Android GIS开发系列-- 入门季（4） GraphicsLayer的点击查询要素

上一讲中我们学会了如何在MapView中添加Graphic要素，那么在百度或高德地图中，当我们点击要素时，会显示出相应的详细信息。在GraphicsLayer中也提供了这样的方法。下面我们来学习在GraphicsLayer中如何点击查找要素。 首先在MapView中添加两个Graphic要素。代码如下，注意这里用Graphic(Geometry geometry, Symbol symbol, Map<String, Object> attributes)来实例化Graphic，Map<String, Object> attributes是要素的属性值。详细见以下代码。TILED_WORLD_STREETS_URL为网络图层地址。

private void initLayer() {

        mapView.addLayer(new ArcGISTiledMapServiceLayer(
                TILED_WORLD_STREETS_URL));

        graphicsLayer = new GraphicsLayer();
        mapView.addLayer(graphicsLayer);

        Polygon polygon = new Polygon();
        polygon.startPath(new Point(1.2575908509778766E7,2879410.9266042486));
        polygon.lineTo(new Point(1.284360696117901E7,3021972.232083669));
        polygon.lineTo(new Point(1.2826182801620414E7,2713089.403544925));
        Map<String, Object> attr1 = new HashMap<>();
        attr1.put("name", "广州");
        attr1.put("mark", "广州是南方的城市");
        Graphic graphic1 = new Graphic(polygon, new SimpleFillSymbol(Color.RED),attr1);
        graphicsLayer.addGraphic(graphic1);


        Polygon polygon2 = new Polygon();
        polygon2.startPath(new Point(1.3388507951011453E7,3611225.628065273));
        polygon2.lineTo(new Point(1.3607101952746565E7,3858331.890896268));
        polygon2.lineTo(new Point(1.3613438010767872E7,3449656.14852193));
        Map<String, Object> attr2 = new HashMap<>();
        attr2.put("name", "上海");
        attr2.put("mark", "上海是中部的城市");
        Graphic graphic2 = new Graphic(polygon2, new SimpleFillSymbol(Color.GREEN),attr2);
        graphicsLayer.addGraphic(graphic2);



    }

效果图如下：

准备工作完成后，设置MapView的点击事件，

mapView.setOnSingleTapListener(new OnSingleTapListener() {

            @Override
            public void onSingleTap(float x, float y) {
                // TODO Auto-generated method stub
                handleSingleTap(x,y);
            }
        });

在handleSingleTap方法中来处理查询事件，GraphicsLayer查询要用到getGraphicIDs(float x, float y, int tolerance, int numberOfResults)或者getGraphicIDs(float x, float y, int tolerance)方法，前面两个参数是地图点击时的

x与y的值，tolerance是围绕x与y这个点所查询的范围，numberOfResults是要返回结果的大小。

/**
 * GraphicsLayer的点击查询
 * @param x
 * @param y
 */
protected void handleSingleTap(float x, float y) {

    int[] graphicIds = graphicsLayer.getGraphicIDs(x, y, 8);
    if (graphicIds!=null&&graphicIds.length>0) {
        for (int i = 0; i < graphicIds.length; i++) {
            Graphic graphic = graphicsLayer.getGraphic(graphicIds[i]);
            Map<String,Object> attr = graphic.getAttributes();
            Log.i(TAG, attr.get("name")+"===="+attr.get("mark"));
        }
    }
}这样当我们点击要素时，会打出以下的信息。