将现有Android Java项目迁移至KMM后出现大量未解析引用错误求助

要把现有Android应用通过Kotlin Multiplatform（KMM）适配iOS，完全零基础。创建shared模块并调整build配置后项目能构建，但把AndroidApp模块的Java文件移到shared模块转成Kotlin后，所有Android相关导入和代码都报未解析引用错误，比如android.content.Intent、FirebaseInstanceId、getApplicationContext()等都识别不了。

转换后的Kotlin代码 #

package eu.tinysolutions.tinyprocas

import android.content.Intent
import android.util.Log
import com.google.firebase.iid.FirebaseInstanceId
import com.google.firebase.iid.FirebaseInstanceIdService


class FbInstanceIdService : FirebaseInstanceIdService() {
    fun onTokenRefresh() {
        // Get updated InstanceID token.
        val refreshedToken: String = FirebaseInstanceId.getInstance().getToken()
        android.util.Log.d(
            TAG,
            "Refreshed token: $refreshedToken"
        )

        // If you want to send messages to this application instance or
        // manage this apps subscriptions on the server side, send the
        // Instance ID token to your app server.
        getApplicationContext().sendBroadcast(Intent(TOKEN_BROADCAST))
        storeToken(refreshedToken)
    }

    private fun storeToken(token: String) {
        SharedPreferencesManager.getInstance(getApplicationContext()).storeFirebaseToken(token)
    }

    companion object {
        const val TAG = "FirebaseID"
        const val TOKEN_BROADCAST = "tokenbroadcast"
    }
}

报错信息 #

• Unresolved reference: content
• Unresolved reference: util
• Unresolved reference: FirebaseInstanceId
• Unresolved reference: FirebaseInstanceIdService
• Unresolved reference: getApplicationContext

项目级build.gradle文件 #

// Top-level build file where you can add configuration options common to all sub-projects/modules.

buildscript {
    
    repositories {
        google()
        jcenter()
        mavenCentral()
    }
    dependencies {
        classpath('com.android.tools.build:gradle:8.1.4')
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:1.9.0"

        classpath 'com.google.gms:google-services:4.4.1'
    }
}

plugins {
    // Declare the Kotlin Multiplatform plugin with a specific version and set apply false
    id 'org.jetbrains.kotlin.multiplatform' version '1.9.0' apply false
    id 'com.android.application' version '8.1.4' apply false
    id 'com.android.library' version '8.1.4' apply false
    id("com.google.gms.google-services") version "4.4.1" apply false

}

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

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

androidApp模块build.gradle文件 #

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

android {
    compileSdk 27
    defaultConfig {
        applicationId "changedID"
        minSdkVersion 26
        targetSdkVersion 27
        versionCode 11
        versionName "1.11"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    applicationVariants.all { variant ->
        variant.resValue "string", "versionName", variant.versionName
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
    namespace 'changedNamespace'
}

repositories {
    maven { url 'https://jitpack.io' }
}

dependencies {
    implementation fileTree(include: ['*.jar'], dir: 'libs')
    implementation 'com.android.support:appcompat-v7:27.1.1'
    implementation 'com.android.support.constraint:constraint-layout:1.1.1'
    implementation 'com.android.support:support-v4:27.1.1'
    implementation 'com.google.firebase:firebase-messaging:11.8.0'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
    implementation 'com.android.support:support-v4:27.1.1'
    implementation 'com.android.support:design:27.1.1'
    implementation 'com.android.volley:volley:1.1.0'
    implementation 'com.ms-square:expandableTextView:0.1.4'
    implementation project(':shared')
    implementation 'com.github.PhilJay:MPAndroidChart:v3.0.3'
}

apply plugin: 'com.google.gms.google-services'

shared模块build.gradle.kts文件 #

plugins {
    //alias(libs.plugins.kotlinMultiplatform)
    //alias(libs.plugins.androidLibrary)
    //alias(libs.plugins.androidApplication)
    id("org.jetbrains.kotlin.multiplatform")
    id("com.android.application")
    id("com.google.gms.google-services")
}

repositories {
    maven(url = "https://jitpack.io")
}


kotlin {
    androidTarget {
        compilations.all {
            kotlinOptions {
                jvmTarget = "1.8"
            }
        }
    }
    
    listOf(
        iosX64(),
        iosArm64(),
        iosSimulatorArm64()
    ).forEach {
        it.binaries.framework {
            baseName = "shared"
            isStatic = true
        }
    }

    sourceSets {
        val commonMain by getting {
            dependencies {
                implementation(fileTree(mapOf("dir" to "libs", "include" to listOf("*.jar"))))
                implementation(project(":shared"))
                implementation ("com.android.support:appcompat-v7:27.1.1")
                implementation ("com.android.support.constraint:constraint-layout:1.1.1")
                implementation ("com.android.support:support-v4:27.1.1")
                implementation ("com.google.firebase:firebase-messaging:11.8.0")
                implementation ("com.android.support:support-v4:27.1.1")
                implementation ("com.android.support:design:27.1.1")
                implementation ("com.android.volley:volley:1.1.0")
                implementation ("com.ms-square:expandableTextView:0.1.4")
                implementation ("com.github.PhilJay:MPAndroidChart:v3.0.3")
            }
        }
        val androidMain by getting{
            dependencies{
                implementation(fileTree(mapOf("dir" to "libs", "include" to listOf("*.jar"))))
                implementation(project(":shared"))
                implementation ("com.android.support:appcompat-v7:27.1.1")
                implementation ("com.android.support.constraint:constraint-layout:1.1.1")
                implementation ("com.android.support:support-v4:27.1.1")
                implementation ("com.google.firebase:firebase-messaging:11.8.0")
                implementation ("com.android.support:support-v4:27.1.1")
                implementation ("com.android.support:design:27.1.1")
                implementation ("com.android.volley:volley:1.1.0")
                implementation ("com.ms-square:expandableTextView:0.1.4")
                implementation ("com.github.PhilJay:MPAndroidChart:v3.0.3")
            }
        }
        val commonTest by getting {
            dependencies {
                implementation(kotlin("test-common"))
                implementation(kotlin("test-annotations-common"))
            }
        }

        // Specific platform configurations
        val iosX64Main by getting {
            dependsOn(commonMain)
        }
        val iosArm64Main by getting {
            dependsOn(commonMain)
        }
        val iosSimulatorArm64Main by getting {
            dependsOn(commonMain)
        }
    }
}

android {
    namespace = "changedNamespace"
    compileSdk = 27
    defaultConfig {
        minSdk = 26
        applicationId = "changedID"
        versionCode = 11
        versionName = "1.11"
        targetSdk = 27
    }
}

1. 修正shared模块的插件配置 #

shared模块是KMM跨平台库，不能用com.android.application插件，替换为com.android.library。修改shared模块build.gradle.kts的plugins块：

plugins {
    id("org.jetbrains.kotlin.multiplatform")
    id("com.android.library") // 替换原com.android.application
    id("com.google.gms.google-services")
}

同时删除android块中的applicationId（library模块无需该配置）：

android {
    namespace = "changedNamespace"
    compileSdk = 27
    defaultConfig {
        minSdk = 26
        // 移除applicationId = "changedID"
        versionCode = 11
        versionName = "1.11"
        targetSdk = 27
    }
}

2. 调整代码存放位置 #

FbInstanceIdService是Android平台专属代码（依赖Android SDK和Firebase Android库），必须从commonMain目录移到shared/src/androidMain/kotlin/[你的包名]目录下。

3. 精简依赖配置 #

• 移除commonMain中所有Android专属依赖（如com.android.support、com.google.firebase:firebase-messaging等），这些依赖只保留在androidMain中。
• 删除implementation(project(":shared"))，避免循环依赖。
• 精简后的sourceSets配置：

sourceSets {
    val commonMain by getting {
        dependencies {
            // 仅保留跨平台通用依赖，如kotlin标准库
        }
    }
    val androidMain by getting{
        dependencies{
            implementation(fileTree(mapOf("dir" to "libs", "include" to listOf("*.jar"))))
            implementation("com.android.support:appcompat-v7:27.1.1")
            implementation("com.android.support.constraint:constraint-layout:1.1.1")
            implementation("com.android.support:support-v4:27.1.1")
            implementation("com.google.firebase:firebase-messaging:11.8.0")
            implementation("com.android.support:design:27.1.1")
            implementation("com.android.volley:volley:1.1.0")
            implementation("com.ms-square:expandableTextView:0.1.4")
            implementation("com.github.PhilJay:MPAndroidChart:v3.0.3")
        }
    }
    val commonTest by getting {
        dependencies {
            implementation(kotlin("test-common"))
            implementation(kotlin("test-annotations-common"))
        }
    }

    // iOS相关sourceSet默认依赖commonMain，无需手动声明dependsOn
    val iosX64Main by getting
    val iosArm64Main by getting
    val iosSimulatorArm64Main by getting
}

4. 修正Kotlin代码问题 #

• onTokenRefresh是重写父类方法，必须添加override关键字。
• 移除冗余的android.util.Log调用，直接使用导入的Log。
  修正后的代码：

package eu.tinysolutions.tinyprocas

import android.content.Intent
import android.util.Log
import com.google.firebase.iid.FirebaseInstanceId
import com.google.firebase.iid.FirebaseInstanceIdService


class FbInstanceIdService : FirebaseInstanceIdService() {
    override fun onTokenRefresh() {
        val refreshedToken: String = FirebaseInstanceId.getInstance().getToken()
        Log.d(TAG, "Refreshed token: $refreshedToken")

        getApplicationContext().sendBroadcast(Intent(TOKEN_BROADCAST))
        storeToken(refreshedToken)
    }

    private fun storeToken(token: String) {
        SharedPreferencesManager.getInstance(getApplicationContext()).storeFirebaseToken(token)
    }

    companion object {
        const val TAG = "FirebaseID"
        const val TOKEN_BROADCAST = "tokenbroadcast"
    }
}

5. 同步并重构项目 #

点击Android Studio的Sync Project with Gradle Files按钮，执行Clean Project和Rebuild Project，错误即可解决。

内容的提问来源于stack exchange，提问作者cheese