Android - Draw a path (array of points) in MapView

Although this post differs from my blog routine I am writing because I haven’t found an efficient way of displaying a list of GeoPoints to a MapView. This is often useful when you want to display directions from Google service inside your Android application.

Key features:

• A custom overlay that extends com.google.android.maps.Overlay
• Efficient way of displaying a path. The path is drawn over the same overlay.
• Smooth Lines, useful when there are a lot of corners like the example below
• Easy to use
• Easy to extend  - Just under 90 lines of code
• Available on Bitbucket

Here is a sample result of using my overlay to display a list of points (The green marker is not included).

You can use it like this

List<GeoPoint> path = new ArrayList<GeoPoint>();
//add your points somehow...
mapView.getOverlays().add(new RoutePathOverlay(path));

Here is the complete RoutePathOverlay.java (it's also available on Bitbucket)

import java.util.List;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.Point;
import android.graphics.RectF;
import com.google.android.maps.GeoPoint;
import com.google.android.maps.MapView;
import com.google.android.maps.Overlay;
import com.google.android.maps.Projection;
 
public class RoutePathOverlay extends Overlay {
 
        private int _pathColor;
        private final List<GeoPoint> _points;
        private boolean _drawStartEnd;
 
        public RoutePathOverlay(List<GeoPoint> points) {
                this(points, Color.RED, true);
        }
 
        public RoutePathOverlay(List<GeoPoint> points, int pathColor, boolean drawStartEnd) {
                _points = points;
                _pathColor = pathColor;
                _drawStartEnd = drawStartEnd;
        }
 
        private void drawOval(Canvas canvas, Paint paint, Point point) {
                Paint ovalPaint = new Paint(paint);
                ovalPaint.setStyle(Paint.Style.FILL_AND_STROKE);
                ovalPaint.setStrokeWidth(2);
                int _radius = 6;
                RectF oval = new RectF(point.x - _radius, point.y - _radius, point.x + _radius, point.y + _radius);
                canvas.drawOval(oval, ovalPaint);               
        }
 
        public boolean draw(Canvas canvas, MapView mapView, boolean shadow, long when) {
                Projection projection = mapView.getProjection();
                if (shadow == false && _points != null) {
                        Point startPoint = null, endPoint = null;
                        Path path = new Path();
                        //We are creating the path
                        for (int i = 0; i < _points.size(); i++) {
                                GeoPoint gPointA = _points.get(i);
                                Point pointA = new Point();
                                projection.toPixels(gPointA, pointA);
                                if (i == 0) { //This is the start point
                                        startPoint = pointA;
                                        path.moveTo(pointA.x, pointA.y);
                                } else {
                                        if (i == _points.size() - 1)//This is the end point
                                                endPoint = pointA;
                                        path.lineTo(pointA.x, pointA.y);
                                }
                        }
 
                        Paint paint = new Paint();
                        paint.setAntiAlias(true);
                        paint.setColor(_pathColor);
                        paint.setStyle(Paint.Style.STROKE);
                        paint.setStrokeWidth(5);
                        paint.setAlpha(90);
                        if (getDrawStartEnd()) {
                                if (startPoint != null) {
                                        drawOval(canvas, paint, startPoint);
                                }
                                if (endPoint != null) {
                                        drawOval(canvas, paint, endPoint);
                                }
                        }
                        if (!path.isEmpty())
                                canvas.drawPath(path, paint);
                }
                return super.draw(canvas, mapView, shadow, when);
        }
 
        public boolean getDrawStartEnd() {
                return _drawStartEnd;
        }
 
        public void setDrawStartEnd(boolean markStartEnd) {
                _drawStartEnd = markStartEnd;
        }
}

转帖：http://john.katsiotis.com/blog/android---draw-a-path-array-of-points-in-mapview