java - Android MapView方向箭头

Question

我想向我的应用程序添加方向箭头，使其看起来像 this .有什么解决方案或建议吗？

Answer 1

这是我的解决方案:

import android.content.Context;
import android.graphics.*;
import android.graphics.drawable.BitmapDrawable;
import android.util.Log;
import com.google.android.maps.GeoPoint;
import com.google.android.maps.MapView;
import com.google.android.maps.Overlay;
import com.google.android.maps.Projection;
import com.jettaxi.R;

import java.util.ArrayList;

public class ArrowDirectionsOverlay extends Overlay {
    private Context context;

    private ArrayList<GeoPoint> directions;
    private Bitmap arrowBitmap;
    private int maximalPositionX;
    private int maximalPositionY;

    public ArrowDirectionsOverlay(Context context) {
        this.context = context;

        directions = new ArrayList<GeoPoint>();

        arrowBitmap = BitmapFactory.decodeResource(context.getResources(), R.drawable.direction);
    }

    public void addDirectionPoint(GeoPoint destination) {
        directions.add(destination);
    }

    public void clear() {
        directions.clear();
    }

    private double getAngle(GeoPoint center, GeoPoint destination) {
        double lat1 = center.getLatitudeE6() / 1000000.;
        double lon1 = center.getLongitudeE6() / 1000000.;
        double lat2 = destination.getLatitudeE6() / 1000000.;
        double lon2 = destination.getLongitudeE6() / 1000000.;

        int MAXITERS = 20;
        // Convert lat/long to radians
        lat1 *= Math.PI / 180.0;
        lat2 *= Math.PI / 180.0;
        lon1 *= Math.PI / 180.0;
        lon2 *= Math.PI / 180.0;

        double a = 6378137.0; // WGS84 major axis
        double b = 6356752.3142; // WGS84 semi-major axis
        double f = (a - b) / a;
        double aSqMinusBSqOverBSq = (a * a - b * b) / (b * b);

        double L = lon2 - lon1;
        double A = 0.0;
        double U1 = Math.atan((1.0 - f) * Math.tan(lat1));
        double U2 = Math.atan((1.0 - f) * Math.tan(lat2));

        double cosU1 = Math.cos(U1);
        double cosU2 = Math.cos(U2);
        double sinU1 = Math.sin(U1);
        double sinU2 = Math.sin(U2);
        double cosU1cosU2 = cosU1 * cosU2;
        double sinU1sinU2 = sinU1 * sinU2;

        double sigma = 0.0;
        double deltaSigma = 0.0;
        double cosSqAlpha = 0.0;
        double cos2SM = 0.0;
        double cosSigma = 0.0;
        double sinSigma = 0.0;
        double cosLambda = 0.0;
        double sinLambda = 0.0;

        double lambda = L; // initial guess
        for (int iter = 0; iter < MAXITERS; iter++) {
            double lambdaOrig = lambda;
            cosLambda = Math.cos(lambda);
            sinLambda = Math.sin(lambda);
            double t1 = cosU2 * sinLambda;
            double t2 = cosU1 * sinU2 - sinU1 * cosU2 * cosLambda;
            double sinSqSigma = t1 * t1 + t2 * t2; // (14)
            sinSigma = Math.sqrt(sinSqSigma);
            cosSigma = sinU1sinU2 + cosU1cosU2 * cosLambda; // (15)
            sigma = Math.atan2(sinSigma, cosSigma); // (16)
            double sinAlpha = (sinSigma == 0) ? 0.0 :
                    cosU1cosU2 * sinLambda / sinSigma; // (17)
            cosSqAlpha = 1.0 - sinAlpha * sinAlpha;
            cos2SM = (cosSqAlpha == 0) ? 0.0 :
                    cosSigma - 2.0 * sinU1sinU2 / cosSqAlpha; // (18)

            double uSquared = cosSqAlpha * aSqMinusBSqOverBSq; // defn
            A = 1 + (uSquared / 16384.0) * // (3)
                    (4096.0 + uSquared *
                            (-768 + uSquared * (320.0 - 175.0 * uSquared)));
            double B = (uSquared / 1024.0) * // (4)
                    (256.0 + uSquared *
                            (-128.0 + uSquared * (74.0 - 47.0 * uSquared)));
            double C = (f / 16.0) *
                    cosSqAlpha *
                    (4.0 + f * (4.0 - 3.0 * cosSqAlpha)); // (10)
            double cos2SMSq = cos2SM * cos2SM;
            deltaSigma = B * sinSigma * // (6)
                    (cos2SM + (B / 4.0) *
                            (cosSigma * (-1.0 + 2.0 * cos2SMSq) -
                                    (B / 6.0) * cos2SM *
                                            (-3.0 + 4.0 * sinSigma * sinSigma) *
                                            (-3.0 + 4.0 * cos2SMSq)));

            lambda = L +
                    (1.0 - C) * f * sinAlpha *
                            (sigma + C * sinSigma *
                                    (cos2SM + C * cosSigma *
                                            (-1.0 + 2.0 * cos2SM * cos2SM))); // (11)

            double delta = (lambda - lambdaOrig) / lambda;
            if (Math.abs(delta) < 1.0e-12) {
                break;
            }
        }

        float distance = (float) (b * A * (sigma - deltaSigma));
        float initialBearing = (float) Math.atan2(cosU2 * sinLambda,
                cosU1 * sinU2 - sinU1 * cosU2 * cosLambda);
        initialBearing *= 180.0 / Math.PI;
        float finalBearing = (float) Math.atan2(cosU1 * sinLambda,
                -sinU1 * cosU2 + cosU1 * sinU2 * cosLambda);
        finalBearing *= 180.0 / Math.PI;

        return finalBearing;
    }

    private void drawArrow(Canvas canvas, MapView mapView, GeoPoint destination) {
        Point screenPts = mapView.getProjection().toPixels(destination, null);

        int deltaX = mapView.getMapCenter().getLatitudeE6() - destination.getLatitudeE6();
        int deltaY = mapView.getMapCenter().getLongitudeE6() - destination.getLongitudeE6();

        double angle = getAngle(mapView.getMapCenter(), destination);
        double tan = Math.tan(Math.toRadians(angle));

        Matrix matrix = new Matrix();
        matrix.postRotate((float) angle);
        Bitmap rotatedBmp = Bitmap.createBitmap(
                arrowBitmap,
                0, 0,
                arrowBitmap.getWidth(),
                arrowBitmap.getHeight(),
                matrix,
                true
        );

        int currentPositionX = screenPts.x - (rotatedBmp.getWidth() / 2);
        int currentPositionY = screenPts.y - (rotatedBmp.getHeight() / 2);

        if ((currentPositionX < 0) || (currentPositionY < 0) ||
                (currentPositionX > maximalPositionX) || (currentPositionY > maximalPositionY)) {

            int arrowPositionX = (int) (mapView.getWidth() / 2 - Math.signum(deltaX) * mapView.getHeight() / 2 * tan);
            arrowPositionX = Math.min(Math.max(arrowPositionX, 0), maximalPositionX);
            int arrowSpanX = (int) (mapView.getWidth() / 2.);

            int arrowPositionY = (int) (mapView.getHeight() / 2 + Math.signum(deltaY) * arrowSpanX / tan);
            arrowPositionY = Math.min(Math.max(arrowPositionY, 0), maximalPositionY);

            canvas.drawBitmap(
                    rotatedBmp,
                    arrowPositionX,
                    arrowPositionY,
                    null
            );
        }
    }

    public void draw(Canvas canvas, MapView mapView, boolean shadow) {
        super.draw(canvas, mapView, shadow);

        maximalPositionX = mapView.getWidth() - arrowBitmap.getWidth();
        maximalPositionY = mapView.getHeight() - arrowBitmap.getHeight();

        for (GeoPoint geoPoint : directions) {
            drawArrow(canvas, mapView, geoPoint);
        }
    }
}

在我的例子中位图箭头指向顶部