我可以在Google Maps Android中绘制弯曲的虚线吗？

Question

在具有弯曲虚线的浏览器的Google地图中,如下所示:

但是,当我在自己的Android项目中实施Google地图时,它并未显示此行

我怎么画这条线？

Answer 1

您可以在两点之间实现弯曲的虚线折线.为此,您可以使用具有SphericalUtil类的Google Maps Android API实用程序库,并在代码中应用一些数学运算来创建折线.

您必须将实用程序库包含在gradle中

compile 'com.google.maps.android:android-maps-utils:0.5'.

请查看我的示例活动和函数showCurvedPolyline (LatLng p1, LatLng p2, double k),它构建两点之间的虚线弯曲折线.最后一个参数k定义折线的曲率,它可以> 0且<= 1.在我的例子中,我使用k = 0.5

public class MapsActivity extends FragmentActivity implements OnMapReadyCallback {

private GoogleMap mMap;
private LatLng sydney1;
private LatLng sydney2;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_maps);
    // Obtain the SupportMapFragment and get notified when the map is ready to be used.
    SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
            .findFragmentById(R.id.map);
    mapFragment.getMapAsync(this);
}

@Override
public void onMapReady(GoogleMap googleMap) {
    mMap = googleMap;

    mMap.getUiSettings().setZoomControlsEnabled(true);

    // Add a marker in Sydney and move the camera
    sydney1 = new LatLng(-33.904438,151.249852);
    sydney2 = new LatLng(-33.905823,151.252422);

    mMap.addMarker(new MarkerOptions().position(sydney1)
            .draggable(false).visible(true).title("Marker in Sydney 1"));
    mMap.addMarker(new MarkerOptions().position(sydney2)
            .draggable(false).visible(true).title("Marker in Sydney 2"));

    mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(sydney1, 16F));

    this.showCurvedPolyline(sydney1,sydney2, 0.5);
}

private void showCurvedPolyline (LatLng p1, LatLng p2, double k) {
    //Calculate distance and heading between two points
    double d = SphericalUtil.computeDistanceBetween(p1,p2);
    double h = SphericalUtil.computeHeading(p1, p2);

    //Midpoint position
    LatLng p = SphericalUtil.computeOffset(p1, d*0.5, h);

    //Apply some mathematics to calculate position of the circle center
    double x = (1-k*k)*d*0.5/(2*k);
    double r = (1+k*k)*d*0.5/(2*k);

    LatLng c = SphericalUtil.computeOffset(p, x, h + 90.0);

    //Polyline options
    PolylineOptions options = new PolylineOptions();
    List<PatternItem> pattern = Arrays.<PatternItem>asList(new Dash(30), new Gap(20));

    //Calculate heading between circle center and two points
    double h1 = SphericalUtil.computeHeading(c, p1);
    double h2 = SphericalUtil.computeHeading(c, p2);

    //Calculate positions of points on circle border and add them to polyline options
    int numpoints = 100;
    double step = (h2 -h1) / numpoints;

    for (int i=0; i < numpoints; i++) {
        LatLng pi = SphericalUtil.computeOffset(c, r, h1 + i * step);
        options.add(pi);
    }

    //Draw polyline
    mMap.addPolyline(options.width(10).color(Color.MAGENTA).geodesic(false).pattern(pattern));
}

}

您可以从GitHub下载包含完整代码的示例项目

https://github.com/xomena-so/so43305664

只需用你的API替换我的API密钥 app/src/debug/res/values/google_maps_api.xml

Answer 2

当我用实线绘制曲线时，我遇到了同样的弯曲曲线问题。经过几个小时在互联网上搜索并尝试不同的解决方案。最后，我通过使用而不是提出了解决方案（不是正确的解决方案，但可以实现目标）。我修改了上面的方法来绘制平滑的曲线，并且曲线方向将始终向上。下面的截图是我修改后的版本的最终结果。PolygonPolylineshowCurvedPolyline()

fun drawCurveOnMap(googleMap: GoogleMap, latLng1: LatLng, latLng2: LatLng) {

    //Adding marker is optional here, you can move out from here.
    googleMap.addMarker(
       MarkerOptions().position(latLng1).icon(BitmapDescriptorFactory.defaultMarker()))
    googleMap.addMarker(
       MarkerOptions().position(latLng2).icon(BitmapDescriptorFactory.defaultMarker()))
    
    val k = 0.5 //curve radius
    var h = SphericalUtil.computeHeading(latLng1, latLng2)
    var d = 0.0
    val p: LatLng?

    //The if..else block is for swapping the heading, offset and distance 
    //to draw curve always in the upward direction
    if (h < 0) {
        d = SphericalUtil.computeDistanceBetween(latLng2, latLng1)
        h = SphericalUtil.computeHeading(latLng2, latLng1)
        //Midpoint position
        p = SphericalUtil.computeOffset(latLng2, d * 0.5, h)
    } else {
        d = SphericalUtil.computeDistanceBetween(latLng1, latLng2)

        //Midpoint position
        p = SphericalUtil.computeOffset(latLng1, d * 0.5, h)
    }

    //Apply some mathematics to calculate position of the circle center
    val x = (1 - k * k) * d * 0.5 / (2 * k)
    val r = (1 + k * k) * d * 0.5 / (2 * k)

    val c = SphericalUtil.computeOffset(p, x, h + 90.0)

    //Calculate heading between circle center and two points
    val h1 = SphericalUtil.computeHeading(c, latLng1)
    val h2 = SphericalUtil.computeHeading(c, latLng2)

    //Calculate positions of points on circle border and add them to polyline options
    val numberOfPoints = 1000 //more numberOfPoints more smooth curve you will get
    val step = (h2 - h1) / numberOfPoints

    //Create PolygonOptions object to draw on map
    val polygon = PolygonOptions()

    //Create a temporary list of LatLng to store the points that's being drawn on map for curve 
    val temp = arrayListOf<LatLng>()

    //iterate the numberOfPoints and add the LatLng to PolygonOptions to draw curve
    //and save in temp list to add again reversely in PolygonOptions
    for (i in 0 until numberOfPoints) {
        val latlng = SphericalUtil.computeOffset(c, r, h1 + i * step)
        polygon.add(latlng) //Adding in PolygonOptions
        temp.add(latlng)    //Storing in temp list to add again in reverse order
    }

    //iterate the temp list in reverse order and add in PolygonOptions
    for (i in (temp.size - 1) downTo 1) {
        polygon.add(temp[i])
    }

    polygon.strokeColor(Color.BLUE)
    polygon.strokeWidth(12f)
    polygon.strokePattern(listOf(Dash(30f), Gap(50f))) //Skip if you want solid line
    googleMap.addPolygon(polygon)

    temp.clear() //clear the temp list
}

为什么我们要在 PolygonOptions 中以相反的顺序再次添加临时列表？

如果我们不以相反的顺序LatLng再次添加PolygonOptions，则会googleMap.addPolygon()关闭路径，最终结果将如下所示。

尖端：

如果您希望曲线更呈圆形，请增加 的值k。喜欢k = 0.75

Answer 3

感谢@xomena 的精彩回答。但它只有一个小错误。有时，它的弧形变得像一个圆圈。我做了一些调试，看到，我们总是h + 90.0在方法的 12. 行使用标题值。我们可以通过像这样更改该行来解决这个问题：

LatLng c = SphericalUtil.computeOffset(p, x, h > 40 ? h + 90.0 : h - 90.0);

从现在开始，您可能不会再遇到此问题。