React Native应用程序无法在USB或APK格式的Android上构建，但在模拟器中可以正常构建

Question

My react-native app builds and runs perfectly fine in emulator, but whenever I try to build to a USB Device I get the following error:

Unable to load script from assets 'index.android.bundle'. Make sure your bundle is packaged correctly or you're running a package server.

jniLoadScriptFromAssets
catalystInstanceImpl.java

loadScriptFromAssets
JSBundleLoader.java:31

runJSBundle
CatalystInstanceImpl.java:234

CreateREactContext
ReactInstanceManager.java:114*

---

In the AndroidStudio debug console I'm seeing the following errors on build:

D/ReactNative: Initializing React Xplat Bridge after initializeBridge
               CatalystInstanceImpl.runJSBundle()
E/unknown:ReactNative: Exception in native call
                       java.lang.RuntimeException: Unable to load script from assets 'index.android.bundle'. Make sure your bundle is packaged correctly or you're running a packager server.
                           at com.facebook.react.bridge.CatalystInstanceImpl.jniLoadScriptFromAssets(Native Method)
                           at com.facebook.react.bridge.CatalystInstanceImpl.loadScriptFromAssets(CatalystInstanceImpl.java:216)
                           at com.facebook.react.bridge.JSBundleLoader$1.loadScript(JSBundleLoader.java:31)
                           at com.facebook.react.bridge.CatalystInstanceImpl.runJSBundle(CatalystInstanceImpl.java:234)
                           at com.facebook.react.ReactInstanceManager.createReactContext(ReactInstanceManager.java:1114)
                           at com.facebook.react.ReactInstanceManager.access$900(ReactInstanceManager.java:113)
                           at com.facebook.react.ReactInstanceManager$5.run(ReactInstanceManager.java:911)
                           at java.lang.Thread.run(Thread.java:764)

I'm stuck and tired of banging my head against the wall.

Answer 1

Debug Builds

If you're starting your build from within Android Studio, I found that it doesn't always bundle the Javascript code with the built app. To fix it, run your app on the USB device with:

react-native run-android

I've had much better results using the react-native CLI tool than with Android Studio.

Release Builds

Currently (as of React Native v0.56), there is a bug with bundling image assets that might be affecting you. In my experience, Android Studio would build the signed APK just fine, but would fail to include the bundled Javascript when using the latest Gradle. There is a fix coming in 0.57, but until then, there are several workarounds described in the related issue and pull request .

Answer 2

I have seen this error before, then I found that I didn't start up react native package server correctly.

You should first startup the react native server(using react-native start ), then you can begin installing your app by using android-studio.