Flutter 3.0.0 發行說明

本頁為 3.0.0 版本的發行說明。 如需後續錯誤修正版本的相關資訊， 請參閱我們的 CHANGELOG。

當你遷移至 Flutter 3 時， 你可能會看到如下的警告訊息：

Warning: Operand of null-aware operation '!' has type 'SchedulerBinding' which excludes null.

這些問題是由於 API 的簡化（bindings 上的 instance 屬性現在為 non-nullable），再加上編譯器會積極回報任何多餘的 null-aware 運算子（例如 ! 和 ?.）在不需要時被使用所導致。

如果發生這種情況，可能有幾個不同的原因與對應的解決方法：

如果你的相依套件（dependencies）有使用 bindings，它們可能需要更新以消除這些警告。除了冗長的警告訊息外，你的建置（builds）應該不會受到影響。你目前可以先忽略這些警告（也可以聯絡相依套件的開發者，建議他們進行更新）。

如果問題是出現在你自己的程式碼中，你可以執行 dart fix --apply 來進行更新。這應該可以解決所有警告。

如果你的程式碼需要同時支援 Flutter 3 和更早的版本（例如你的程式碼是一個函式庫），那麼你可以將對 binding.instance 的呼叫包裝在如下的方法中：

/// This allows a value of type T or T?
/// to be treated as a value of type T?.
///
/// We use this so that APIs that have become
/// non-nullable can still be used with `!` and `?`
/// to support older versions of the API as well.
T? _ambiguate<T>(T? value) => value;

例如，請勿使用以下寫法：

SchedulerBinding.instance!.addPostFrameCallback(...);

你可以使用：

_ambiguate(SchedulerBinding.instance)!.addPostFrameCallback(...);

當你不再需要支援 Flutter 3.0.0 之前的版本時，你可以將這段移除，並以以下內容取代：

SchedulerBinding.instance.addPostFrameCallback(...);

如果錯誤訊息沒有指向你的某個相依套件， 且dart fix --apply無法解決問題， 或者警告為致命錯誤 （例如，應用程式拒絕執行），請 回報錯誤。

本次版本包含以下變更：

• 還原「[Fonts] 更新 icons」@guidezpl 於 https://github.com/flutter/flutter/pull/95537
• 改善 iOS 上 barrierColor 及全螢幕 Cupertino 頁面轉場的邊緣裝飾擬真度 @willlockwood 於 https://github.com/flutter/flutter/pull/96115
• [Fonts] 更新 icons @guidezpl 於 https://github.com/flutter/flutter/pull/96007
• 允許 Checkboxes 在 DataTables 中從 CheckboxTheme 繼承顏色 @willlockwood 於 https://github.com/flutter/flutter/pull/95210
• 修正自動填充資格檢查 @LongCatIsLooong 於 https://github.com/flutter/flutter/pull/95944
• [DropdownButtonFormField] 新增 borderRadius 屬性 @dheerajv09 於 https://github.com/flutter/flutter/pull/94455
• 修正 DataTable _SortArrow 在狀態更新時改變方向的問題 @markusaksli-nc 於 https://github.com/flutter/flutter/pull/96195
• 修正拼字錯誤 @goderbauer 於 https://github.com/flutter/flutter/pull/96154
• RawKeyboard 重複事件，以及 SingleActivator.includeRepeats @dkwingsmt 於 https://github.com/flutter/flutter/pull/95224
• InteractiveViewer scaleFactor @justinmc 於 https://github.com/flutter/flutter/pull/96295
• 再次提交「確保 engineLayer 在 OpacityLayer 被禁用時正確釋放」@dnfield 於 https://github.com/flutter/flutter/pull/96233
• 當 obscureText 設定於 TextField 時，禁止複製與剪下 @gspencergoog 於 https://github.com/flutter/flutter/pull/96308
• 還原「當 obscureText 設定於 TextField 時，禁止複製與剪下 (#96233)」@gspencergoog 於 https://github.com/flutter/flutter/pull/95993
• 修正 paints..something 與 paints..everything 在應該失敗時卻成功的問題 @willlockwood 於 https://github.com/flutter/flutter/pull/94623
• 修正當 TabBar.tabs 長度變更時的 RangeError 錯誤 @werainkhatri 於 https://github.com/flutter/flutter/pull/95061
• 讓 FocusNode.traversalChildren 不受父層 canRequestFocus 影響 @gspencergoog 於 https://github.com/flutter/flutter/pull/95894
• 修正 scrollbar 錯誤 @xu-baolin 於 https://github.com/flutter/flutter/pull/96144
• 保留渲染後，LeaderLayer.applyTransform 不再導致崩潰 @goderbauer 於 https://github.com/flutter/flutter/pull/95977
• LayerLink 可暫時允許多個 leader @chunhtai 於 https://github.com/flutter/flutter/pull/96245
• TextEditingValue 預設選取範圍文件 @justinmc 於 https://github.com/flutter/flutter/pull/94626
• 新增標記子樹為不可遍歷的能力 @werainkhatri 於 https://github.com/flutter/flutter/pull/96224
• InkResponse 當 onTapDown 不為 null 時啟用 @markusaksli-nc 於 https://github.com/flutter/flutter/pull/96435
• InkWell.overlayColor 現在會根據 MaterialState.pressed 解析 @HansMuller 於 https://github.com/flutter/flutter/pull/75472
• 支援 Scribble 手寫輸入 @fbcouch 於 https://github.com/flutter/flutter/pull/96102
• [RenderListWheelViewport] 更新內容尺寸以防止 scroll offset 變動 @xu-baolin 於 https://github.com/flutter/flutter/pull/96388
• 修正 Dialog 對齊文件 @TahaTesser 於 https://github.com/flutter/flutter/pull/96420
• 啟用 no_leading_underscores_for_library_prefixes @goderbauer 於 https://github.com/flutter/flutter/pull/96483
• 在 RawKeyEventDataWeb 中公開 keyCode 欄位 @b-luk 於 https://github.com/flutter/flutter/pull/96486
• 為 LeaderLayer 啟用更多保留渲染機會 @goderbauer 於 https://github.com/flutter/flutter/pull/94486
• 將 FloatingActionButton 遷移至 Material 3 @darrenaustin 於 https://github.com/flutter/flutter/pull/96089
• 讓 DraggableScrollableController 成為 ChangeNotifier @caseycrogers 於 https://github.com/flutter/flutter/pull/96417
• 啟用 unnecessary_late @goderbauer 於 https://github.com/flutter/flutter/pull/96482
• 修正 NestedScrollView 的 scroll 通知 @Piinks 於 https://github.com/flutter/flutter/pull/96532
• MaterialStateProperty 文件 @Piinks 於 https://github.com/flutter/flutter/pull/96555
• 新增 onPointerHover 的 debug 屬性 @WasserEsser 於 https://github.com/flutter/flutter/pull/96546
• Date Picker 年份選擇器應以「按鈕」對無障礙框架宣告 @darrenaustin 於 https://github.com/flutter/flutter/pull/96615
• 還原「支援 Scribble 手寫輸入」@LongCatIsLooong 於 https://github.com/flutter/flutter/pull/96560
• 在 TapGestureRecognizer 新增支援裝置列表 @chunhtai 於 https://github.com/flutter/flutter/pull/96553
• 修正 UNUSED_ELEMENT_PARAMETER 於欄位初始化器 @scheglov 於 https://github.com/flutter/flutter/pull/95948
• Mac cmd + shift + 左/右鍵 @justinmc 於 https://github.com/flutter/flutter/pull/96563
• 將 ReorderableListView 自動捲動邏輯模組化 @chunhtai 於 https://github.com/flutter/flutter/pull/96623
• Slider: 新增可主題化滑鼠游標 v2 @HansMuller 於 https://github.com/flutter/flutter/pull/96561
• 設定 disabled 按鈕的「基本」滑鼠游標，PR #89346 @HansMuller 於 https://github.com/flutter/flutter/pull/96377
• 修正 [_ViewportElement] RenderObjectChild 更新錯誤 @xu-baolin 於 https://github.com/flutter/flutter/pull/95685
• 提供 Appbar 的 foregroundColor 給套件授權頁面標題 @TahaTesser 於 https://github.com/flutter/flutter/pull/96632
• 新增 CustomMultiChildLayout 範例 @gspencergoog 於 https://github.com/flutter/flutter/pull/96567
• PopupMenu: 新增可主題化滑鼠游標 v2 @HansMuller 於 https://github.com/flutter/flutter/pull/96252
• 新增 TabBar.splashFactory、TabBarTheme.splashFactory、overlayColor @HansMuller 於 https://github.com/flutter/flutter/pull/96551
• [framework] _debugVerifyIllFatedPopulation 不再進行 null 斷言 @jonahwilliams 於 https://github.com/flutter/flutter/pull/96309
• 當文字欄位為隱藏狀態時，禁止複製與剪下 @gspencergoog 於 https://github.com/flutter/flutter/pull/96484
• feat: 小工具文件新增更多 YouTube 參考 @albertodev01 於 https://github.com/flutter/flutter/pull/96599
• 更新 adaptive slider 文件 @maheshmnj 於 https://github.com/flutter/flutter/pull/96684
• 修正 UNUSED_ELEMENT_PARAMETER 於未使用欄位初始化參數 @scheglov 於 https://github.com/flutter/flutter/pull/96657
• feat: PopupMenuButton 新增自訂 padding @arafaysaleem 於 https://github.com/flutter/flutter/pull/96644
• [framework] 移除 Element 的 hashcode 覆寫 @jonahwilliams 於 https://github.com/flutter/flutter/pull/95596
• 初始化 element tree 時不再過早分配繼承元件快取 @jonahwilliams 於 https://github.com/flutter/flutter/pull/96781
• 還原「feat: PopupMenuButton 新增自訂 padding (#96657)」@gspencergoog 於 https://github.com/flutter/flutter/pull/96627
• 修正 animate to curve 參數 @caseycrogers 於 https://github.com/flutter/flutter/pull/96636
• 清理滑鼠區域程式碼 @chunhtai 於 https://github.com/flutter/flutter/pull/96695
• 防止 DropdownButton 將 borderRadius 屬性套用於清單首尾元素 @chinmoy12c 於 https://github.com/flutter/flutter/pull/92436
• TabPageSelector 新增 BorderStyle 屬性 @chinmoy12c 於 https://github.com/flutter/flutter/pull/96844
• 移除重複的 hashCode 值並補上缺少的逗號 @TahaTesser 於 https://github.com/flutter/flutter/pull/96876
• Date Picker 的下/上一個月按鈕語意移除日期 @darrenaustin 於 https://github.com/flutter/flutter/pull/96880
• chore: 文件註解新增 YouTube 參考 @albertodev01 於 https://github.com/flutter/flutter/pull/96194
• chore(flutter_test): 更新 'matchesGoldenFile' 文件 @albertodev01 於 https://github.com/flutter/flutter/pull/96296
• 使用 strict-raw-types 分析取代 no-implicit-dynamic @srawlins 於 https://github.com/flutter/flutter/pull/96874
• [Keyboard] 派發單一合成的 KeyEvent @dkwingsmt 於 https://github.com/flutter/flutter/pull/96884
• [web] 驗證 WebDriver 回應 @yjbanov 於 https://github.com/flutter/flutter/pull/95525
• 當圖片串流監聽器異步加入時，異步呼叫監聽器 @WasserEsser 於 https://github.com/flutter/flutter/pull/96944
• chore: didUpdateWidget 呼叫順序提前 @albertodev01 於 https://github.com/flutter/flutter/pull/96530
• 說明 MaterialApp 在無 Material Widget 時如何渲染文字樣式 @TahaTesser 於 https://github.com/flutter/flutter/pull/96422
• 啟用 no_leading_underscores_for_local_identifiers @goderbauer 於 https://github.com/flutter/flutter/pull/96593
• 新增控制 AnimatedCrossFade 是否可排除底層子元件焦點的能力 @TahaTesser 於 https://github.com/flutter/flutter/pull/96960
• ScaffoldState 新增 closeDrawer 與 closeEndDrawer @pedromassango 於 https://github.com/flutter/flutter/pull/95423
• PageView 捲動物理行為與 Android 一致 @nt4f04uNd 於 https://github.com/flutter/flutter/pull/96740
• ListTile: 新增可主題化滑鼠游標 @TahaTesser 於 https://github.com/flutter/flutter/pull/95714
• 新增 CheckboxListTile.checkboxShape @werainkhatri 於 https://github.com/flutter/flutter/pull/96810
• 允許 layerlink 的現有 leader 在前一個 leader 分離前可先分離 @chunhtai 於 https://github.com/flutter/flutter/pull/83638
• 將陰影導出至 Icon API @mateusfccp 於 https://github.com/flutter/flutter/pull/96957
• Scrollbar isAlwaysShown 棄用，改為 thumbVisibility @Piinks 於 https://github.com/flutter/flutter/pull/96541
• 文字輸入連線重啟後顯示鍵盤 @LongCatIsLooong 於 https://github.com/flutter/flutter/pull/97150
• 還原「PageView 捲動物理行為與 Android 一致」@Piinks 於 https://github.com/flutter/flutter/pull/97155
• [framework] 移除多餘的型別轉換 @jonahwilliams 於 https://github.com/flutter/flutter/pull/92959
• CupertinoPickerDefaultSelectionOverlay 新增 direction @Dan-Crane 於 https://github.com/flutter/flutter/pull/97154
• 放寬 routerReportsNewRouteInformation 函式簽名限制 @chunhtai 於 https://github.com/flutter/flutter/pull/91415
• 新增 CommonFinders.bySubtype<T extends Widget>() finder @lrhn 於 https://github.com/flutter/flutter/pull/96574
• ScrollsToTop 使用更合適的曲線 @SuhwanCha 於 https://github.com/flutter/flutter/pull/97173
• Scrollbar hoverThickness 與 showTrackOnHover 棄用 @Piinks 於 https://github.com/flutter/flutter/pull/91148
• PopupMenuButton 新增 splashRadius @Moluram 於 https://github.com/flutter/flutter/pull/97175
• [framework] 讓 HitTestEntry 支援泛型 @jonahwilliams 於 https://github.com/flutter/flutter/pull/93312
• _AnimatedIconPainter 先鏡像再縮放 @Amir-P 於 https://github.com/flutter/flutter/pull/85954
• Flutter web 新增 NetworkImage headers 支援 @jonas-martinez 於 https://github.com/flutter/flutter/pull/96881
• 再次提交「支援 Scribble 手寫輸入 (#96615)」@fbcouch 於 https://github.com/flutter/flutter/pull/97405
• 還原 Scribble reland @justinmc 於 https://github.com/flutter/flutter/pull/97335
• 更新 RawScrollbar 支援 track @Piinks 於 https://github.com/flutter/flutter/pull/96174
• Chips 棄用 useDeleteButtonTooltip @RoyARG02 於 https://github.com/flutter/flutter/pull/97254
• RefreshIndicator：新增互動範例 @TahaTesser 於 https://github.com/flutter/flutter/pull/93621
• 新增 CupertinoTimerPicker 互動範例 @TahaTesser 於 https://github.com/flutter/flutter/pull/95906
• 修正 DropdownButtonFormField 點擊區域並將 InkWell 加入 DropdownButton @TahaTesser 於 https://github.com/flutter/flutter/pull/97394
• 修正 navigator 可處理重複 page key 的 route @chunhtai 於 https://github.com/flutter/flutter/pull/96681
• 更新 PopupMenuButton 範例 @TahaTesser 於 https://github.com/flutter/flutter/pull/96904
• [Icons] 防止替換後出現雙底線 @guidezpl 於 https://github.com/flutter/flutter/pull/97493
• 改善 dart fix 測試文件 @werainkhatri 於 https://github.com/flutter/flutter/pull/97350
• PointerDeviceKind 與 ui.PointerChange 前向相容 @moffatman 於 https://github.com/flutter/flutter/pull/97437
• 再次提交「支援 Scribble 手寫輸入 (#96615)」@fbcouch 於 https://github.com/flutter/flutter/pull/96736
• BottomNavigationBar: 新增可主題化滑鼠游標 @TahaTesser 於 https://github.com/flutter/flutter/pull/96597
• 修正 VisualDensity 的垂直 lerp 實作 @WasserEsser 於 https://github.com/flutter/flutter/pull/97245
• chore: 更新 AutofillContextAction 文件 @albertodev01 於 https://github.com/flutter/flutter/pull/97596
• 更新 gen_defaults 以使用 Material token 資料庫的新 JSON 輸出 @darrenaustin 於 https://github.com/flutter/flutter/pull/95593
• 允許 Clip.none 作為有效的 clipBehavior @Piinks 於 https://github.com/flutter/flutter/pull/92907
• 新增 DisplayFeatureSubScreen 元件 @andreidiaconu 於 https://github.com/flutter/flutter/pull/97677
• 更新 FAB 預設值，僅對計算值使用函式覆寫 @darrenaustin 於 https://github.com/flutter/flutter/pull/97673
• 新增橫向 scrollbar 文件 @Piinks 於 https://github.com/flutter/flutter/pull/97674
• 更新 SliverChildDelegate 文件 @Piinks 於 https://github.com/flutter/flutter/pull/97204
• TabBar 新增 splashBorderRadius @nayeemtby 於 https://github.com/flutter/flutter/pull/97446
• 重新排版時使 TextPainter 的行度量快取失效 @jason-simmons 於 https://github.com/flutter/flutter/pull/97171
• 修正 RouterObserver 在 reverseTransitionDuratio... 時未呼叫 didPop @chunhtai 於 https://github.com/flutter/flutter/pull/97705
• 修正 Local SwitchTheme 未被 Switch 元件繼承 @TahaTesser 於 https://github.com/flutter/flutter/pull/89451
• 清理 bindings API @Hixie 於 https://github.com/flutter/flutter/pull/97715
• 修正 Local CheckBoxTheme 未被 CheckBox 元件繼承 @TahaTesser 於 https://github.com/flutter/flutter/pull/97713
• 修正 Local RadioTheme 未被 Radio 元件繼承 @TahaTesser 於 https://github.com/flutter/flutter/pull/97763
• 修正 PopupMenuButton 範例標籤 @TahaTesser 於 https://github.com/flutter/flutter/pull/88470
• 準備 flutter.material.RawMaterialButton.mouseCursor 文件模板以支援可主題化滑鼠游標 @jpnurmi 於 ⟦L125⟧
• 文字編輯