You haven't started the bundler yet. Run npm start or react-native start in the root directory of your project before react-native run-android.
These steps really help me:
Step 1: Create a directory in android/app/src/main/assets
Linux command: mkdir android/app/src/main/assets
Step 2: Rename index.android.js (in root directory) to index.js (Maybe there is an index.js file in which case you do not need to rename it) then run the following command:
react-native bundle --platform android --dev false --entry-file index.js --bundle-output android/app/src/main/assets/index.android.bundle --assets-dest android/app/src/main/res
Step 3:
Build your APK: react-native run-android
Please use index.js in latest version.
Enjoy :)
If you have everything correctly configured then try this:
adb reverse tcp:8081 tcp:8081
Why?
When the RN packager is running, there is an active web server accessible in your browser at 127.0.0.1:8081. It's from this server that the JS bundle for your application is served and refreshed as you make changes. Without the reverse proxy, your phone wouldn't be able to connect to that address.
All credits to Swingline0 .