Taking screenshot while app is in background crashes the app

[zuboje]

Platform

Dart

Obfuscation

Disabled

Debug Info

Enabled

Doctor

[√] Flutter (Channel stable, 3.13.6, on Microsoft Windows [Version 10.0.22621.2283], locale en-US)
• Flutter version 3.13.6 on channel stable at C:\Users\Developer\source\repos\flutter
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• Framework revision ead455963c (12 days ago), 2023-09-26 18:28:17 -0700
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[√] Android toolchain - develop for Android devices (Android SDK version 33.0.1)
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[√] Visual Studio - develop Windows apps (Visual Studio Community 2022 17.7.4)
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[√] Connected device (4 available)
• moto g power 2022 (mobile) • ZY22GHDDBB • android-arm64 • Android 12 (API 31)
• Windows (desktop) • windows • windows-x64 • Microsoft Windows [Version 10.0.22621.2283]
• Chrome (web) • chrome • web-javascript • Google Chrome 117.0.5938.149
• Edge (web) • edge • web-javascript • Microsoft Edge 117.0.2045.43

[√] Network resources
• All expected network resources are available.

• No issues found!

Version

7.9.0

Steps to Reproduce

in main.dart setup following

runApp(
    SentryScreenshotWidget(
        child: MyApp(),
    ),
);

Run your application put your application in background or lock your phone, and create a function that will trigger an exception and have something like this:

try {
    DoSometuing();
    throw Exception('Hey something is wrong');
} catch (exception, stackTrace) {
    await Sentry.captureException(
        exception,
        stackTrace: stackTrace,
    );
}

This will throw exception Null check operator used on a null value

Expected Result

If the mobile app is not in the foreground and you cannot capture the screenshot it should ignore it or allow developers to control this based on the application state.

Actual Result

If you have set the mobile application with SentryScreenshotWidget, and the application is in the background when you try to capture an exception using sentry it will throw an exception:

_TypeError
Null check operator used on a null value
painting.dart in _Image.toByteData.. at line 1959

So essentially I have to try/catch for capturing exceptions.

Are you willing to submit a PR?

None

[stefanosiano]

hi @zuboje
thanks for your report! We are going to look into it

[denrase]

@zuboje This is a flutter rendering issue and it looks like the fix will part of the Flutter 3.15 Release.

Here's the issue: flutter/flutter#135245

We did implement a workaround where users can disable taking screenshots in the background, but we'll need to discuss if this is even worth including when there is a fix in the Flutter SDK on the way.