App closes without error mesasge

[Taifun]

you should switch screens correctly, see also

App Inventor Tutorials and Examples: Manager Screen | Pura Vida Apps

if it still does not work after fixing that, then one method to find out why you get a runtime error is to use logcat

Capturing Device Logs using adb logcat

ADB is a command-line utility that that can be used to control your device over USB from a computer. It will allow you to install / uninstall and or view logs on your device. This could be very handy when there are issues with a specific app and you like to view the logs for information that may lead to identify the cause of error. In this post, we’ll discuss how to install and use ADB. Installation: ADB comes with Android SDK. However, you can download ONLY the ADB files from HERE . Download…

EDIT: see also tip 1 here

General Tips and Tricks for App Inventor

This list was made by @Taifun Use different screens wisely Before starting to create another screen, first you should think about is it really necessary? See also Building apps with many screens and SteveJG's post about advantages/disadvantages, because in only one screen you also can use vertical arrangements to simulate different screens, just set the arrangements to visible = true/false as needed... If you decided to use different screens, then you should switch them correctly, else you …

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