只需将构建工具版本更改为25.0.3..现在开始同步 我希望它会有所帮助。

在Mac上按“⌘+Shift+A”(在Windows上按“Ctrl+Shift+A”)，并在弹出的EditText中写入“将项目与Gradle文件同步”。然后双击出现的选项。然后它将同步您的Gradle文件SDK与项目文件。

Work for me 1文件>关闭投影。2打开一个现有的Android Studio项目

从android工作室点击File菜单。

文件->设置->系统设置-> Android SDK

按“Ctrl+shift+A”并在弹出的EditText中写入“Sync Project with Gradle Files”。然后双击出现的选项。然后它将同步您的Gradle文件SDK与项目文件。

After opening my project in Android Studio, I opened the App version of the build.gradle file, located in the Gradle Scripts folder of the Project. When I hovered my mouse pointer over the buildToolsVersion number, a tooltip popped, indicating that the version of Android Build Tools needed to be upgraded (see screenshot). I changed the value of the buildToolsVersion to the one identified by the error (27.0.2) and the problem was solved. The original error (Please select Android SDK) went away and the project compiled successfully, again. Although this solution was mentioned previously, the exact steps seemed to be missing, so hopefully this clears up any doubt. I guess the root cause for this problem is that a new version of the build tools were released but Android Studio did not trigger any notification to me, which would have indicated that I should manually fix this (since Android Studio does not seeem to have the ability to upgrade this build.gradle file internally), which leaves the onus on the user to find the problem and fix it.