Flutter獲取點擊元素的位置與大小

使用 WidgetsBindingObserver獲取

class CloseTap extends StatefulWidget {
  @override
  _CloseTapTapState createState() => _CloseTapTapState();
}

class _CloseTapTapState extends State<CloseTap> with WidgetsBindingObserver {
  void _onAfterRendering(Duration timeStamp) {
    RenderObject renderObject = context.findRenderObject();
　　//獲取元素大小
    Size size = renderObject.paintBounds.size;
　　//獲取元素位置
    var vector3 = renderObject.getTransformTo(null)?.getTranslation();
    CommonUtils.showChooseDialog(context, size, vector3);
  }

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      child: Icon(Icons.close),
      onTapDown: (TapDownDetails details) {
        WidgetsBinding.instance.addPostFrameCallback(_onAfterRendering);
        setState(() {
        });
      },
    );
  }

　　目的是爲了實現如圖

在點擊X號的時候按照X號的位置進行位置計算

小三角是使用了Clip功能

Positioned(
                  left: dx - 10.0,
                  top: dy < h / 2 ? dy - wx / 2 : null,
                  bottom: dy < h / 2 ? null : (h - dy - wx / 2),
                  child: ClipPath(
                    clipper: Triangle(dir: dy - h / 2),
                    child: Container(
                      width: 30.0,
                      height: 30.0,
                      color: Colors.white,
                      child: null,
                    ),
                  ),
                ),

　　

class Triangle extends CustomClipper<Path> {
  double dir;
  Triangle({this.dir});
  @override
  Path getClip(Size size) {
    var path = Path();
    double w = size.width;
    double h = size.height;
    if (dir < 0) {
      path.moveTo(0, h);
      path.quadraticBezierTo(0, 0, w * 2 / 3, 0);
      path.quadraticBezierTo(w / 4, h / 2, w, h);
    } else {
      path.quadraticBezierTo(0, h / 2, w * 2 / 3, h);
      path.quadraticBezierTo(w / 3, h / 3, w, 0);
      path.lineTo(0, 0);
    }
    return path;
  }

  @override
  bool shouldReclip(CustomClipper<Path> oldClipper) => false;
}

　　

代碼部分見github項目      https://github.com/dnoyeb/syk_flutter