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

buildToolsVersion "26.0.3"

像这样加起来

在Android Studio 3及以上版本中，适用于Windows、Mac和Linux:

File -> Sync Project with Gradle Files

解决了!

或者你可以通过快捷键来完成:

按⌘+ Shift + A (Mac)或Ctrl + Shift + A (Windows, Linux)。然后弹出编辑文本并写入“同步项目与Gradle文件”。然后双击该选项。

你的问题解决了!它会同步你的gradle文件和你的项目文件。

截图:

点击Android Studio中gradle垂直标签的第一个刷新按钮

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

对于Android Studio 3.5，“File -> Sync project with gradle files”就足够了。

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).