问题
I update my android studio to 3.1.3 but I cannot use platform 27 now when I click "install platform and sync project" it pop up a download window and then disappear. But the error still exist. SDK Platforms is following:
expand SDK:
回答1:
For anyone get this issue, you should uninstall Android SDK 27 then re-install it from SDK download manager.
回答2:
@TrongHiue's answer didn't work for me. (Mac user, Android 3.2.1).
I had to close the IDE, go to Library/Android/sdk and rename the 'sdk' folder to 'sdk2'. Then reopen Android Studio - it will prompt you to tell you it can't find the old sdk folder but will automatically use sdk2. Hit ok. Then, let Android Studio re-index. It will now find platform 27 and you should be able to launch your app.
If you want to change your sdk folder back from skd2 to sdk, close the IDE, rename back to 'sdk', re-open the IDE, update the SDK location in File -> Project Structure, and make sure local.properties is pointing to 'sdk' folder and not 'sdk2'.
回答3:
In my case, I fixed it by click "Edit" (Next to Android SDK Location) and install SDK platform at SDK Setup window.
Click here to see image
回答4:
Ran into same problem but with API 26 and (win) studio 3.5.1. XavierDominguez solution was close to what I had to do to fix it. Close IDE, renamed Sdk to Sdk2, reopened studio, problem persisted so closed IDE, renamed it back to Sdk, reopened and worked this time around. Posted in case someone ran across same problem.
回答5:
This usually happens when popup for update tools and you click on Update and after some time before finishing Update you Cancel It. Simply Go to FIle--> Invalidate Caches/Restart
来源：https://stackoverflow.com/questions/51256942/missing-android-platforms-detected-android-27