Debugging

For most parts of it React Native error aren’t descriptive at all, so you have to try and test a few techniques to get it to work. here are a few thing’s you can try

noVNC error 404

  • Sometimes we might see a 404 Error when we run the emulator, this usually happened when the vnc_auto.html file was changed to vnc_lite.html. to fix this, in your android-emulator:run change your Preview URL from http://${server.port.6080} to http://${server.port.6080}/vnc_lite.html

Console Log

  • We can use console.log for debugging, remember we created a command with the name adb-logcat:run try running it after starting the emulator. And you’ll see that all the logs from our Emulator are getting logged here. There are three types of logs
    • console.log
    • console.error
    • console.warn
  • console.error will show you a red screen on the emulator when called
  • console.warn will show you warning at the bottom of the screen
  • console.log won’t show up on the emulator but would be logged in the adb logcat

Sometimes when you are testing the app you might get a red screen with an error, and most of the times these errors are vague. So here are a few things you can do to make it work.

Stack trace

You can sometimes find where the error is just by looking at the error screen, in that case go back to your code and make the required changes. - Even if at the top you don’t see an error in a file that’s not familiar go down to see if you can find a file that you know of.

./gradlew clean

This command cleans your android project. run it after going into your android. here are the steps, - from the TravelLog directory run cd android - run ./gradlew clean - run react-native run-android from TravelLog directory

Re-install

As a last measure you can

  • uninstall the app from the emulator
  • stop packager server
  • restart the packager server
  • run your app with react-native run-android

Some common errors and fixes

here are some common error that you might encounter and how to fix them,

  • Can’t find variable: [yadayada]

    This is a common error and usually means that you forgot to import or initialize a function, method or a variable. just go to the line and verify

  • You have not accepted the license agreements of the following SDK components:

    This another creepy worm that we were prepared for but still slips out of our shoe, so here’s how to fix this issue.

    • copy this line : android update sdk --no-ui --all --filter "replace_with_required_sdk_component"
    • paste it in the codenvy workspace
    • change the replace_with_required_sdk_component to your component that requires license acceptance.
    • press enter and then enter y when it prompts to accepts the license.
      You are good to go!

  • You cannot render into anything but a top root”

Workspace stops while build and prompts for restart again and again

This issue is specific to codenvy and will start showing up as your project gets big, we encountered this error on [part9]

If nothing of the above work May God save you😜, Just kidding You can ask any of the mentors to help you debug anytime. Just make sure you first follow the above steps to save time.