Cannot run my app, asking to select Android SDK

Just you need to sync your project file with your gradle file.

File -> Sync Project with Gradle Files

I tried every answer in this post but my problem only got resolved when I made these steps:

File -> Close project -> Remove project -> Open existing project (same project)

Maybe this will save a morning to another person with the same bug.

EDIT

This happened to me a lot on a MacBook. After I posted this answer it just kept happening so what I did was:

• uninstall the Android Studio version I had from the App Store;
• download the desktop stable version from Android Studio website;
• start using the desktop version of Android Studio.

Never happened again.

You need to insall SDK api 19 check this out. https://developer.android.com/studio/releases/platforms

I had the same problem and what it worked for me was just sync with gradle. I just did what I've found in this similar question:

How do I "select Android SDK" in Android Studio?

The original answer:

go to build.gradle and click sync now. Then it worked.

Update :

File -> Sync Project with Gradle Files (Android Studio 3.1.1)

Tools -> Android -> Sync Project with Gradle Files (Android Studio 3.0.1) Or You can click on the icon from the toolbar.

Sync Project Icon

This answer may not help works for later version as Android studio Team work on making the tool more better, the way to sync may be

different in the next version of Android Studio.

COMMON WAY that may helps is try to sync project and then Invalidate Caches and Restart Android Studio.

Solution for Android Studio 3.1.2

Before that, by the way, I had invalidated cache and restarted too, but it didn't work. Please, try and let us know.

P.S. I had this problem after I imported a project from Git, just in case someone would like to replicate.

Just click on the button ..."Sync Project with gradle file" Error will be remove