我想在我的应用程序中添加方向箭头，使其看起来像this。有没有解决方案或建议？
答案 0 :(得分：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);
}
}
}
位图箭头在我的案例中位于顶部
答案 1 :(得分：0)
我的解决方案是搜索距离用户当前位置一定距离的感兴趣的地方（在这种情况下是咖啡店）。此距离可以是当前位置的北，南，东或西的“屏幕” - 屏幕距离将取决于您的缩放级别。不在当前屏幕上的商店将由屏幕边缘上的箭头表示，其方向设置在您当前的位置和商店之间。