如何在 Flutter 中自定义谷歌地图标记图标

Question

我在我的 flutter 应用程序中使用 google_maps_flutter 来使用谷歌地图我有自定义标记图标，我用 BitmapDescriptor.fromBytes(markerIcon) 加载它但我想用一些文本显示来自 Url 的图标。这是我的颤振代码：

Map<MarkerId, Marker> markers =
  <MarkerId, Marker>{}; // CLASS MEMBER, MAP OF MARKS

void _add([center]) async {


for (int i = 0; i < sallersList.length; i++) {
  if (sallersList[i]["uID"] != currentUser.uid) {
    /*var request = await http.get(sallersList[i]["user_image"]);
    var bytes = await request.bodyBytes;*/

     final Uint8List markerIcon = await getBytesFromCanvas(150,         150);

    var markerIdVal = sallersList[i]["uID"];
    final MarkerId markerId = MarkerId(markerIdVal);

    // creating a new MARKER
    final Marker marker = Marker(
      markerId: markerId,
      position: LatLng(
          sallersList[i]["latitude"], //+ sin(1 * pi / 6.0) / 20.0,
          sallersList[i]["longitude"] //+ cos(1 * pi / 6.0) / 20.0,
          ),
      // icon: BitmapDescriptor.fromBytes(bytes.buffer.asUint8List(),),
      icon: BitmapDescriptor.fromBytes(markerIcon),
      infoWindow: InfoWindow(
          title: sallersList[i]["user_name"],
          snippet: sallersList[i]["address"]),
      onTap: () {
       // print(sallersList[i]["uID"]);

        Navigator.of(context).push(new MaterialPageRoute(
            builder: (BuildContext context) =>
            new DirectDetails()));
      },
    );
    if (this.mounted)
      setState(() {
        // adding a new marker to map
        markers[markerId] = marker;
      });
  }
}
}


Future<Uint8List> getBytesFromCanvas(int width, int height) async  {
final ui.PictureRecorder pictureRecorder = ui.PictureRecorder();
final Canvas canvas = Canvas(pictureRecorder);
final Paint paint = Paint()..color = Colors.blue;
final Radius radius = Radius.circular(width/2);
canvas.drawRRect(
    RRect.fromRectAndCorners(
      Rect.fromLTWH(0.0, 0.0, width.toDouble(),  height.toDouble()),
      topLeft: radius,
      topRight: radius,
      bottomLeft: radius,
      bottomRight: radius,
    ),
    paint);

TextPainter painter = TextPainter(textDirection: TextDirection.ltr);
painter.text = TextSpan(
  text: '1',
  style: TextStyle(fontSize: 65.0, color: Colors.white),
);

painter.layout();
painter.paint(
    canvas,
    Offset((width * 0.5) - painter.width * 0.5,
        (height * .5) - painter.height * 0.5));
final img = await pictureRecorder.endRecording().toImage(width, height);
final data = await img.toByteData(format: ui.ImageByteFormat.png);
return data.buffer.asUint8List();
}

这就是我们想要达到的

这是我能够实现的。

是否有可能通过颤振或任何可以动态创建图像的外部图像依赖来实现相同的效果。

Answer 1

要实现上述造型休闲步骤如下：

1. 导入包

import 'dart:async';
import 'dart:ui' as ui;
import 'dart:typed_data';
import 'dart:io';
import 'package:flutter/material.dart';

2. （可选）添加辅助函数通过路径获取图片

Future<ui.Image> getImageFromPath(String imagePath) async {
    File imageFile = File(imagePath);

    Uint8List imageBytes = imageFile.readAsBytesSync();

    final Completer<ui.Image> completer = new Completer();

    ui.decodeImageFromList(imageBytes, (ui.Image img) {
      return completer.complete(img);
    });

    return completer.future;
}

3. 添加函数getMarkerIcon()返回BitmapDescriptor。这是您功能的替代品getBytesFromCanvas()

Future<BitmapDescriptor> getMarkerIcon(String imagePath, Size size) async {
    final ui.PictureRecorder pictureRecorder = ui.PictureRecorder();
    final Canvas canvas = Canvas(pictureRecorder);

    final Radius radius = Radius.circular(size.width / 2);

    final Paint tagPaint = Paint()..color = Colors.blue;
    final double tagWidth = 40.0;

    final Paint shadowPaint = Paint()..color = Colors.blue.withAlpha(100);
    final double shadowWidth = 15.0;

    final Paint borderPaint = Paint()..color = Colors.white;
    final double borderWidth = 3.0;

    final double imageOffset = shadowWidth + borderWidth;

    // Add shadow circle
    canvas.drawRRect(
        RRect.fromRectAndCorners(
          Rect.fromLTWH(
              0.0,
              0.0,
              size.width,
              size.height
          ),
          topLeft: radius,
          topRight: radius,
          bottomLeft: radius,
          bottomRight: radius,
        ),
        shadowPaint);

    // Add border circle
    canvas.drawRRect(
        RRect.fromRectAndCorners(
          Rect.fromLTWH(
              shadowWidth,
              shadowWidth,
              size.width - (shadowWidth * 2),
              size.height - (shadowWidth * 2)
          ),
          topLeft: radius,
          topRight: radius,
          bottomLeft: radius,
          bottomRight: radius,
        ),
        borderPaint);

    // Add tag circle
    canvas.drawRRect(
        RRect.fromRectAndCorners(
          Rect.fromLTWH(
              size.width - tagWidth,
              0.0,
              tagWidth,
              tagWidth
          ),
          topLeft: radius,
          topRight: radius,
          bottomLeft: radius,
          bottomRight: radius,
        ),
        tagPaint);

    // Add tag text
    TextPainter textPainter = TextPainter(textDirection: TextDirection.ltr);
    textPainter.text = TextSpan(
      text: '1',
      style: TextStyle(fontSize: 20.0, color: Colors.white),
    );

    textPainter.layout();
    textPainter.paint(
        canvas,
        Offset(
            size.width - tagWidth / 2 - textPainter.width / 2,
            tagWidth / 2 - textPainter.height / 2
        )
    );

    // Oval for the image
    Rect oval = Rect.fromLTWH(
        imageOffset,
        imageOffset,
        size.width - (imageOffset * 2),
        size.height - (imageOffset * 2)
    );

    // Add path for oval image
    canvas.clipPath(Path()
      ..addOval(oval));

    // Add image
    ui.Image image = await getImageFromPath(imagePath); // Alternatively use your own method to get the image
    paintImage(canvas: canvas, image: image, rect: oval, fit: BoxFit.fitWidth);

    // Convert canvas to image
    final ui.Image markerAsImage = await pictureRecorder.endRecording().toImage(
        size.width.toInt(),
        size.height.toInt()
    );

    // Convert image to bytes
    final ByteData byteData = await markerAsImage.toByteData(format: ui.ImageByteFormat.png);
    final Uint8List uint8List = byteData.buffer.asUint8List();

    return BitmapDescriptor.fromBytes(uint8List);
}

4. 像这样使用它

final Marker marker = Marker(
      icon: await getMarkerIcon("path/to/your/image.png", Size(150.0, 150.0))
);

注意： 出于演示目的，带有数字的标签被“松散”地定位 - 您可能需要对其进行不同的样式设置，以便它会随着内容而扩展。

Answer 2

1. 使用图像包，https://pub.dev/packages/image，如即时消息所示
2. 下载图像文件 f = wait _downloadFile(url, "border"); im.Image img = im.decodeImage(f.readAsBytesSync());
3. 使用drawString()在上面写数字
4. BitmapDescriptor.fromBytes(im.encodePng(img))

static var httpClient = new HttpClient();

Future<File> _downloadFile(String url, String filename) async {
    var request = await httpClient.getUrl(Uri.parse(url));
    var response = await request.close();
    var bytes = await consolidateHttpClientResponseBytes(response);
    String dir = (await getApplicationDocumentsDirectory()).path;
    File file = new File('$dir/$filename');
    await file.writeAsBytes(bytes);
    return file;
  }