一 .适应了更多的平台，尤其是Web

Platform Adaptive Apps: Flutter Folio Sample

Now that Flutter supports three platforms for production apps (Android, iOS, and the web) and three more in beta (Windows, macOS, and Linux）

二 .增加了空安全的机制

Sound Null Safety

Sound null safety is a significant addition to the Dart language, which further strengthens the type system by distinguishing nullable types from non-nullable types. This enables developers to prevent null error crashes, a common reason for apps to crash. By incorporating null checks into the type system, these errors can be caught during development, thus preventing crashes in production. Sound null safety is fully supported in stable as of Flutter 2, which contains Dart 2.12. For more details, see the Dart 2.12 blog post.

三 .重大改变升级帮助

一些过时的Api改成新的Api,可以试试这个。但是第三方SDK我想是个麻烦的事情

$ dart fix --dry-run

四.代码错误检查与修复建议

One new feature that helps you zero in on your issues even before you’ve launched DevTools is the ability for Android Studio, IntelliJ, or Visual Studio Code to notice when there’s a common exception and offer to bring it up in DevTools to help you debug it. For example, the following shows an overflow exception has been thrown in your app, which brings up an option in Visual Studio Code to debug the issue in DevTools.

五.App性能调试

Another new feature in DevTools is the ability to easily see an image that’s at a higher resolution than it’s displayed, which helps track down excessive app size and memory usage. To enable this feature, enable the Invert Oversized Images in the Flutter Inspector

重大更新如下

Breaking Changes

We’ve made the following breaking changes for Flutter 2, many of which can be automatically mitigated using the dart fix command or the quick fixes in your IDE of choice:

61366 Continue the clipBehavior breaking change

66700 Default FittedBox’s clipBehavior to none

68905 Remove nullOk parameter from Cupertino color resolution APIs

69808 Remove nullOk from Scaffold.of and ScaffoldMessenger.of, create maybeOf for both

68910 Remove nullOk parameter from Router.of and make it return a non-nullable value

68911 Add maybeLocaleOf to Localizations

68736 Remove nullOK in Media.queryOf

68917 Remove nullOk parameter from Focus.of, FocusTraversalOrder.of, and FocusTraversalGroup.of

68921 Remove nullOk parameter from Shortcuts.of, Actions.find, and Actions.handler

68925 Remove nullOk parameter from AnimatedList.of and SliverAnimatedList.of

69620 Remove deprecated methods from BuildContex

70726 Remove the nullOk parameter from Navigator.of and add Navigator.maybeOft

72017 Remove deprecated CupertinoTextThemeData.brightness

72395 Remove deprecated [PointerEnterEvent, PointerExitEvent].fromHoverEvent

72532 Remove deprecated showDialog.child

72890 Remove deprecated Scaffold.resizeToAvoidBottomPadding

72893 Remove deprecated WidgetsBinding.[deferFirstFrameReport, allowFirstFrameReport]

72901 Remove deprecated StatefulElement.inheritFromElement

72903 Remove deprecated Element methods

73604 Remove deprecated CupertinoDialog

73745 Remove deprecated actionsForegroundColor from Cupertino[Sliver]NavigationBar

73746 Remove deprecated ButtonTheme.bar

73747 Remove span deprecations

73748 Remove deprecated RenderView.scheduleInitialFrame

73749 Remove deprecated Layer.findAll

75657 Remove vestigial nullOk parameter from Localizations.localeOf

74680 Remove nullOk from Actions.invoke, add Actions.maybeInvoke