React native takes very long to load on device

Question

I've been developing a react-native app using the simulator for a while. On the simulator (iOS), the app loads very fast (on reload for eg). However, when I tried to load the app to the device, it spends between 1-3 minutes in the splash screen before loading into the app.

My project is fairly small, and has no extra resources other than the javascript. Looking at the documentation I couldn't find what might be the cause of the issue, though I suspect it has to do with the fact that it is not getting the JS from the packager local server.

What am I doing wrong?

(btw - react-native v0.31)

Answer 1

I ran into the same issue and discovered that it was because I was running my app on device in development mode. To get the performance you're looking for, you'll need to build and run the app in production or "release" mode. You can do this by passing in a --configuration option and setting it to Release using the React Native CLI:

$ react-native run-ios --configuration Release

If that doesn't do the trick, then you may need to build your app in "Release" mode from Xcode. To do that, navigate to your projects /ios directory and open the .xcodeproj file in Xcode. Choose your build target in the Toolbar. Scroll to the bottom and choose "Edit Scheme...". Then under Build Configuration, switch from "Debug" to "Release". Now build your app on your target device and it should be much more performant than before.

You can read more in the official React Native documentation under Running on Device: Building your app for production.

Answer 2

For me the issue was related to the wifi network of my development machine. I was using WPA2 Enterprise auth to connect to wifi on my development machine. I found that if I used a wired connection to connect to my network or if I used another wifi connection that used a different form of auth then the delay went away. I think the delay is a network timeout.