Android：在OSM MapView上繪製多邊形（OSMDroid）

Question

是否可以在OSMDroid的mapview上繪製多邊形？它應該可以通過Mapview輕鬆擴展，所以我不想使用畫布。有什麼建議？ 我有我自己的MapOverlay（擴展org.osmdroid.views.overlay.Overlay），但無法得到我的Polygon。

Answer 1

如果類擴展org.osmdroid.views.overlay.Overlay必須修改draw方法，所以它看起來像某種方式在下面的代碼：

@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); 

}