Flutter 自定义 Google 地图标记信息窗口

我正在 Flutter 中研究 Google 地图标记。

单击每个标记时，我想显示一个自定义信息窗口，其中可以包含按钮、图像等。但是在 Flutter 中有一个属性TextInfoWindow只接受String.

我如何实现向地图标记添加按钮、图像InfoWindow.

偶然发现这个问题并找到了适合我的解决方案：

为了解决这个问题我写了一个自定义信息小部件 https://github.com/Menelphor/CustomInfoWidget/blob/master/custom_info_widget，随意定制。例如通过一些阴影剪辑阴影路径 https://gist.github.com/coman3/e631fd55cd9cdf9bd4efe8ecfdbb85a7.

执行

import 'dart:async';

import 'package:flutter/material.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';

import 'custom_info_widget.dart';

void main() => runApp(MyApp());

class PointObject {
  final Widget child;
  final LatLng location;

  PointObject({this.child, this.location});
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      initialRoute: "/",
      routes: {
        "/": (context) => HomePage(),
      },
    );
  }
}

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  PointObject point = PointObject(
    child:  Text('Lorem Ipsum'),
    location: LatLng(47.6, 8.8796),
  );

  StreamSubscription _mapIdleSubscription;
  InfoWidgetRoute _infoWidgetRoute;
  GoogleMapController _mapController;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(
        color: Colors.green,
        child: GoogleMap(
          initialCameraPosition: CameraPosition(
            target: const LatLng(47.6, 8.6796),
            zoom: 10,
          ),
          circles: Set<Circle>()
            ..add(Circle(
              circleId: CircleId('hi2'),
              center: LatLng(47.6, 8.8796),
              radius: 50,
              strokeWidth: 10,
              strokeColor: Colors.black,
            )),
          markers: Set<Marker>()
            ..add(Marker(
              markerId: MarkerId(point.location.latitude.toString() +
                  point.location.longitude.toString()),
              position: point.location,
              onTap: () => _onTap(point),
            )),
          onMapCreated: (mapController) {
            _mapController = mapController;
          },

          /// This fakes the onMapIdle, as the googleMaps on Map Idle does not always work
          /// (see: https://github.com/flutter/flutter/issues/37682)
          /// When the Map Idles and a _infoWidgetRoute exists, it gets displayed.
          onCameraMove: (newPosition) {
            _mapIdleSubscription?.cancel();
            _mapIdleSubscription = Future.delayed(Duration(milliseconds: 150))
                .asStream()
                .listen((_) {
              if (_infoWidgetRoute != null) {
                Navigator.of(context, rootNavigator: true)
                    .push(_infoWidgetRoute)
                    .then<void>(
                  (newValue) {
                    _infoWidgetRoute = null;
                  },
                );
              }
            });
          },
        ),
      ),
    );
  }
 /// now my _onTap Method. First it creates the Info Widget Route and then
  /// animates the Camera twice:
  /// First to a place near the marker, then to the marker.
  /// This is done to ensure that onCameraMove is always called 

  _onTap(PointObject point) async {
    final RenderBox renderBox = context.findRenderObject();
    Rect _itemRect = renderBox.localToGlobal(Offset.zero) & renderBox.size;

    _infoWidgetRoute = InfoWidgetRoute(
      child: point.child,
      buildContext: context,
      textStyle: const TextStyle(
        fontSize: 14,
        color: Colors.black,
      ),
      mapsWidgetSize: _itemRect,
    );

    await _mapController.animateCamera(
      CameraUpdate.newCameraPosition(
        CameraPosition(
          target: LatLng(
            point.location.latitude - 0.0001,
            point.location.longitude,
          ),
          zoom: 15,
        ),
      ),
    );
    await _mapController.animateCamera(
      CameraUpdate.newCameraPosition(
        CameraPosition(
          target: LatLng(
            point.location.latitude,
            point.location.longitude,
          ),
          zoom: 15,
        ),
      ),
    );
  }
}

自定义信息小部件：

import 'package:flutter/material.dart';
import 'package:flutter/painting.dart';
import 'package:meta/meta.dart';

class _InfoWidgetRouteLayout<T> extends SingleChildLayoutDelegate {
  final Rect mapsWidgetSize;
  final double width;
  final double height;

  _InfoWidgetRouteLayout(
      {@required this.mapsWidgetSize,
      @required this.height,
      @required this.width});

  /// Depending of the size of the marker or the widget, the offset in y direction has to be adjusted;
  /// If the appear to be of different size, the commented code can be uncommented and
  /// adjusted to get the right position of the Widget.
  /// Or better: Adjust the marker size based on the device pixel ratio!!!!)

  @override
  Offset getPositionForChild(Size size, Size childSize) {
//    if (Platform.isIOS) {
    return Offset(
      mapsWidgetSize.center.dx - childSize.width / 2,
      mapsWidgetSize.center.dy - childSize.height - 50,
    );
//    } else {
//      return Offset(
//        mapsWidgetSize.center.dx - childSize.width / 2,
//        mapsWidgetSize.center.dy - childSize.height - 10,
//      );
//    }
  }

  @override
  BoxConstraints getConstraintsForChild(BoxConstraints constraints) {
    //we expand the layout to our predefined sizes
    return BoxConstraints.expand(width: width, height: height);
  }

  @override
  bool shouldRelayout(_InfoWidgetRouteLayout oldDelegate) {
    return mapsWidgetSize != oldDelegate.mapsWidgetSize;
  }
}

class InfoWidgetRoute extends PopupRoute {
  final Widget child;
  final double width;
  final double height;
  final BuildContext buildContext;
  final TextStyle textStyle;
  final Rect mapsWidgetSize;

  InfoWidgetRoute({
    @required this.child,
    @required this.buildContext,
    @required this.textStyle,
    @required this.mapsWidgetSize,
    this.width = 150,
    this.height = 50,
    this.barrierLabel,
  });

  @override
  Duration get transitionDuration => Duration(milliseconds: 100);

  @override
  bool get barrierDismissible => true;

  @override
  Color get barrierColor => null;

  @override
  final String barrierLabel;

  @override
  Widget buildPage(BuildContext context, Animation<double> animation,
      Animation<double> secondaryAnimation) {
    return MediaQuery.removePadding(
      context: context,
      removeBottom: true,
      removeLeft: true,
      removeRight: true,
      removeTop: true,
      child: Builder(builder: (BuildContext context) {
        return CustomSingleChildLayout(
          delegate: _InfoWidgetRouteLayout(
              mapsWidgetSize: mapsWidgetSize, width: width, height: height),
          child: InfoWidgetPopUp(
            infoWidgetRoute: this,
          ),
        );
      }),
    );
  }
}

class InfoWidgetPopUp extends StatefulWidget {
  const InfoWidgetPopUp({
    Key key,
    @required this.infoWidgetRoute,
  })  : assert(infoWidgetRoute != null),
        super(key: key);

  final InfoWidgetRoute infoWidgetRoute;

  @override
  _InfoWidgetPopUpState createState() => _InfoWidgetPopUpState();
}

class _InfoWidgetPopUpState extends State<InfoWidgetPopUp> {
  CurvedAnimation _fadeOpacity;

  @override
  void initState() {
    super.initState();
    _fadeOpacity = CurvedAnimation(
      parent: widget.infoWidgetRoute.animation,
      curve: Curves.easeIn,
      reverseCurve: Curves.easeOut,
    );
  }

  @override
  Widget build(BuildContext context) {
    return FadeTransition(
      opacity: _fadeOpacity,
      child: Material(
        type: MaterialType.transparency,
        textStyle: widget.infoWidgetRoute.textStyle,
        child: ClipPath(
          clipper: _InfoWidgetClipper(),
          child: Container(
            color: Colors.white,
            padding: EdgeInsets.only(bottom: 10),
            child: Center(child: widget.infoWidgetRoute.child),
          ),
        ),
      ),
    );
  }
}

class _InfoWidgetClipper extends CustomClipper<Path> {
  @override
  Path getClip(Size size) {
    Path path = Path();
    path.lineTo(0.0, size.height - 20);
    path.quadraticBezierTo(0.0, size.height - 10, 10.0, size.height - 10);
    path.lineTo(size.width / 2 - 10, size.height - 10);
    path.lineTo(size.width / 2, size.height);
    path.lineTo(size.width / 2 + 10, size.height - 10);
    path.lineTo(size.width - 10, size.height - 10);
    path.quadraticBezierTo(
        size.width, size.height - 10, size.width, size.height - 20);
    path.lineTo(size.width, 10.0);
    path.quadraticBezierTo(size.width, 0.0, size.width - 10.0, 0.0);
    path.lineTo(10, 0.0);
    path.quadraticBezierTo(0.0, 0.0, 0.0, 10);
    path.close();
    return path;
  }

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