Flutter LatLngBounds 未显示准确的位置

Question

我正在尝试使用我的颤振谷歌地图将我的所有标记显示到视口中。但它似乎不适用于我的情况。到目前为止，我已经尝试过：

    _controller.animateCamera(CameraUpdate.newLatLngBounds(
            LatLngBounds(
              southwest: LatLng(23.785182, 90.330702),
              northeast: LatLng(24.582782, 88.821163),
            ),
            100
        ));

    LatLngBounds boundsFromLatLngList(List<LatLng> list) {
    assert(list.isNotEmpty);
    double x0, x1, y0, y1;
    for (LatLng latLng in list) {
      if (x0 == null) {
        x0 = x1 = latLng.latitude;
        y0 = y1 = latLng.longitude;
      } else {
        if (latLng.latitude > x1) x1 = latLng.latitude;
        if (latLng.latitude < x0) x0 = latLng.latitude;
        if (latLng.longitude > y1) y1 = latLng.longitude;
        if (latLng.longitude < y0) y0 = latLng.longitude;
      }
    }
    return LatLngBounds(northeast: LatLng(x1, y1), southwest: LatLng(x0, y0));
  }

正如我所见，它总是显示北大西洋的地图 有没有关于这个问题的解决方案，或者它刚刚在 Flutter 中开发？提前致谢

Answer 1

当我使用 CameraUpdate.newLatLngBounds 为地图制作动画时，我在 Android 上遇到了完全相同的问题（在 iOS 上运行良好）。它在设置边界后立即重新定位到北太平洋，不确定是什么原因造成的，但这里有一个解决方法 -

不用LatLngBounds设置地图位置，你可以计算你想要设置的边界的中心

// the bounds you want to set
LatLngBounds bounds = LatLngBounds(
  southwest: LatLng(23.785182, 90.330702),
  northeast: LatLng(24.582782, 88.821163),
);
// calculating centre of the bounds
LatLng centerBounds = LatLng(
  (bounds.northeast.latitude + bounds.southwest.latitude)/2,
  (bounds.northeast.longitude + bounds.southwest.longitude)/2
);

// setting map position to centre to start with
controller.moveCamera(CameraUpdate.newCameraPosition(CameraPosition(
  target: centerBounds,
  zoom: 17,
)));
zoomToFit(controller, bounds, centerBounds);

将地图位置设置为边界中心（并放大）后，您需要继续缩小，直到可见地图区域覆盖您要设置的边界。您可以使用controller.getVisibleRegion() 获取可见地图区域。这是实现 -

Future<void> zoomToFit(GoogleMapController controller, LatLngBounds bounds, LatLng centerBounds) async {
  bool keepZoomingOut = true;

  while(keepZoomingOut) {
    final LatLngBounds screenBounds = await controller.getVisibleRegion();
    if(fits(bounds, screenBounds)){
      keepZoomingOut = false;
      final double zoomLevel = await controller.getZoomLevel() - 0.5;
      controller.moveCamera(CameraUpdate.newCameraPosition(CameraPosition(
        target: centerBounds,
        zoom: zoomLevel,
      )));
      break;
    }
    else {
      // Zooming out by 0.1 zoom level per iteration
      final double zoomLevel = await controller.getZoomLevel() - 0.1;
      controller.moveCamera(CameraUpdate.newCameraPosition(CameraPosition(
        target: centerBounds,
        zoom: zoomLevel,
      )));
    }
  }
}

bool fits(LatLngBounds fitBounds, LatLngBounds screenBounds) {
  final bool northEastLatitudeCheck = screenBounds.northeast.latitude >= fitBounds.northeast.latitude;
  final bool northEastLongitudeCheck = screenBounds.northeast.longitude >= fitBounds.northeast.longitude;

  final bool southWestLatitudeCheck = screenBounds.southwest.latitude <= fitBounds.southwest.latitude;
  final bool southWestLongitudeCheck = screenBounds.southwest.longitude <= fitBounds.southwest.longitude;

  return northEastLatitudeCheck && northEastLongitudeCheck && southWestLatitudeCheck && southWestLongitudeCheck;
}

Answer 2

我遇到了同样的问题：

我并没有真正给出西南和东北坐标，但是： 西北和东南。 iOS 正常处理此问题，但 android 放大了大西洋。

修复后：

final highestLat = points.map((e) => e.latitude).reduce(max);
final highestLong = points.map((e) => e.longitude).reduce(max);
final lowestLat = points.map((e) => e.latitude).reduce(min);
final lowestLong = points.map((e) => e.longitude).reduce(min);

final lowestLatLowestLong = LatLng(lowestLat, lowestLong);
final highestLatHighestLong = LatLng(highestLat, highestLong);
final getRouteBoundsCameraUpdate = CameraUpdate.newLatLngBounds(LatLngBounds(southwest: lowestLatLowestLong, northeast: highestLatHighestLong), 25.0);

Answer 3

我也遇到了这个问题，尝试将southwest 值换成northeast 值

Answer 4

我发现这种方式非常适合我。

Future<void> updateCameraLocation(
  LatLng source,
  LatLng destination,
  GoogleMapController mapController,
) async {
  if (mapController == null) return;

  LatLngBounds bounds;

  if (source.latitude > destination.latitude &&
      source.longitude > destination.longitude) {
    bounds = LatLngBounds(southwest: destination, northeast: source);
  } else if (source.longitude > destination.longitude) {
    bounds = LatLngBounds(
        southwest: LatLng(source.latitude, destination.longitude),
        northeast: LatLng(destination.latitude, source.longitude));
  } else if (source.latitude > destination.latitude) {
    bounds = LatLngBounds(
        southwest: LatLng(destination.latitude, source.longitude),
        northeast: LatLng(source.latitude, destination.longitude));
  } else {
    bounds = LatLngBounds(southwest: source, northeast: destination);
  }

  CameraUpdate cameraUpdate = CameraUpdate.newLatLngBounds(bounds, 70);

  return checkCameraLocation(cameraUpdate, mapController);
}

Future<void> checkCameraLocation(
    CameraUpdate cameraUpdate, GoogleMapController mapController) async {
  mapController.animateCamera(cameraUpdate);
  LatLngBounds l1 = await mapController.getVisibleRegion();
  LatLngBounds l2 = await mapController.getVisibleRegion();

  if (l1.southwest.latitude == -90 || l2.southwest.latitude == -90) {
    return checkCameraLocation(cameraUpdate, mapController);
  }
}

并通过这一行使用：

await updateCameraLocation(source, destination, controller);