flutter-widget-offset

一个类库，用于获取和观察 widget 到根布局边缘的偏移量。 此类库也适用于对话框（showDialog）。

A class library for obtaining and listening the offset of the widget to the edge of the root layout. This type of library is also suitable for dialogs(showDialog).

Use OffsetDetector

Use OffsetDetector directly to get the offset of the widget to the edge of the root layout.

final OffsetDetectorController? _controller = OffsetDetectorController();

OffsetDetector(
  controller: _controller,
  onChanged: (Size size, EdgeInsets offset, EdgeInsets rootPadding) {
       print("The widget size: ${size.width}, ${size.height}");
       print(
           "The offset to edge of root(ltrb): ${offset.left}, ${offset.top}, ${offset.right}, ${offset.bottom}");
       print(
           "the root padding: ${rootPadding.left}, ${rootPadding.top}, ${rootPadding.right}, ${rootPadding.bottom}");
   },
  child: TextField(
    style: textFieldStyle,
    onChanged: (value) => _controller.notifyStateChanged(),
  ));

Use OffsetChangeObserver

Use OffsetChangeObserver to observe the offset of the widget to the edge of the root layout.

class OffsetDetector extends StatefulWidget {
  OffsetDetector({Key? key}) : super(key: key);

  @override
  State<StatefulWidget> createState() {
    return _OffsetDetectorState();
  }
}

class _OffsetDetectorState extends State<OffsetDetector>
    with WidgetsBindingObserver {
  late OffsetChangeObserver _observer;

  @override
  Widget build(BuildContext context) {
    return TextField();
  }

  void onChanged(Size size, EdgeInsets offset, EdgeInsets rootPadding) {
       print("The widget size: ${size.width}, ${size.height}");
       print(
           "The offset to edge of root(ltrb): ${offset.left}, ${offset.top}, ${offset.right}, ${offset.bottom}");
       print(
           "the root padding: ${rootPadding.left}, ${rootPadding.top}, ${rootPadding.right}, ${rootPadding.bottom}");
   }

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance!.addObserver(this);
    _observer =
        OffsetChangeObserver(context: context, onChanged: this.onChanged);
    _observer.onInitState();
  }

  @override
  void didChangeMetrics() {
    super.didChangeMetrics();
    _observer.onChangeMetrics();
  }

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    _observer.onChangeDependencies();
  }

  @override
  void dispose() {
    _observer.onDispose();
    WidgetsBinding.instance!.removeObserver(this);
    super.dispose();
  }
}

Example

see widget offset change example