can't resolve AppCompatActivity

Okay, to anybody who might stumble upon this now, Android Studio is very, very, very weird.

Solution : Go to your build.gradle file and in your dependencies find the appcompat one, something like compile 'com.android.support:appcompat-v7:XX.X.X'

Change it to compile 'com.android.support:appcompat-v7:XX.X.+'

Then click on Sync Now on the top right of the editor. All the red squiggly lines should go if everything else in your code is correct.

Then go back to your build.gradle and change it back to whatever it was and click Sync Now

It should all be fine given that you have the latest version of everything or close to it.

Lets get going step by step:first clean project by using

Build->Clean

if this doesn't helps then use your second weapon

File>Invalidate Caches/Restart...

But the real problem begins when all the above options doesn't worksso use your ultimate weapon close project and go to project location directory and delete

.idea

You can open your project now again. This worked for me and problem comes most often when you are working with VCS. And this problem is not associated with android component classes but also to the libraries, both shows the same error.

I was having the same issue, but when I did Invalidate cache/restart option it worked fine for me.

First try to clear all your build files

Build->Clean

if it doesn't work try this option

File -> Invalidate cache/Restart