如果你的android SDK路径是给定的，但你仍然面临这个问题，那么这可能是因为你的android工作室没有很好地同步，即使你点击了“立即同步”链接。

为了重新同步，去到app gradle文件，做些改变，或者给一个空间，然后再同步。它会完美工作的。

遵循以下步骤:

转到Android Studio设置 使用搜索栏搜索“Android SDK” 确保android sdk文件夹的路径是正确的。 在此之后，还要确保路径在项目(local.properties)文件中的提示符后自动更新。如果没有，请手动操作。

希望这能有所帮助。

我的问题通过在Android Studio中设置NDK路径解决了。

文件->项目结构->NDK位置。

点击Android Studio中gradle垂直标签的第一个刷新按钮

点击这个图标来同步gradle

或者编辑你的gradle模块，然后同步

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.