试图在Android上运行嵌入式Ktor HTTP服务器

Question

我正在尝试将Ktor嵌入到Android服务中，以便在某个时候远程检查应用程序上的一些资产。

我遵循这个教程中的代码

当我试图访问链接(例如，在“192.168.2.105:7070”上)时，我会得到这个错误：

04-20 14:50:58.523 29389-29389 E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.mypackage.fetchingservice, PID: 29389
    java.lang.NoClassDefFoundError:io.ktor.application.ApplicationEvents$subscribe$1
        at io.ktor.application.ApplicationEvents.subscribe(ApplicationEvents.kt:18)
        at io.ktor.server.engine.BaseApplicationEngine.<init>(BaseApplicationEngine.kt:29)
        at io.ktor.server.engine.BaseApplicationEngine.<init>(BaseApplicationEngine.kt:15)
        at io.ktor.server.netty.NettyApplicationEngine.<init>(NettyApplicationEngine.kt:16)
        at io.ktor.server.netty.Netty.create(Embedded.kt:10)
        at io.ktor.server.netty.Netty.create(Embedded.kt:8)
        at io.ktor.server.engine.EmbeddedServerKt.embeddedServer(EmbeddedServer.kt:50)
        at io.ktor.server.engine.EmbeddedServerKt.embeddedServer(EmbeddedServer.kt:40)
        at io.ktor.server.engine.EmbeddedServerKt.embeddedServer$default(EmbeddedServer.kt:27)
        at com.hirschandmann.magickservice.KtorFetchService.onCreate(KtorFetchService.kt:30)
        at android.app.ActivityThread.handleCreateService(ActivityThread.java:2761)
        at android.app.ActivityThread.access$1800(ActivityThread.java:151)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1386)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5254)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:935)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:730)

这是密码。服务在清单中注册，我使用：adb shell am startservice com.mypackage.service/.KtorFetchService从亚行启动它。

class KtorFetchService : Service() {
    override fun onBind(intent: Intent?): IBinder {
    TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
    }
    private val HTTP_PORT = 7070
    override fun onCreate() {
        embeddedServer(Netty, HTTP_PORT) {
            routing {
                get("/") {
                    call.respondText("My Example Fetch", ContentType.Text.Html)
                }
            }
        }.start(wait = true)
        super.onCreate()
    }
}

下面是模块gradle文件：

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

android {
    compileSdkVersion 27
    defaultConfig {
        applicationId "com.hirschandmann.magickservice"
        minSdkVersion 21
        targetSdkVersion 27
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }

    packagingOptions {
        pickFirst 'META-INF/*'
    }
}

repositories {
    jcenter()
    mavenCentral()
    maven { url "http://dl.bintray.com/kotlin/ktor" }
    maven { url "https://dl.bintray.com/kotlin/kotlinx" }
}

configurations {
    ktlint
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation"org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
    implementation'com.android.support:appcompat-v7:27.1.1'
    testImplementation'junit:junit:4.12'
    androidTestImplementation'com.android.support.test:runner:1.0.1'
    androidTestImplementation'com.android.support.test.espresso:espresso-core:3.0.1'

    // AutoValue
    compileOnly "com.google.auto.value:auto-value:1.5.2"
    annotationProcessor "com.google.auto.value:auto-value:1.5.2"

    // ktlint
    ktlint "com.github.shyiko:ktlint:0.15.0"

    implementation'com.github.hkk595:Resizer:v1.5'
    implementation'com.jrummyapps:android-shell:1.0.1'
    implementation'org.nanohttpd:nanohttpd:2.3.1'
    implementation"io.ktor:ktor:$ktor_version" // ktor dependency
    implementation"io.ktor:ktor-server-netty:$ktor_version"

}
task ktlint(type: JavaExec, group: "verification") {
    description = "Check Kotlin code style."
    classpath = configurations.ktlint
    main = "com.github.shyiko.ktlint.Main"
    args "src/**/*.kt"
    //args "--reporter=checkstyle,output=${buildDir}/ktlint.xml"
}
check.dependsOn ktlint

androidExtensions {
    experimental = true
}

下面是该项目的gradle文件：

buildscript {
    ext.kotlin_version = '1.2.40'
    ext.ktor_version = '0.9.1'

    repositories {
        google()
        jcenter()
        mavenCentral()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.1.1'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

plugins {
    id "io.gitlab.arturbosch.detekt" version "1.0.0.RC6-3"
}

allprojects {
    repositories {
        google()
        jcenter()
        maven { url 'https://jitpack.io' }
    }
}

detekt {
    version = "1.0.0.RC6-3"
    profile("main") {
        input = "$projectDir/app/src/main/java"
        config = "$projectDir/default-detekt-config.yml"
        filters = ".*test.*,.*/resources/.*,.*/tmp/.*"
    }
}

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

该设备是带有Android5.1.1 (API 22)的Odroid C2，我使用的是AndroidStudio3.1和JRE1.8，运行在MacOS 10.13.3上。

Answer 1

此错误是由ktor ApplicationEvents.kt:18中的下一行引起的。

handlers.computeIfAbsent(definition) { LockFreeLinkedListHead() }.addLast(registration)

这导致它失败，直到ConcurrentHashMap.computeIfAbsent和java.util.function.Function最初是在APILevel24 (证明)中引入的。

请注意，ktor服务器从未打算在android上运行，最初的目标是使用JDK8的服务器。

Answer 2

我已经在Android 5+上运行了一台基于Netty的Ktor服务器，我创建了这个最小的回购程序来演示它：https://github.com/gnarea/minimal-ktor-server-android。