 Java 类转换为 Kotlin，并创建一个混合的 Java/Kotlin 项目。为了配置环境，我做了以下操作：

已下载最新版 Kotlin 插件 (1.0.2)；
在顶层 gradle.plugin 我添加了：classpath "org.jetbrains.kotlin:kotlin-android-extensions:1.0.2" 在依赖项部分；
在我的模块的 gradle 插件中，我在依赖项部分添加了：compile "org.jetbrains.kotlin:kotlin-stdlib:1.0.2"；
我选择了我想转换为 kotlin 的 POJO 类，从菜单 Code -> Convert Java File to Kotlin File 中选择；
之后，所有导入转换后的类的 Java 类开始显示：error: cannot find symbol class Chat。下面是原始类、转换后的类和日志：

原始 Java 类：

package br.com.gogame.model;

import com.google.gson.Gson;
import com.orm.SugarRecord;
import com.orm.dsl.Ignore;

import java.io.Serializable;
import java.util.List;

import br.com.gogame.model.enums.ChatType;

/**
 * Created by edgar on 11-Apr-16.
 */
public class Chat extends SugarRecord implements Serializable {

    private String title;
    private String thumbnail;
    private ChatType chat_type;
    private long chat_id;
    private int num_of_members;
    private long user_id;
    @Ignore
    private List<Long> users;

    public Chat() {
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getThumbnail() {
        return thumbnail;
    }

    public void setThumbnail(String thumbnail) {
        this.thumbnail = thumbnail;
    }

    public ChatType getChat_type() {
        return chat_type;
    }

    public void setChat_type(ChatType chat_type) {
        this.chat_type = chat_type;
    }

    public long getChat_id() {
        return chat_id;
    }

    public void setChat_id(long chat_id) {
        this.chat_id = chat_id;
    }

    public int getNum_of_members() {
        return num_of_members;
    }

    public void setNum_of_members(int num_of_members) {
        this.num_of_members = num_of_members;
    }

    public long getUser_id() {
        return user_id;
    }

    public void setUser_id(long user_id) {
        this.user_id = user_id;
    }

    public List<Long> getUsers() {
        return users;
    }

    public void setUsers(List<Long> users) {
        this.users = users;
    }

    @Override
    public String toString() {
        Gson gson = new Gson();
        return gson.toJson(this, Chat.class);
    }
}

转换后的 Kotlin 类

package br.com.gogame.model

import com.orm.SugarRecord
import com.orm.dsl.Ignore

import java.io.Serializable

import br.com.gogame.model.enums.ChatType

/**
 * Created by edgar on 11-Apr-16.
 */
class Chat : SugarRecord(), Serializable {
    var title: String? = null
    var thumbnail: String? = null
    var chat_type: ChatType? = null
    var chat_id: Long = 0
    var num_of_members: Int = 0
    var user_id: Long = 0
    @Ignore
    var users: List<Long>? = null
}

错误日志：

C:\SIBEN\Edgar\workspace\GoGame\current\app\src\main\java\br\com\gogame\commons\infra\App.java
    Error:(8, 42) error: cannot find symbol class DaggerMainComponent
    C:\SIBEN\Edgar\workspace\GoGame\current\app\src\main\java\br\com\gogame\view\fragments\FragmentChats.java
    Error:(23, 27) error: cannot find symbol class Chat
    C:\SIBEN\Edgar\workspace\GoGame\current\app\src\main\java\br\com\gogame\communication\post_office\GCMOffice.java
    Error:(25, 27) error: cannot find symbol class Chat
    C:\SIBEN\Edgar\workspace\GoGame\current\app\src\main\java\br\com\gogame\controller\util\JSONParser.java
    Error:(22, 27) error: cannot find symbol class Chat
    Error:(98, 17) error: cannot find symbol class Chat
    Error:(111, 60) error: cannot find symbol class Chat
    C:\SIBEN\Edgar\workspace\GoGame\current\app\src\main\java\br\com\gogame\controller\ChatController.java
    Error:(23, 27) error: cannot find symbol class Chat
    Error:(41, 12) error: cannot find symbol class Chat
    Error:(46, 12) error: cannot find symbol class Chat
    Error:(62, 32) error: cannot find symbol class Chat
    C:\SIBEN\Edgar\workspace\GoGame\current\app\src\main\java\br\com\gogame\commons\util\FakeDataProvider.java
    Error:(7, 27) error: cannot find symbol class Badge
    Error:(8, 27) error: cannot find symbol class Chat
    Error:(21, 24) error: cannot find symbol class Badge
    Error:(94, 24) error: cannot find symbol class Chat
    Error:(106, 20) error: cannot find symbol class Chat
    Error:(118, 20) error: cannot find symbol class Chat
    Error:(130, 20) error: cannot find symbol class Chat
    Error:(142, 20) error: cannot find symbol class Chat
    C:\SIBEN\Edgar\workspace\GoGame\current\app\src\main\java\br\com\gogame\controller\util\NotificationFactory.java
    Error:(19, 27) error: cannot find symbol class Chat
    C:\SIBEN\Edgar\workspace\GoGame\current\app\src\main\java\br\com\gogame\model\dao\ChatDAO.java
    Error:(13, 27) error: cannot find symbol class Chat
    Error:(24, 29) error: cannot find symbol class Chat
    Error:(46, 19) error: cannot find symbol class Chat
    Error:(60, 19) error: cannot find symbol class Chat
    C:\SIBEN\Edgar\workspace\GoGame\current\app\src\main\java\br\com\gogame\model\dao\ChatUserDAO.java
    Error:(7, 27) error: cannot find symbol class Chat
    C:\SIBEN\Edgar\workspace\GoGame\current\app\src\main\java\br\com\gogame\model\dao\Datamanager.java
    Error:(9, 27) error: cannot find symbol class Chat
    C:\SIBEN\Edgar\workspace\GoGame\current\app\src\main\java\br\com\gogame\model\dao\LocalUserDAO.java
    Error:(8, 27) error: cannot find symbol class Chat
    Error:(145, 24) error: cannot find symbol class Chat
    C:\SIBEN\Edgar\workspace\GoGame\current\app\src\main\java\br\com\gogame\view\adapters\BadgesAdapter.java
    Error:(15, 27) error: cannot find symbol class Badge
    Error:(21, 52) error: cannot find symbol class Badge
    Error:(25, 60) error: cannot find symbol class Badge
    C:\SIBEN\Edgar\workspace\GoGame\current\app\src\main\java\br\com\gogame\controller\FriendshipController.java
    Error:(21, 27) error: cannot find symbol class Chat
    Error:(195, 79) error: cannot find symbol class Chat
    Error:(33, 8) error: dagger.internal.codegen.ComponentProcessor was unable to process this class because not all of its dependencies could be resolved. Check for compilation errors or a circular dependency with generated code.
    C:\SIBEN\Edgar\workspace\GoGame\current\app\src\main\java\br\com\gogame\controller\MessageController.java
    Error:(23, 27) error: cannot find symbol class Chat
    Error:(91, 50) error: cannot find symbol class Chat
    Error:(117, 61) error: cannot find symbol class Chat
    Error:(128, 65) error: cannot find symbol class Chat
    Error:(216, 46) error: cannot find symbol class Chat
    Error:(34, 8) error: dagger.internal.codegen.ComponentProcessor was unable to process this class because not all of its dependencies could be resolved. Check for compilation errors or a circular dependency with generated code.
    C:\SIBEN\Edgar\workspace\GoGame\current\app\src\main\java\br\com\gogame\view\activities\ActivityCanvas.java
    Error:(38, 27) error: cannot find symbol class Chat
    Error:(64, 13) error: cannot find symbol class Chat
    Error:(53, 8) error: dagger.internal.codegen.ComponentProcessor was unable to process this class because not all of its dependencies could be resolved. Check for compilation errors or a circular dependency with generated code.
    C:\SIBEN\Edgar\workspace\GoGame\current\app\src\main\java\br\com\gogame\view\activities\ActivityFriends.java
    Error:(22, 27) error: cannot find symbol class Chat
    Error:(196, 13) error: cannot find symbol class Chat
    Error:(39, 8) error: dagger.internal.codegen.ComponentProcessor was unable to process this class because not all of its dependencies could be resolved. Check for compilation errors or a circular dependency with generated code.
    C:\SIBEN\Edgar\workspace\GoGame\current\app\src\main\java\br\com\gogame\view\adapters\ChatAdapter.java
    Error:(26, 27) error: cannot find symbol class Chat
    Error:(35, 50) error: cannot find symbol class Chat
    Error:(43, 58) error: cannot find symbol class Chat
    Error:(35, 8) error: dagger.internal.codegen.ComponentProcessor was unable to process this class because not all of its dependencies could be resolved. Check for compilation errors or a circular dependency with generated code.
    C:\SIBEN\Edgar\workspace\GoGame\current\app\src\main\java\br\com\gogame\commons\infra\dagger\MainComponent.java
    Error:(42, 8) error: dagger.internal.codegen.ComponentProcessor was unable to process this interface because not all of its dependencies could be resolved. Check for compilation errors or a circular dependency with generated code.
    Error:Execution failed for task ':app:compileDebugJavaWithJavac'.
    > Compilation failed; see the compiler error output for details.
    Information:BUILD FAILED
    Information:Total time: 7.406 secs
    Information:51 errors
    Information:4 warnings
    Information:See complete output in console

【问题讨论】：

看起来你的 kotlin 代码在构建过程中没有被编译。您是否按照tutorial 的建议应用了所需的插件？也看看这个example
就是这样！我添加了apply plugin: 'kotlin-android'，现在.kt 文件已编译并识别。非常感谢。
@EdgarDaSilvaFernandes 您应该为这个问题添加一个答案，解释您为修复它所做的工作，并将其标记为已接受的答案:)

标签： android kotlin

【解决方案1】：

我遇到了同样的问题并修复如下（假设添加了apply plugin: kotlin-android，但问题仍然存在）：

Add sourceSets under android

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

【讨论】：

【解决方案2】：

正如用户 @Ilya 所指出的，问题是 .kt 文件没有被编译，因此当我尝试在设备中部署应用程序时无法识别。为了解决这个问题，我所要做的就是在我的模块的 gradle.build 中添加apply plugin: 'kotlin-android'，如他在评论中指出的链接所示，仅此而已！现在可以了！

【讨论】：