android - 我可以在 Google Maps Android 中画一条弯曲的虚线吗？

Question

在浏览器的 Google map 中，弯曲的虚线如下所示:

但是当我在自己的Android项目中实现Google Maps时，并没有显示这一行

如何画这条线？

Answer 1

您可以在两点之间实现曲线虚折线。为此，您可以使用 Google Maps Android API Utility Library具有 SphericalUtil 类并在您的代码中应用一些数学来创建折线。

你必须在你的 gradle 中包含实用程序库

编译 'com.google.maps.android:android-maps-utils:0.5'。

请查看我的示例 Activity 和函数 showCurvedPolyline (LatLng p1, LatLng p2, double k)，它在两点之间构造虚曲线折线。最后一个参数 k 定义折线的曲率，它可以是 >0 和 <=1。在我的示例中，我使用了 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

只需在 app/src/debug/res/values/google_maps_api.xml

中用您的 API key 替换我的 API key