I tried to set the path in environmental variables but it doesn\'t work.
Error like as below: \'adb\' is not recognized as an internal or external command, operable
First of all you have to set environment variable of your android sdk's platform-tool
Start > Control Panel > System > Advanced System Settings > Environment Variables...
In this Environment Variables window, in the User variables section for (your-username) highlight Path and click Edit...
add this path: C:\Users\your-username\AppData\Local\Android\sdk\platform-tools;
its a default sdk path in windows OS. if you have different location than add your sdk path, than click OK until environment variable popup close.
If you already have a Command Prompt window open, close it then re-open and the adb devices command should then work.
Step 2 :
if its still not work than add local.properties file to your project
paste your Android SDK path like below
in Windows sdk.dir = C:/Users/USERNAME/AppData/Local/Android/sdk
in macOS sdk.dir = /Users/USERNAME/Library/Android/sdk
in linux sdk.dir = /home/USERNAME/Android/Sdk
Replace USERNAME with your user name
Now, Run react-native run-android
in your terminal