AS编译出现 ':app:preDebugAndroidTestBuild'的错误解决办法

打开Android studio 在build过程中总会出现以下错误

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.

在app下的build.gradle文件中的dependences { }中添加如下代码：

androidTestCompile('com.android.support:support-annotations:26.1.0')
 {
   force = true
 }

例如：

dependencies {
    androidTestCompile('com.android.support:support-annotations:26.1.0') {
        force = true
    }
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:26.1.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.2'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}