Android studio design editor is unavailable until after a successful project sync

Just sync your project with gradles. File --> Sync Project with Gradle Files

1. Build -> Clean Project

2. Build -> Rebuild Project

3. File -> Sync project with gradle files . If not worked then try

   File -> Invalidate Caches / Restart .

It's work for me !!!

That could be fixed in one or two steps, depending on how nice is Android Studio today:

1. Try to sync your project with gradle files:

2. If that doesn't work, invalidate Android Studio caches and restart. That should fix the problem:

The reason behind the first solution not working could be related on gradle cached dependencies problems, but who knows

Just you have to do >> open File --> Sync Project with Gradle Files and then after >> open File --> invalidate Android Studio caches / restart so done this problem.:)

sometimes Sync project with gradle File dosent work; you should check the compileSdkVersion in the "build.gradle" file , make them is the same number within all library/modlue

This issue is because the gradle file is not found when starting the project. To fix this ensure your connection to the internet is stable during project startup, the gradle file is downloaded automatically, after a successful download, You should be good!

This error mostly occurs when you're trying to open Android App from existing application and probably developed using different computer. Almost all the troubleshoot methods like File->Sync Project, Build->Clean, etc. Might not work.

This is applied only if you are trying to open the Adroid Application from existing application.

The proper way to evoid errors is only to open sub folder from the path not the root folder. Below is the example of how to properly open the Android application from existing application.

For example in your Message_App/messages/msg path, you must open msg folder not your Message_App folder.

Message_App/messages/msg

>msg
 >manifests
 >java
 >res

Issue happened to me when I changed the res>values>styles.xml

What I change was
"Theme.AppCompat.Light.DarkActionBar" --->>> "Base.Theme.AppCompat.Light.DarkActionBar"

Solutions I tried.

1. Build -> Rebuild Project (Not worked)
2. Close all files and Open again. Then Build -> Clean Project (Not worked) File -> Sync project with gradle files (Not worked)
3. Close the Android Studio while project still opened. Opened it again. - It Worked.

If nothing of the above steps work, Then simply undo the changes that you have recently made, and then build gradle. In my case, I have added one dependencies and this problem raised, so I removed that dependencies build the gradle and then again add it. Problem Solved..!!

I had this problem and it was because I didn't have the right API level installed (and I was also getting an error to that effect). I went into Tools --> SDK Manager and installed the API the system was telling me I needed (in my case, 30). I did that and restarted Android Studio and was able to get into XML files.