Question

是否可以在OSMDroid的mapview上绘制多边形？它应该使用Mapview轻松扩展，所以我不想使用画布。有什么建议？我有自己的MapOverlay（扩展org.osmdroid.views.overlay.Overlay），但无法获取我的Polygon。

Answer 1

如果你的类正在扩展org.osmdroid.views.overlay.Overlay你必须修改draw方法，所以它看起来像下面的代码：

@Override
protected void draw(final Canvas canvas, final MapView mapView, final boolean shadow) {

       if (shadow) {
               return;
       }

       if (this.mPoints.size() < 2) {

        //Do nothing                    
        return;
       }

       final Projection pj = mapView.getProjection();

       // precompute new points to the intermediate projection.
       final int size = this.mPoints.size();

       while (this.mPointsPrecomputed < size) {
               final Point pt = this.mPoints.get(this.mPointsPrecomputed);
               pj.toMapPixelsProjected(pt.x, pt.y, pt);

               this.mPointsPrecomputed++;
       }

       Point screenPoint0 = null; // points on screen
       Point screenPoint1 = null;
       Point projectedPoint0; // points from the points list
       Point projectedPoint1;

       // clipping rectangle in the intermediate projection, to avoid performing projection.
       final Rect clipBounds = pj.fromPixelsToProjected(pj.getScreenRect());

       mPath.rewind();
       mPath.setFillType(Path.FillType.EVEN_ODD);
       projectedPoint0 = this.mPoints.get(size - 1);
       mLineBounds.set(projectedPoint0.x, projectedPoint0.y, projectedPoint0.x, projectedPoint0.y);

       for (int i = size - 2; i >= 0; i--) {
               // compute next points
               projectedPoint1 = this.mPoints.get(i);
               mLineBounds.union(projectedPoint1.x, projectedPoint1.y);

               if (!Rect.intersects(clipBounds, mLineBounds)) {
                       // skip this line, move to next point
                       projectedPoint0 = projectedPoint1;
                       screenPoint0 = null;
                       continue;
               }

               // the starting point may be not calculated, because previous segment was out of clip
               // bounds
               if (screenPoint0 == null) {
                       screenPoint0 = pj.toMapPixelsTranslated(projectedPoint0, this.mTempPoint1);
                       mPath.moveTo(screenPoint0.x, screenPoint0.y);
               }

               screenPoint1 = pj.toMapPixelsTranslated(projectedPoint1, this.mTempPoint2);

               // skip this point, too close to previous point
               if (Math.abs(screenPoint1.x - screenPoint0.x) + Math.abs(screenPoint1.y - screenPoint0.y) <= 1) {
                       continue;
               }

               mPath.lineTo(screenPoint1.x, screenPoint1.y);

               // update starting point to next position
               projectedPoint0 = projectedPoint1;
               screenPoint0.x = screenPoint1.x;
               screenPoint0.y = screenPoint1.y;
               mLineBounds.set(projectedPoint0.x, projectedPoint0.y, projectedPoint0.x, projectedPoint0.y);

       }

       mPath.close();
       canvas.drawPath(mPath, this.mPaint);

}

Android：在OSM MapView上绘制多边形（OSMDroid）

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