编译Android旧项目遇Parcelable接口实现报错，求解决方案

重新编译两年前可正常编译的旧Android项目时，出现两个编译错误：

• 类Device并非抽象类，未实现android.os.Parcelable中定义的抽象方法public abstract fun writeToParcel(p0: Parcel, p1: Int): Unit
• 报错writeToParcel未覆盖任何方法

相关代码 #

Device.kt #

import android.bluetooth.BluetoothDevice
import android.os.Parcel
import android.os.Parcelable

data class Device(
    val device: BluetoothDevice,
    val rssi: Int = 0): Parcelable {
    constructor(parcel: Parcel) : this(
        parcel.readParcelable(BluetoothDevice::class.java.classLoader)!!,
        parcel.readInt()
    )

    override fun describeContents() = 0

    override fun writeToParcel(dest: Parcel?, flags: Int) {
        dest?.writeParcelable(device, flags)
    }

    companion object CREATOR : Parcelable.Creator<Device> {
        override fun createFromParcel(parcel: Parcel): Device {
            return Device(parcel)
        }

        override fun newArray(size: Int): Array<Device?> {
            return arrayOfNulls(size)
        }
    }
}

模块build.gradle #

plugins {
    id 'com.android.application'
    id 'kotlin-android'
    id 'androidx.navigation.safeargs'
}

android {
    compileSdkVersion 34
    buildToolsVersion "30.0.3"

    defaultConfig {
        applicationId "com.astar.osterrig.controlrelay"
        minSdkVersion 22
        targetSdkVersion 34
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    kotlinOptions {
        jvmTarget = '1.8'
    }
    buildFeatures {
        viewBinding true
    }
    namespace 'com.astar.osterrig.controlrelay'
}

dependencies {

    implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
    implementation 'androidx.core:core-ktx:1.12.0'
    implementation 'androidx.appcompat:appcompat:1.6.1'
    implementation 'com.google.android.material:material:1.11.0'
    implementation 'androidx.fragment:fragment-ktx:1.6.2'
    implementation 'androidx.constraintlayout:constraintlayout:2.1.4'
    implementation 'androidx.navigation:navigation-fragment-ktx:2.7.6'
    implementation 'androidx.navigation:navigation-ui-ktx:2.7.6'
    implementation 'eo.view:signalstrength:2.0.0'

    implementation 'no.nordicsemi.android:ble:2.3.0'

    testImplementation 'junit:junit:4.13.2'
    androidTestImplementation 'androidx.test.ext:junit:1.1.5'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.5.1'
}

项目根目录build.gradle #

// Top-level build file where you can add configuration options common to all sub-projects/modules.
buildscript {
    ext.kotlin_version = '1.9.0'
    repositories {
        google()
        mavenCentral()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:8.2.1'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
        classpath 'androidx.navigation:navigation-safe-args-gradle-plugin:2.7.6'
        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
        google()
        mavenCentral()
        jcenter() // Warning: this repository is going to shut down soon
    }
}

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

问题核心是**writeToParcel方法的参数签名与Parcelable接口定义不匹配**：

• 新版Android SDK/Kotlin中，Parcelable接口要求的writeToParcel方法第一个参数为非空Parcel，但你的代码写成了可空的Parcel?，导致既未正确实现接口方法，又错误标记了override
• 另外代码还遗漏了rssi字段的序列化写入，会导致反序列化后该字段值异常

修改Device.kt中的writeToParcel方法即可解决：

override fun writeToParcel(dest: Parcel, flags: Int) {
    dest.writeParcelable(device, flags)
    dest.writeInt(rssi) // 补上rssi字段的序列化
}

补充说明 #

两年前项目可正常编译，是因为当时的Parcelable接口在Kotlin中的参数空安全规则更宽松，升级Gradle、Kotlin或Android SDK后，接口签名检查严格化，触发了该错误。

内容的提问来源于stack exchange，提问作者Alan Khabitsov