Solution

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

c:\Users\lenger\Desktop\webrowser>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
Scanning folders for symlinks in c:\Users\lenger\Desktop\webrowser\node_modules (43ms)
Scanning folders for symlinks in c:\Users\lenger\Desktop\webrowser\node_modules (38ms)
Loading dependency graph, done.
bundle: start
bundle: finish
bundle: Writing bundle output to: android/app/src/main/assets/index.android.bundle
bundle: Done writing bundle output

Run react-native run-android again, you will find your modification work.