AndroidStudio报错Resolved versions for app (26.1.0) and test app (27.1.1) differ.

新建一个Project发现直接报错：

Error:Execution failed for task ':app:preDebugAndroidTestBuild'.
> Conflict with dependency 'com.android.support:support-annotations' in project ':app'. Resolved versions for app (26.1.0) and test app (27.1.1) differ. See https://d.android.com/r/tools/test-apk-dependency-conflicts.html for details.

build.gradle全貌：

究其原因和解决方案：

三种方法：

1.注释dependecies中androidTestImplementation中的代码：

    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'

2.在dependecies中添加如下代码：

 configurations.all {
        resolutionStrategy.force 'com.android.support:support-annotations:26.1.0'
    }

3.改下complieSdkVersion和v7版本到27和27.1.1