尝试将 Android 组件放入库时出现 ClassNotFoundException

Question

我有两个 Android 项目：一个应用程序和一个库。该库使用 StreamProvider 并作为 AAR 模块包含在应用程序项目中。以下是两个项目中的重要内容（由我更改）：

库项目：

AndroidManifest.xml:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="au.com.a1ict.mylib">
...
<provider
    android:name=".provider.StreamProvider"
    android:authorities="${applicationId}.provider"
    android:exported="false"
    android:grantUriPermissions="true">
    <meta-data
        android:name="com.commonsware.cwac.provider.STREAM_PROVIDER_PATHS"
        android:resource="@xml/file_paths"/>
</provider>

build.gradle:

repositories {
    maven {
        url "https://s3.amazonaws.com/repo.commonsware.com"
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:appcompat-v7:24.2.0'
    compile 'com.commonsware.cwac:provider:0.4.3'
}

provider/StreamProvider.java:

package au.com.a1ict.mylib.provider;

public class StreamProvider extends com.commonsware.cwac.provider.StreamProvider {
    public StreamProvider() {
    }
}

应用项目：

AndroidManifest.xml:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="au.com.a1ict.myapplication">

app/build.gradle:

dependencies {
    compile fileTree(include: ['*.jar'], dir: 'libs')
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:24.2.0'
    compile project(':app-debug')
}

app-debug/build.gradle：（Android Studio 在导入库时选择的名称）：

configurations.maybeCreate("default")
artifacts.add("default", file('app-debug.aar'))

settings.gradle:

include ':app', ':app-debug'

编译和链接阶段顺利结束，就在应用程序即将启动时，我在日志中看到：

08-31 13:16:30.386 6656-6656/au.com.a1ict.myapplication E/AndroidRuntime: FATAL EXCEPTION: main
Process: au.com.a1ict.myapplication, PID: 6656
java.lang.RuntimeException: Unable to get provider au.com.a1ict.mylib.provider.StreamProvider: java.lang.ClassNotFoundException: Didn't find class "au.com.a1ict.mylib.provider.StreamProvider" on path: DexPathList[[zip file "/data/app/au.com.a1ict.myapplication-1/base.apk"],nativeLibraryDirectories=[/vendor/lib64, /system/lib64]]
at android.app.ActivityThread.installProvider(ActivityThread.java:5002)
at android.app.ActivityThread.installContentProviders(ActivityThread.java:4594)
at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4534)
at android.app.ActivityThread.access00(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1364)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.ClassNotFoundException: Didn't find class "au.com.a1ict.mylib.provider.StreamProvider" on path: DexPathList[[zip file "/data/app/au.com.a1ict.myapplication-1/base.apk"],nativeLibraryDirectories=[/vendor/lib64, /system/lib64]]
at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56)
at java.lang.ClassLoader.loadClass(ClassLoader.java:511)
at java.lang.ClassLoader.loadClass(ClassLoader.java:469)
at android.app.ActivityThread.installProvider(ActivityThread.java:4987)
at android.app.ActivityThread.installContentProviders(ActivityThread.java:4594) 
at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4534) 
at android.app.ActivityThread.access00(ActivityThread.java:151) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1364) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:135) 
at android.app.ActivityThread.main(ActivityThread.java:5254) 
at java.lang.reflect.Method.invoke(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:372) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698) 
Suppressed: java.lang.ClassNotFoundException: Didn't find class "au.com.a1ict.mylib.provider.StreamProvider" on path: DexPathList[[dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-support-annotations-24.2.0_789c261ae08b7fa204bc7699aff21c5cfe4ba218-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-slice_9-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-slice_8-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-slice_7-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-slice_6-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-slice_5-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-slice_4-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-slice_3-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-slice_2-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-slice_1-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-slice_0-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-internal_impl-24.2.0_e6a045dc4d6d599e73e736c6e39e0dcf8f4490fd-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-internal_impl-24.2.0_c96bb2006cae6009a151f1c7452e4a28bb4585dd-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-internal_impl-24.2.0_a0d684a27f515a3bfd5243a957fad78a92e4fbcd-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-internal_impl-24.2.0_369ab9945f1de9068baf3d6bc7fa4d034f59c368-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-internal_impl-24.2.0_2f9cbd5b7b19dc2598fd196e294d333d451c7a47-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-com.android.support-support-vector-drawable-24.2.0_ec6f782152c4bb5e3b0b6840a634e809e68482eb-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-com.android.support-support-v4-24.2.0_3e07c7a20cb62485a70
08-31 13:16:30.426 6656-6656/au.com.a1ict.myapplication D/Error: ERR: exClass=java.lang.ClassNotFoundException
08-31 13:16:30.426 6656-6656/au.com.a1ict.myapplication D/Error: ERR: exMsg=Didn't find class "au.com.a1ict.mylib.provider.StreamProvider" on path: DexPathList[[zip file "/data/app/au.com.a1ict.myapplication-1/base.apk"],nativeLibraryDirectories=[/vendor/lib64, /system/lib64]]
08-31 13:16:30.426 6656-6656/au.com.a1ict.myapplication D/Error: ERR: file=BaseDexClassLoader.java
08-31 13:16:30.426 6656-6656/au.com.a1ict.myapplication D/Error: ERR: class=dalvik.system.BaseDexClassLoader
08-31 13:16:30.426 6656-6656/au.com.a1ict.myapplication D/Error: ERR: method=findClass line=56
08-31 13:16:30.426 6656-6656/au.com.a1ict.myapplication D/Error: ERR: stack=java.lang.RuntimeException: Unable to get provider au.com.a1ict.mylib.provider.StreamProvider: java.lang.ClassNotFoundException: Didn't find class "au.com.a1ict.mylib.provider.StreamProvider" on path: DexPathList[[zip file "/data/app/au.com.a1ict.myapplication-1/base.apk"],nativeLibraryDirectories=[/vendor/lib64, /system/lib64]]
at android.app.ActivityThread.installProvider(ActivityThread.java:5002)
at android.app.ActivityThread.installContentProviders(ActivityThread.java:4594)
at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4534)
at android.app.ActivityThread.access00(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1364)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.ClassNotFoundException: Didn't find class "au.com.a1ict.mylib.provider.StreamProvider" on path: DexPathList[[zip file "/data/app/au.com.a1ict.myapplication-1/base.apk"],nativeLibraryDirectories=[/vendor/lib64, /system/lib64]]
at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56)
at java.lang.ClassLoader.loadClass(ClassLoader.java:511)
at java.lang.ClassLoader.loadClass(ClassLoader.java:469)
at android.app.ActivityThread.installProvider(ActivityThread.java:4987)
at android.app.ActivityThread.installContentProviders(ActivityThread.java:4594) 
at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4534) 
at android.app.ActivityThread.access00(ActivityThread.java:151) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1364) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:135) 
at android.app.ActivityThread.main(ActivityThread.java:5254) 
at java.lang.reflect.Method.invoke(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:372) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698) 
Suppressed: java.lang.ClassNotFoundException: Didn't find class "au.com.a1ict.mylib.provider.StreamProvider" on path: DexPathList[[dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-support-annotations-24.2.0_789c261ae08b7fa204bc7699aff21c5cfe4ba218-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-slice_9-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-slice_8-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-slice_7-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-slice_6-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-slice_5-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-slice_4-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-slice_3-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-slice_2-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-slice_1-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-slice_0-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-internal_impl-24.2.0_e6a045dc4d6d599e73e736c6e39e0dcf8f4490fd-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-internal_impl-24.2.0_c96bb2006cae6009a151f1c7452e4a28bb4585dd-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-internal_impl-24.2.0_a0d684a27f515a3bfd5243a957fad78a92e4fbcd-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-internal_impl-24.2.0_369ab9945f1de9068baf3d6bc7fa4d034f59c368-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-internal_impl-24.2.0_2f9cbd5b7b19dc2598fd196e294d333d451c7a47-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-com.android.support-support-vector-drawable-24.2.0_ec6f782152c4bb5e3b0b6840a634e809e68482eb-classes.dex", dex file "/data/data/au.com.a1ict.myapplication/files/instant-run/dex/slice-com.android.support-support-v4-24.2.0_3e07c7a20cb62485a70a27026d0f6ed7d58d351e-classes.dex", dex file "/data/data/au.com.a1i

这一定与组件 (StreamProvider) 位于 AAR 文件中这一事实有关，因为当在一个项目中使用时，它可以完美地工作（相同的命名空间、包、... -- 我只是复制库项目的文件放入 app-debug)。相关的 SO 问题大多与 Eclipse 有关。我真的没主意了。

Answer 1

好吧，这花了一个地狱般的调查，但我终于弄明白了。它实际上是几个问题的组合：

AAR 不包含有关其依赖项的信息；所以我要么必须手动包含它们，要么设置一个 Maven 存储库。
首先我使用 maven-publish 插件只是为了意识到它不会自动填写 AAR 依赖项。
然后我用了Gradle Android Maven plugin，好多了但是：
最新的 Gradle Android Maven 插件 (1.5) 需要 Gradle 3.0+ 而 AS offers/recommends/sets 2.14.1 所以我不得不将插件降级到 1.4.1
然后我意识到实际上我仍然必须将 https://s3.amazonaws.com/repo.commonsware.com 依赖项 url 包含到应用程序项目中，因为 POM 文件不包含有关存储库的信息，仅包含包。

在那之后我终于没有看到任何崩溃。顺便说一句，我不必使用

compile ('com.group:artifact:0.0.1@aar'){transitive=true}

表单（如整个 SO 所建议的那样），将我的依赖项指定为：

compile ('com.group:artifact:0.0.1')

够了。

尝试将 Android 组件放入库时出现 ClassNotFoundException

ClassNotFoundException when trying to put Android component into a library

android

gradle

android-library