Android studio更新到2.2之后出现的问题

更新完AS之后去写作业，发现怎么弄都是没法运行，提示的错误是Conflict with dependency 'com.android.support:support-annotations'. Resolved versions for app (22.2.1) and test app (23.1.1) differ. See http://g.co/androidstudio/app-test-app-conflict for details.

大致意思就是说你测试版本用的库和最终用的库版本号不一致

打开后面给的链接发现真的是什么都没说啊！百度了半天没有找到什么中文资料，只能看看国外的网站有什么相关的解决方法。

折腾了好久大概总结出来问题在哪里了。写下来帮大家解决这个问题。

首先先定位问题出现在哪里，build.gradle里面的dependencies里面

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:appcompat-v7:22.2.1'
    compile 'com.android.support.constraint:constraint-layout:1.0.0-alpha1'
    testCompile 'junit:junit:4.12'
    androidTestCompile 'com.android.support.test.espresso:espresso-core:2.2.2'
    androidTestCompile 'com.android.support.test:runner:0.5'
    androidTestCompile 'com.android.support:support-annotations:23.1.1'
}

一眼瞅过去肯定以为只要把最后一项

com.android.support:support-annotations:23.1.1

后面修改为22.2.1就行了是吧？naive。

我这么试了发现根本就不行。查了好久才发现并不只是这一句有问题，在google之后http://stackoverflow.com/questions/28999124/resolved-versions-for-app-22-0-0-and-test-app-21-0-3-differ给出了一些解释。

Looks like it's espresso-contrib

+--- com.android.support.test:testing-support-lib:0.1 (*)
\--- com.android.support.test.espresso:espresso-contrib:2.0
     +--- com.android.support:recyclerview-v7:21.0.3
     |    +--- com.android.support:support-annotations:21.0.3
     |    \--- com.android.support:support-v4:21.0.3
     |         \--- com.android.support:support-annotations:21.0.3
     +--- com.android.support:support-v4:21.0.3 (*)
     \--- com.android.support.test.espresso:espresso-core:2.0 (*)

参考过后就知道了，就是说下面的androidTestCompile项目中，espresso那一项当中还有包含23.1.1的引用，你要是把androidTestCompile那几条都注释了再运行就发现编译通过了。。。

下面有人回答说Actually it's a bug of new update version of Espresso Contrib

好吧，有幸遇到这种存在在环境中的bug了，给出的解决方法简单粗暴，添加force强制指定annotations

configurations.all {
    resolutionStrategy.force 'com.android.support:support-annotations:22.1.0'
}

把这一项添加到dependencies里面就可以了。再去试一试

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:appcompat-v7:22.2.1'
    compile 'com.android.support.constraint:constraint-layout:1.0.0-alpha1'
    testCompile 'junit:junit:4.12'
    androidTestCompile 'com.android.support.test.espresso:espresso-core:2.2.2'
    androidTestCompile 'com.android.support.test:runner:0.5'
    androidTestCompile 'com.android.support:support-annotations:22.2.1'
    configurations.all {
        resolutionStrategy.force 'com.android.support:support-annotations:22.1.0'
    }
}

终于build successful