# 性能常见问题和回答 > 关于 Flutter 性能的常见问题 This page collects some frequently asked questions about evaluating and debugging Flutter's performance. 本篇收集了一些关于评估和调试 Flutter 性能的常见问题。 * Which performance dashboards have metrics that are related to Flutter? 哪些性能仪表盘有 Flutter 相关的指标？ * [Flutter dashboard on appspot][] [在 Appspot 上的 Flutter 仪表盘][Flutter dashboard on appspot] * [Flutter Skia dashboard][] [Flutter Skia 仪表盘][Flutter Skia dashboard] * [Flutter Engine Skia dashboard][] [Flutter Engine Skia 仪表盘][Flutter Engine Skia dashboard] [Flutter dashboard on appspot]: https://flutter-dashboard.appspot.com/ [Flutter engine Skia dashboard]: https://flutter-engine-perf.skia.org/t/?subset=regressions [Flutter Skia dashboard]: https://flutter-flutter-perf.skia.org/t/?subset=regressions * How do I add a benchmark to Flutter? 我如何向 Flutter 添加一个基准测试？ * [How to write a render speed test for Flutter][speed-test] [如何编写 Flutter 的渲染速度测试][speed-test] * [How to write a memory test for Flutter][memory-test] [如何编写 Flutter 的内存测试][memory-test] [memory-test]: https://github.com/flutter/flutter/blob/main/docs/contributing/testing/How-to-write-a-memory-test-for-Flutter.md [speed-test]: https://github.com/flutter/flutter/blob/main/docs/contributing/testing/How-to-write-a-render-speed-test-for-Flutter.md * What are some tools for capturing and analyzing performance metrics? 有哪些捕捉和分析性能指标的工具？ * [Dart/Flutter DevTools](/tools/devtools) * [Apple instruments](https://en.wikipedia.org/wiki/Instruments_(software)) * [Linux perf](https://en.wikipedia.org/wiki/Perf_(Linux)) * [Chrome tracing (enter `about:tracing` in your Chrome URL field)][tracing] [Chrome tracing（在浏览器地址栏输入 `about:tracing`）][tracing] * [Android systrace (`adb systrace`)][systrace] * [Fuchsia `fx traceutil`][traceutil] * [Perfetto](https://ui.perfetto.dev/) * [speedscope](https://www.speedscope.app/) [systrace]: https://developer.android.google.cn/studio/profile/systrace [tracing]: https://www.chromium.org/developers/how-tos/trace-event-profiling-tool [traceutil]: https://fuchsia.dev/fuchsia-src/development/tracing/usage-guide * My Flutter app looks janky or stutters. How do I fix it? 我的 Flutter 应用程序很卡顿，性能很糟糕。 怎么样才能修复这些问题？ * [Improving rendering performance][] [提高渲染性能][Improving rendering performance] [Improving rendering performance]: /perf/rendering-performance * What are some costly performance operations that I need to be careful with? 有哪些特别消耗性能的操作是我需要注意的？ * [`Opacity`][], [`Clip.antiAliasWithSaveLayer`][], or anything that triggers [`saveLayer`][] [`Opacity`][]、[`Clip.antiAliasWithSaveLayer`][] 或任何能触发 [`saveLayer`][] 的操作。 * [`ImageFilter`][] * Also see [Performance best practices][] 查阅 [性能优化最佳实践][Performance best practices] [`Clip.antiAliasWithSaveLayer`]: https://api.flutter-io.cn/flutter/dart-ui/Clip.html#antiAliasWithSaveLayer [`ImageFilter`]: https://api.flutter-io.cn/flutter/dart-ui/ImageFilter-class.html [`Opacity`]: https://api.flutter-io.cn/flutter/widgets/Opacity-class.html [Performance best practices]: /perf/best-practices [`savelayer`]: https://api.flutter-io.cn/flutter/dart-ui/Canvas/saveLayer.html * How do I tell which widgets in my Flutter app are rebuilt in each frame? 我如何才能知道 Flutter 应用程序中哪些 widget 在哪一帧中被重新构建？ * Set [`debugProfileBuildsEnabled`][] true in [widgets/debug.dart][debug.dart]. 将 [widgets/debug.dart][debug.dart] 中的 [`debugProfileBuildsEnabled`][] 设置为 true。 * Alternatively, change the `performRebuild` function in [widgets/framework.dart][framework.dart] to ignore `debugProfileBuildsEnabled` and always call `Timeline.startSync(...)/finish`. 或者，改变 [widgets/framework.dart][framework.dart] 中的 `performRebuild` 函数，忽略 `debugProfileBuildsEnabled`， 并始终调用 `Timeline.startSync(...)/finish`。 * If you use IntelliJ, a GUI view of this data is available. Select **Track widget rebuilds**, and your IDE displays which the widgets rebuild. 如果你使用 IntelliJ，就可以看见这些数据的视图。 在 IntelliJ 的 Flutter Performance 工具中 勾选 **Track widget rebuilds**， 你就能在 IDE 中直观地看见哪些 widget 进行了重建。 [`debugProfileBuildsEnabled`]: https://api.flutter-io.cn/flutter/widgets/debugProfileBuildsEnabled.html [debug.dart]: https://github.com/flutter/flutter/blob/main/packages/flutter/lib/src/widgets/debug.dart [framework.dart]: https://github.com/flutter/flutter/blob/main/packages/flutter/lib/src/widgets/framework.dart * How do I query the target frames per second (of the display)? 我如何查询显示器的刷新率？ * [Get the display refresh rate][] [获取显示器刷新率][Get the display refresh rate] [Get the display refresh rate]: https://github.com/flutter/flutter/blob/main/docs/engine/Engine-specific-Service-Protocol-extensions.md#get-the-display-refresh-rate-_fluttergetdisplayrefreshrate * How to solve my app's poor animations caused by an expensive Dart async function call that is blocking the UI thread? 如何解决我的应用程序因高消耗的 Dart 异步函数调用 阻塞了 UI 线程，而导致动画效果不佳？ * Spawn another isolate using the [`compute()`][] method, as demonstrated in [Parse JSON in the background][] cookbook. 使用 [`compute()`][] 方法生成另一个 isolate， 例如 [在后台处理 JSON 数据解析][Parse JSON in the background] 实用教程 (Cookbook) 中所演示的。 [`compute()`]: https://api.flutter-io.cn/flutter/foundation/compute-constant.html [Parse JSON in the background]: /cookbook/networking/background-parsing * How do I determine my Flutter app's package size that a user will download? 我如何确定用户下载的 Flutter 应用程序包的体积？ * See [Measuring your app's size][] 请查阅 [测量你的应用体积][Measuring your app's size] [Measuring your app's size]: /perf/app-size * How do I see the breakdown of the Flutter engine size? 我如何才能看到 Flutter engine 内架构细分的体积？ * Visit the [binary size dashboard][], and replace the git hash in the URL with a recent commit hash from [Flutter's GitHub commits][]. 访问 [binary size dashboard][]， 用 [GitHub 上 Flutter 仓库][Flutter's GitHub commits] 最近提交的 hash 值替换 URL 中的 hash 值。 [binary size dashboard]: https://storage.flutter-io.cn/flutter_infra_release/flutter/241c87ad800beeab545ab867354d4683d5bfb6ce/android-arm-release/sizes/index.html [Flutter's GitHub commits]: https://github.com/flutter/flutter/commits/main * How can I take a screenshot of an app that is running and export it as a SKP file? 我如何才能对正在运行的应用程序进行截图， 并将其导出 SKP 文件？ * Run `flutter screenshot --type=skia --observatory-uri=...` 运行 `flutter screenshot --type=skia --observatory-uri=...` 命令 * Note a known issue viewing screenshots: 注意，一个查看截图的已知问题： * [Issue 21237][]: Doesn't record images in real devices. [Issue 21237][]: 无法在真机中截图。 * To analyze and visualize the SKP file, check out the [Skia WASM debugger][]. 分析和可视化 SKP 文件，请使用 [Skia WASM debugger][]。 [Issue 21237]: https://github.com/flutter/flutter/issues/21237 [Skia WASM debugger]: https://debugger.skia.org/ * How do I retrieve the shader persistent cache from a device? 如何从设备上读取着色器持久化缓存？ * On Android, you can do the following: 在 Android 上，你可以进行以下操作： ```console adb shell run-as cp -r adb pull ``` * How do I perform a trace in Fuchsia? 我如何在 Fuchsia 中进行追踪？ * See [Fuchsia tracing guidelines][traceutil] 请查阅 [Fuchsia 追踪指南][traceutil]