只有当Widget发生结构变化,导致可滚动组件的State销毁或重新构建时才会丢失状态,这种情况就需要显式指定PageStorageKey,通过PageStorage来存储滚动位置,一个典型的场景是在使用TabBarView时,在Tab发生切换时,Tab页中的可滚动组件的State就会销毁,这时如果想恢复滚动位置就需要指定PageStorageKey。 ScrollPosition 真正保存滑动位...
crossAxisAlignment: CrossAxisAlignment.stretch, children: <Widget>[ Expanded( flex: 1, child: Container( color: Colors.blue, ), ), Expanded( flex: 2, child: getMyPatformView(), ), ], ), ); } Widget getMyPatformView() { if (defaultTargetPlatform == TargetPlatform.android) { return ...
通过 「CustomPaint」自定义或许是更好的选择; 2.尽可能使用const Widget,*为 Widget 提供const构造方法; 3.可以将「Stateless Widget」重构成「Stateful Widget」,*以便可以使用「Stateful Widget」中一些特定的优化手法,如:缓存「sub trees」的公共部分,并在改变树结构时使用GlobalKey; 4.尽量减小 rebuilt...
// 如果偏移量大于 (当前cell顶部与视口顶部之间的距离), 则当前cell靠上对齐滚入屏幕内(cell上边已经超出视口)if(position.pixels > viewport.getOffsetToReveal(object,0.0).offset) {//Move down to the top of the viewportalignment =0.0; // 如果偏移量小于 (当前cell底部与视口底部之间的距离, 可能为负...
[ Widget Preview ] Invalidate scaffold project if SDK changes and regenerate pubspec on change #163343 merged Feb 19, 2025 Hot Restart should dispose all previous Platform Views (macOS) #163439 merged Feb 19, 2025 Remove duplicate sources in the web_sdk. #163636 merged Feb 19, 2025 ...
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children:<Widget>[ _image==null? Text("未选择图片"): Image.file(_image), RaisedButton( child: Text("选择照片"), onPressed: _pickImage, ) ], ), ), ); }void_pickImage() async { File image=await ImagePicker.pickImage(source: ImageSource.gallery); ...
('While the widget tree was being built, laid out, and painted, ''a new frame was scheduled to rebuild the widget tree.',),ErrorHint('This might be because setState() was called from a layout or ''paint callback. ''If a change is needed to the widget tree, it should be applied...
Widgetbuild(BuildContext context){final screenWidth=MediaQuery.of(context).size.width;constbreakpoint=600.0;if(screenWidth>=breakpoint){// widescreen: menu on the left, content on the rightreturnRow(children:[// use SizedBox to constrain the AppMenu to a fixed widthSizedBox(width:240,// TODO...
Widget_buildContextMenu(BuildContext context,EditableTextState state){final TextEditingValue value=state.textEditingValue;final List<ContextMenuButtonItem>buttonItems=state.contextMenuButtonItems;String selectValue=value.selection.textInside(value.text);if(isValidEmail(selectValue)){buttonItems.insert(0,Cont...