glance

An APM library for detecting UI jank in Flutter for mobile (Android/iOS).

NOTE: This package is experimental. APIs may change without notice before the stable version 1.0.

Building smooth APPs with Flutter is easy, but as your APP grows in complexity and faces a variety of user environments and devices, ensuring smooth performance in production can be challenging. Even if your app runs smoothly locally, it doesn't guarantee the same for all users. glance helps collect stack traces during UI jank, allowing you to pinpoint the exact function causing the performance issue, so you can resolve it effectively.

glance detects UI jank during the build phase as well as through various callbacks, such as, WidgetBindingObserver callbacks, touch events, and method channel callbacks. These cover most cases that cause UI jank. It works only in release or profile builds when your application is built with the --split-debug-info option.

Getting Started

Start UI Jank Detection

To receive UI jank information, implement your own reporter (JankDetectedReporter). Once you have the jank information, you can save the stack traces to a file, or upload them to your server, and symbolize them using the flutter symbolize command.

// Implement your `JankDetectedReporter`
class MyJankDetectedReporter extends JankDetectedReporter {
  @override
  void report(JankReport info) {
    final stackTrace = info.stackTrace.toString();
    // Save the stack traces to a file, or upload them to your server,
    // symbolize them using the `flutter symbolize` command.
  }
}

void main() {
  // Call `GlanceWidgetBinding.ensureInitialized()` first
  GlanceWidgetBinding.ensureInitialized();
  // Start UI Jank Detection
  Glance.instance.start(config: GlanceConfiguration(reporters: [MyJankDetectedReporter()]));

  runApp(const MyApp());
}

glance works only when you build your application with the --split-debug-info option (see Flutter documentation). For example, to build an Android APK:

flutter build apk --release --split-debug-info=debug-info

Symbolize the jank stack traces

After obtaining the glance stack traces, you can use the flutter symbolize command (see Flutter documentation) to symbolize them.

For example, assume you get the stack traces from info.stackTrace.toString() in the above code on Android and save them to my_stacktraces.txt file:

// my_stacktraces.txt

*** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
pid: 32542, tid: 32575, name 1.ui
os: android arch: arm64 comp: yes sim: no
build_id: '4dbecf547733e72ae1688d73ebb5f062'
isolate_dso_base: 7de0e44000, vm_dso_base: 7de0e44000
isolate_instructions: 7de0efa840, vm_instructions: 7de0ee4000
    #00 abs 0000007de0f63ae8 _kDartIsolateSnapshotInstructions+0x692a8
    #01 abs 0000007de0f63a04 _kDartIsolateSnapshotInstructions+0x691c4
    #02 abs 0000007de0fed7a8 _kDartIsolateSnapshotInstructions+0xf2f68
    #03 abs 0000007de10611b0 _kDartIsolateSnapshotInstructions+0x166970
    #04 abs 0000007de0facecc _kDartIsolateSnapshotInstructions+0xb268c
    #05 abs 0000007de106b3a0 _kDartIsolateSnapshotInstructions+0x170b60
    #06 abs 0000007de1023900 _kDartIsolateSnapshotInstructions+0x1290c0
    #07 abs 0000007de102320c _kDartIsolateSnapshotInstructions+0x1289cc
    #08 abs 0000007de10231d0 _kDartIsolateSnapshotInstructions+0x128990
    #09 abs 0000007de106c248 _kDartIsolateSnapshotInstructions+0x171a08
    #10 abs 0000007de106bfd4 _kDartIsolateSnapshotInstructions+0x171794

After running the flutter symbolize command:

flutter symbolize -i my_stacktraces.txt -d debug-info/app.android-arm64.symbols

You can get the symbolized stack traces like this:

*** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
pid: 32542, tid: 32575, name 1.ui
os: android arch: arm64 comp: yes sim: no
build_id: '4dbecf547733e72ae1688d73ebb5f062'
isolate_dso_base: 7de0e44000, vm_dso_base: 7de0e44000
isolate_instructions: 7de0efa840, vm_instructions: 7de0ee4000
#0      jsonEncode (third_party/dart/sdk/lib/convert/json.dart:114:10)
#1      expensiveFunction (/my/project/jank_app.dart:22:5)
#2      _BuildPhaseJankWidgetState.build (/my/project/build_phase_jank_test.dart:26:3)
#3      StatefulElement.build (/my/path/flutter/packages/flutter/lib/src/widgets/framework.dart:5592:3)
#4      Element.widget (/my/path/flutter/packages/flutter/lib/src/widgets/framework.dart)
#5      ComponentElement.performRebuild (/my/path/flutter/packages/flutter/lib/src/widgets/framework.dart:5486:31)
#6      StatefulElement.performRebuild (/my/path/flutter/packages/flutter/lib/src/widgets/framework.dart:5638:3)
#7      List.iterator (third_party/dart/sdk/lib/_internal/vm/lib/growable_array.dart:507:16)
#8      BuildOwner.buildScope (/my/path/flutter/packages/flutter/lib/src/widgets/framework.dart:2952:37)
#9      WidgetsBinding.drawFrame (/my/path/flutter/packages/flutter/lib/src/widgets/binding.dart:1230:13)
#10     RendererBinding._handlePersistentFrameCallback (/my/path/flutter/packages/flutter/lib/src/rendering/binding.dart:469:5)

Symbolize Automatically

Some tools, like Firebase and Sentry, can automatically symbolize the stack traces if you upload the symbols. This is helpful if you do not have a self-hosted server. See more detail:

• Firebase: https://firebase.google.com/docs/crashlytics/get-deobfuscated-reports?platform=flutter
• Sentry: https://docs.sentry.io/platforms/flutter/upload-debug/

Acknowledgements

Thanks to thread_collect_stack_example for the inspiration, which made this project possible.

License

Some files in this project are licensed under the BSD 3-Clause "New" or "Revised" License from thread_collect_stack_example. See the LICENSE-original file for details.

The rest of the project is licensed under the MIT License. See the LICENSE file for details.