在Android地图视图上画圆

问题描述 投票：17回答：4

搞定了这是我的解决方案。

编辑： 更新以反映Robguinness的答案。

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 android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Point;

public class CircleOverlay extends Overlay {

Context context;
double mLat;
double mLon;
float mRadius;

public CircleOverlay(Context _context, double _lat, double _lon, float radius ) {
    context = _context;
    mLat = _lat;
    mLon = _lon;
    mRadius = radius;
}

public CircleOverlay(Context _context, double _lat, double _lon, float radius ) {
    context = _context;
    mLat = _lat;
    mLon = _lon;
    mRadius = radius;
}

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

    if(shadow) return; // Ignore the shadow layer

    Projection projection = mapView.getProjection();

    Point pt = new Point();

    GeoPoint geo = new GeoPoint((int) (mLat *1e6), (int)(mLon * 1e6));

    projection.toPixels(geo ,pt);
    float circleRadius = projection.metersToEquatorPixels(mRadius) * (1/ FloatMath.cos((float) Math.toRadians(mLat)));

    Paint innerCirclePaint;

    innerCirclePaint = new Paint();
    innerCirclePaint.setColor(Color.BLUE);
    innerCirclePaint.setAlpha(25);
    innerCirclePaint.setAntiAlias(true);

    innerCirclePaint.setStyle(Paint.Style.FILL);

    canvas.drawCircle((float)pt.x, (float)pt.y, circleRadius, innerCirclePaint);
}

}

要 "绘制"，需要将其添加到地图的覆盖层中。

mMapView.getOverlays().add(new CircleOverlay(context, loc.getLatitude(),loc.getLongitude()));

希望能帮到你。

android android-mapview
4个回答
8
投票

接受的答案有一个错误。我试图纠正它，但由于一些奇怪的原因，我的编辑被拒绝。无论如何，这里是一个更正后的答案。

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 android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Point;

public class CircleOverlay extends Overlay {

    Context context;
    double mLat;
    double mLon;
    float mRadius;

    public CircleOverlay(Context _context, double _lat, double _lon, float radius ) {
        context = _context;
        mLat = _lat;
        mLon = _lon;
        mRadius = radius;
    }

    public CircleOverlay(Context _context, double _lat, double _lon, float radius ) {
        context = _context;
        mLat = _lat;
        mLon = _lon;
        mRadius = radius;
    }

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

        if(shadow) return; // Ignore the shadow layer

        Projection projection = mapView.getProjection();

        Point pt = new Point();

        GeoPoint geo = new GeoPoint((int) (mLat *1e6), (int)(mLon * 1e6));

        projection.toPixels(geo ,pt);
        float circleRadius = projection.metersToEquatorPixels(mRadius) * (1/ FloatMath.cos((float) Math.toRadians(mLat)));

        Paint innerCirclePaint;

        innerCirclePaint = new Paint();
        innerCirclePaint.setColor(Color.BLUE);
        innerCirclePaint.setAlpha(25);
        innerCirclePaint.setAntiAlias(true);

        innerCirclePaint.setStyle(Paint.Style.FILL);

        canvas.drawCircle((float)pt.x, (float)pt.y, circleRadius, innerCirclePaint);
    }
}

Scott的答案中的问题是 CircleRadius是用一种方法计算出来的，这种方法可以将点从米转换为像素。在赤道. 但是，如果你所需要的点不在赤道上，半径就会太小，因为换算没有考虑到经线在两极会合的事实。然而，这可以通过乘以 (1/ FloatMath.cos((float) Math.toRadians(mLat)))这是我对Scott的原始答案所做的唯一改动。

我希望这能帮助到别人，因为我发现了这个问题。我住在芬兰，用原来的方法，画出来的圆比应该画的小了2倍！我把上面的例子扩大，把需要画的圆考虑进去。

7
投票

我把上面的样本进行了扩展，考虑到了需要随着地图缩放水平而缩放的圆圈（即：相对于地面距离的圆圈）。

有些人可能会觉得它很有用。

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 android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Point;

public class CircleOverlay extends Overlay {

    Context context;
    double mLat;
    double mLon;
    float mRadius;

     public CircleOverlay(Context _context, double _lat, double _lon, float radius ) {
            context = _context;
            mLat = _lat;
            mLon = _lon;
            mRadius = radius;
     }

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

         if(shadow) return; // Ignore the shadow layer

         Projection projection = mapView.getProjection();

         Point pt = new Point();

         GeoPoint geo = new GeoPoint((int) (mLat *1e6), (int)(mLon * 1e6));

         projection.toPixels(geo ,pt);
         float circleRadius = projection.metersToEquatorPixels(mRadius) * (1/ FloatMath.cos((float) Math.toRadians(mLat)));

         Paint innerCirclePaint;

         innerCirclePaint = new Paint();
         innerCirclePaint.setColor(Color.BLUE);
         innerCirclePaint.setAlpha(25);
         innerCirclePaint.setAntiAlias(true);

         innerCirclePaint.setStyle(Paint.Style.FILL);

         canvas.drawCircle((float)pt.x, (float)pt.y, circleRadius, innerCirclePaint);
    }
}
0
投票

  1. 你想显示的地理点是（0.1275，51.507222）吗？这是在索马里海岸的某个地方。

  2. super.draw(..) 应该是你的第一句话。draw() 方法中添加以下代码。

0
投票

在方法中添加以下代码 onMapReady() 回调。

回调。

map.addCircle(new CircleOptions()
 .center(new LatLng(latitude, longitude))
 .radius(10000.0f)
 .strokeColor(Color.BLUE)
 .fillColor(Color.CYAN));

Kotlin

map.addCircle(CircleOptions()
 .center(LatLng(latitude, longitude))
 .radius(10000.0f)
 .strokeColor(Color.BLUE)
 .fillColor(Color.CYAN))
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