ERROR: Module 'app': platform 'android-28' not found. and Design editor is unavailable until after a successful project sync
Solution 1:
Go to Tools->sdk manager->install API Level 28 then restart.
Solution 2:
- go to Tools
- Select SDK Manager
- Under SDK Platforms select Android 9.0 (Pie) (API 28)
- Then Apply and Download the API
Solution 3:
I face the same problem. First, install API Level 28 & Restart the Android studio.
Solution 4:
First of all! you need to update your sdk manager that too essential tools are: build tools platform tools tools and android Emulator
.....
Now go to LOGCAT , click on configure sdk..... put it to latest and click autoconfig button for each bar.
thats it rebuild it! You are done with 100 percent% successful error solving, Your Activity.xml file will be displayed with out any warning or error!
Solution 5:
After reinstalling and upgrading my android studio to android 4, I faced the same challnge. but what I did was to go to tool->sdk manager and then install some other APIs including the error messages API 28 not installed and it works fine.