Another update: Using the set nav bar color changes the color of the "bar" so i think Chrome OS is trying to emulate a nav bar but when i do hide system ui i can't do maximize only fullscreen
Have you ever tried other Chromebooks? My school’s Chromebook has no black bar in project editor. Unfortunately, I can't download the companion app so I can't test it.
I would recommend you checking Chromebook’s Settings again because it also happens to your Google. Extension making the bar transparent also suggests that you might be able to turn it off in Settings.
ChatGPT
It looks like you’re seeing a known issue posted on the MIT App Inventor community forum where users report a black bar appearing when using the maximize mode on a Chromebook while running the Companion app. (MIT App Inventor Community)
Here’s a breakdown of what they're experiencing, what is known so far, and some possible work‑arounds:
It only happens in the Companion app environment (i.e., when using the MIT App Inventor Companion app) — they tested other apps (like something using Google Play) and didn’t see the bar. (MIT App Inventor Community)
One workaround reported: the user installed an extension called “Hidebars” to hide system UI. This seemed to remove the black bar, though it changed the way maximize vs fullscreen behaved. (MIT App Inventor Community)
Another observation: when they changed the nav‑bar color in their app (via “set nav bar color”), the bar’s color changed — which indicates that the black bar may be part of Chrome OS (or the Companion’s wrapper) drawing a navigation/system bar zone. (MIT App Inventor Community)
Possible causes
It may be a Chrome OS or Chromebook window‐management quirk: maximizing vs fullscreen differ, and the system may reserve a strip (system UI or nav bar) that doesn’t get hidden when the app is simply “maximized”.
The Companion app may be rendering in a mode (e.g., webview + Android container) where OS bars (navigation, status) are overlaid, and maximizing doesn’t hide them properly.
The nav‑bar color change behavior suggests the Companion app has some control over the bar area, but maybe there’s a mismatch between what the app requests and what Chrome OS enforces.
Because the issue doesn’t reproduce for all users, it might be device-specific (model of Chromebook), OS version, or interplay of extensions/settings.
Work‑arounds & tips
Try using fullscreen (F11 / Chrome OS equivalent) instead of maximize. One user suggested toggling full‑screen mode fixed the black bar (though possibly on a regular browser rather than the companion). (MIT App Inventor Community)
Use the “Hidebars” extension (or similar) to force hide system/navigation bars—this worked for the user albeit with some trade‑offs (couldn’t maximize, only fullscreen). (MIT App Inventor Community)
Check if your Chromebook has any newer OS or Chrome OS updates — the issue may be fixed in a later version.
Test on another Chromebook or user profile to isolate whether it’s device/setting specific (since another user “friend” said it wasn’t happening to him). (MIT App Inventor Community)
As a fallback, avoid maximizing and instead manually adjust window size to near‑full screen or use true fullscreen mode.
If you like, I can check for official bug‑reports for this issue (with MIT App Inventor & Chrome OS) and see if there’s a fix planned or known version where it’s resolved. Would you like me to do that?
I checked and no, I didn’t find an official documented bug‐fix or release note from MIT App Inventor that specifically addresses the “black bar when in maximize mode on Chromebook” issue. Here’s a summary of what I found, and what you might do next:
What I located
The issue is posted on the App Inventor community forum: “Black bar when in maximize mode, chromebook”. The thread describes the exact behaviour you mentioned: a black bar when the window is maximised on a Chromebook while using the Companion app. (MIT App Inventor Community)
The forum thread includes responses from other users trying to replicate the issue, and one moderator asking follow‑up questions (“Does this only happen when you have the Companion app open?”). (MIT App Inventor Community)
The official “App Inventor on Chromebooks” support page notes general setup instructions and limitations, but does not mention this specific maximize‐mode black bar issue. (MIT App Inventor)
The generic troubleshooting and FAQs for App Inventor likewise do not list this exact symptom as a known bug. (MIT App Inventor)
What we can infer
Because the issue is reported, it’s likely a bug (either in the Companion app, in Chrome OS’s Android‐app window handling, or in the way App Inventor uses Android apps on Chromebooks).
The fact that it only occurs in maximize mode (not fullscreen or normal window) suggests it might be tied to how the window frame or Android app container is handled on Chromebooks when “maximised” but not truly fullscreen.
Because it isn’t listed as an official bugfix, it may be unresolved, or possibly low priority or waiting for reproduction across more devices.
The App Inventor team does appear to monitor the community forum, so your report has visibility.
What you can do / suggest
In the forum thread you found, you could reply with details of your Chromebook model, Chrome OS version, Companion app version, and reproduce steps — this will help the MIT team or community members replicate and diagnose.
Check for Chrome OS updates and Companion app updates on the Play Store. If there’s a newer version of the Companion or Chrome OS that fixes window/hardware compatibility, updating might resolve the symptom.
As a workaround: Use fullscreen mode instead of maximise; or manually resize the window slightly smaller than full screen to avoid the black bar.
If you’re part of a managed Chromebook environment (school or institution), check whether windowing behavior or Android app container settings have been modified—sometimes IT policies or Chrome flags alter how Android apps are displayed.
Consider filing a bug report (if you haven’t already) via the forum or the “Bugs & Other Issues” category in the App Inventor forum, referencing the thread number and your environment details. The more reproducible data they have, the more likely a fix will be prioritized.
If you like, I can scan the open issues tracker (if available) for App Inventor and check Chrome OS issue trackers for related Android app windowing bugs on Chromebooks — to see whether this might actually be a Chrome OS bug rather than App Inventor’s. Would you like me to do that?