现在在Android Studio 3及以上，你可以尝试同步项目与gradle如下:

File -> Sync Project with Gradle Files

它帮助了我:

1. close project
2. remove .idea/ folder
3. select "import project (Gradle, Eclipse ADT, etc.)"

环境:

Android Studio 3.1.3
OS Macos High Sierra 10.13.5

另一个答案不适合我。

buildToolsVersion可能在应用程序的build.gradle中丢失

buildToolsVersion "26.0.3"

像这样加起来

Source Compatibility should be selected as the minimum Android Version that your app should be compatible with(usually selected as SDK 15), Target Compatibility should be selected as the newest Android Version that your app should be compatible with(SDK 23). Afterwards you want to check your AndroidMenifest and your gradle.build to see if its realy set to the properties selected if not you can just add it manually. and ofcourse you should check the SDK Location is actually pointing to your android studio SDK folder (if you are importing from Eclipse then you should point to your Eclipse SDK folder).

点击这个图标来同步gradle

或者编辑你的gradle模块，然后同步

同步没帮到我。这两种方法都不能使缓存失效。 我只是简单地删除并再次克隆存储库，它工作:

确保没有未提交的更改 将本地存储库与远程github同步 删除带有本地存储库的文件夹 再次将存储库从github克隆到本地 在Android Studio中打开克隆的存储库 重新构建并运行它。