遇到的错误1：

Error:FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':app:preDebugAndroidTestBuild'.
> Conflict with dependency 'com.android.support:support-annotations' in project ':app'. Resolved versions for app (27.0.2) and test app (27.1.1) differ. See https://d.android.com/r/tools/test-apk-dependency-conflicts.html for details.

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

BUILD FAILED in 1s

解决办法：

在app下的gradle中添加如下：

android {
.....
}

configurations.all {
    resolutionStrategy.force 'com.android.support:support-annotations:27.1.1'
}

dependencies {
.....
}

遇到问题2：

Error:FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':app:transformResourcesWithMergeJavaResForDebug'.
> More than one file was found with OS independent path 'META-INF/rxjava.properties'

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

BUILD FAILED in 5s

解决办法：

在app下的gradle中添加如下：

android {
//添加这个packagingOptions{
    exclude 'META-INF/rxjava.properties'
}}

记录一下