浮動AppBar中的textField焦點回滾問題解決
完整問題描述
SliverAppBar的floating=true,pinned=false模式中嵌套的TextField,會在獲取焦點時觸發CustomScrollView滾動到頂部。
問題表現
CustomScrollView和SliverAppBar的介紹和演示,參見官方文檔。
在floating=true和pinned=false 這兩個組合參數的模式下,SliverAppBar表現為:列表向上滑動時隨列表向上滑動直至消失。
列表在任何位置向下滑動時,會立即從上方滑入直至全部展現。
如果該組件內嵌套瞭TextField,在列表上滑一段距離,再下滑至SliverAppBar及其內嵌套的TextField出現時(此時列表尚未滑動到頂端),點擊TextField使其獲取焦點以輸入文字,此時列表會立即滾動至頂。
如圖:
初步探索
開始調試問題,嘗試瞭各種參數組合,隻要pinned為true就沒有這個問題,因為SliverAppBar總會展現在最頂端。然後想到瞭在獲取焦點的同時,將CustomScrollView的physics設置為 NeverScrollableScrollPhysics(意為禁止滾動),此時並不影響CustomScrollView的滾動位置,然後在輸入完成或失去焦點時,再取消禁止滾動的狀態,即可避免獲取焦點時列表滾動至頂端的問題。解決代碼如下:
class CustomScrollTextFieldPage extends StatefulWidget { const CustomScrollTextFieldPage({Key? key}) : super(key: key); @override State<CustomScrollTextFieldPage> createState() => _CustomScrollTextFieldPageState(); } class _CustomScrollTextFieldPageState extends State<CustomScrollTextFieldPage> { final textController = TextEditingController(); final editableTextController = TextEditingController(); bool focused = false; final focusNode = FocusNode(); final buttonFocus = FocusNode(); final textFocus = FocusNode(); @override void initState() { super.initState(); focusNode.addListener(_onFocus); } @override void dispose() { focusNode.removeListener(_onFocus); super.dispose(); } _onFocus() { setState(() { focused = focusNode.hasFocus; }); } @override Widget build(BuildContext context) { return Scaffold( body: GestureDetector( behavior: HitTestBehavior.translucent, onTapDown: () { FocusManager.instance.rootScope.requestFocus(FocusNode()); }, child: CustomScrollView( physics: focused ? const NeverScrollableScrollPhysics() : null, slivers: <Widget>[ SliverAppBar( floating: true, pinned: false, expandedHeight: 250.0, flexibleSpace: FlexibleSpaceBar( expandedTitleScale: 1, title: Row( crossAxisAlignment: CrossAxisAlignment.end, children: [ Expanded( child: TextField( focusNode: focusNode, controller: textController, onEditingComplete: () { FocusManager.instance.rootScope.requestFocus(FocusNode()); }, style: const TextStyle(color: Colors.white), decoration: const InputDecoration( border: UnderlineInputBorder( borderSide: BorderSide(color: Colors.white), ), focusedBorder: UnderlineInputBorder( borderSide: BorderSide(color: Colors.white), ), ), ), ), Padding( padding: EdgeInsets.symmetric(horizontal: 16), child: IconButton( visualDensity: VisualDensity(horizontal: 0, vertical: -4), padding: EdgeInsets.zero, onPressed: () { print('btn clicked'); buttonFocus.requestFocus(); }, focusNode: buttonFocus, icon: Icon(Icons.heart_broken), ), ) ], ), ), ), SliverGrid( gridDelegate: const SliverGridDelegateWithMaxCrossAxisExtent( maxCrossAxisExtent: 200.0, mainAxisSpacing: 10.0, crossAxisSpacing: 10.0, childAspectRatio: 4.0, ), delegate: SliverChildBuilderDelegate( (BuildContext context, int index) { return Container( alignment: Alignment.center, color: Colors.teal[100 * (index % 9)], child: Text('Grid Item $index'), ); }, childCount: 20, ), ), SliverFixedExtentList( itemExtent: 50.0, delegate: SliverChildBuilderDelegate( (BuildContext context, int index) { return Container( alignment: Alignment.center, color: Colors.lightBlue[100 * (index % 9)], child: Text('List Item $index'), ); }, ), ), ], ), ), ); } }
這個解決方法有點不完美的表現,就是輸入完成時不點擊頁面,而是直接點擊收起鍵盤,這時不會觸發onTapDown也不會觸發 onEditingComplete ,就需要在屏幕再點擊或者滑動時才能重置列表的可滾動狀態。
更好的解決辦法
經過進一步測試,發現在輸入框內的EditableText中對focus進行瞭監聽,在獲取焦點時遞歸調用瞭RenderObject的showOnScreen方法,會一直向上追溯Render樹,最終調用到RenderSliverList中,觸發瞭滾動事件。
是不是可以在TextField外包裹一個自定義瞭RenderBox的組件,把這個showOnScreen調用給切斷呢?於是翻瞭下官方的幾個組件寫法,照貓畫虎寫瞭個自定義的組件
class IgnoreShowOnScreenWidget extends SingleChildRenderObjectWidget { const IgnoreShowOnScreenWidget({ Key? key, Widget? child, this.ignoreShowOnScreen = true, }) : super(key: key, child: child); final bool ignoreShowOnScreen; @override RenderObject createRenderObject(BuildContext context) { return IgnoreShowOnScreenRenderObject( ignoreShowOnScreen: ignoreShowOnScreen, ); } } class IgnoreShowOnScreenRenderObject extends RenderProxyBox { IgnoreShowOnScreenRenderObject({ RenderBox? child, this.ignoreShowOnScreen = true, }); final bool ignoreShowOnScreen; @override void showOnScreen({ RenderObject? descendant, Rect? rect, Duration duration = Duration.zero, Curve curve = Curves.ease, }) { if (!ignoreShowOnScreen) { return super.showOnScreen( descendant: descendant, rect: rect, duration: duration, curve: curve, ); } } }
使用方法
class CustomScrollTextFieldPage extends StatefulWidget { const CustomScrollTextFieldPage({Key? key}) : super(key: key); @override State<CustomScrollTextFieldPage> createState() => _CustomScrollTextFieldPageState(); } class _CustomScrollTextFieldPageState extends State<CustomScrollTextFieldPage> { final textController = TextEditingController(); final focusNode = FocusNode(); @override Widget build(BuildContext context) { return Scaffold( body: GestureDetector( behavior: HitTestBehavior.translucent, onTap: () { FocusManager.instance.rootScope.requestFocus(FocusNode()); }, child: CustomScrollView( slivers: <Widget>[ SliverAppBar( floating: true, pinned: false, expandedHeight: 250.0, flexibleSpace: FlexibleSpaceBar( expandedTitleScale: 1, title: Row( crossAxisAlignment: CrossAxisAlignment.end, children: [ Expanded( child: IgnoreShowOnScreenWidget( child: TextField( focusNode: focusNode , controller: textController , style: const TextStyle(color: Colors.white), decoration: const InputDecoration( border: UnderlineInputBorder( borderSide: BorderSide(color: Colors.white), ), focusedBorder: UnderlineInputBorder( borderSide: BorderSide(color: Colors.white), ), ), ), ), ), Padding( padding: EdgeInsets.symmetric(horizontal: 16), child: IconButton( visualDensity: VisualDensity(horizontal: 0, vertical: -4), padding: EdgeInsets.zero, onPressed: () { print('btn clicked'); }, icon: Icon(Icons.heart_broken), ), ) ], ), ), ), SliverGrid( gridDelegate: const SliverGridDelegateWithMaxCrossAxisExtent( maxCrossAxisExtent: 200.0, mainAxisSpacing: 10.0, crossAxisSpacing: 10.0, childAspectRatio: 4.0, ), delegate: SliverChildBuilderDelegate( (BuildContext context, int index) { return Container( alignment: Alignment.center, color: Colors.teal[100 * (index % 9)], child: Text('Grid Item $index'), ); }, childCount: 20, ), ), SliverFixedExtentList( itemExtent: 50.0, delegate: SliverChildBuilderDelegate( (BuildContext context, int index) { return Container( alignment: Alignment.center, color: Colors.lightBlue[100 * (index % 9)], child: Text('List Item $index'), ); }, ), ), ], ), ), ); } }
初步嘗試,確實可以更方便地解決問題。
效果如圖:
目前還未發現有什麼副作用,如果哪位大神有更好的解決辦法,
以上就是浮動AppBar中的textField焦點回滾問題解決的詳細內容,更多關於AppBar浮動textField焦點回滾的資料請關註WalkonNet其它相關文章!
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