Question

我想在SimpleFeatureCollection上做一个嵌套循环。对于每个点我都需要找到它的neihgbours并处理它们。

但是，SimpleFeatureCollection只允许迭代器，但不允许数组访问，这使得实现嵌套循环变得不可能（至少看起来如此）。这个迭代器没有previous（）方法，所以我无法重置它并在同一个集合中使用两个迭代器。

所以我想知道是否有其他方法可以通过索引访问功能。

由于

Answer 1

这里有一个代码示例： http://docs.geotools.org/latest/userguide/library/main/collection.html#join

它显示了如何嵌套循环：

void polygonInteraction() {
    SimpleFeatureCollection polygonCollection = null;
    SimpleFeatureCollection fcResult = null;
    final SimpleFeatureCollection found = FeatureCollections.newCollection();

    FilterFactory2 ff = CommonFactoryFinder.getFilterFactory2();
    SimpleFeature feature = null;

    Filter polyCheck = null;
    Filter andFil = null;
    Filter boundsCheck = null;

    String qryStr = null;

    SimpleFeatureIterator it = polygonCollection.features();
    try {
        while (it.hasNext()) {
            feature = it.next();
            BoundingBox bounds = feature.getBounds();
            boundsCheck = ff.bbox(ff.property("the_geom"), bounds);

            Geometry geom = (Geometry) feature.getDefaultGeometry();
            polyCheck = ff.intersects(ff.property("the_geom"), ff.literal(geom));

            andFil = ff.and(boundsCheck, polyCheck);

            try {
                fcResult = featureSource.getFeatures(andFil);
                // go through results and copy out the found features
                fcResult.accepts(new FeatureVisitor() {
                    public void visit(Feature feature) {
                        found.add((SimpleFeature) feature);
                    }
                }, null);
            } catch (IOException e1) {
                System.out.println("Unable to run filter for " + feature.getID() + ":" + e1);
                continue;
            }

        }
    } finally {
        it.close();
    }
}

如果您想忽略已访问过的某些功能，请跳过内容::

HashSet<FeatureId> skip = new HashSet<FeatureId>();
...
if( skip.contains( feature.getId() ) ) continue;

Answer 2

通常，只要它们只是读取而不是修改集合，就可以在集合上有多个迭代器。请参阅this question。

我希望SimpleFeatureCollection不是规则的例外！

对于嵌套循环，您可以通过内部循环为每次运行创建另一个迭代器;你不需要“重置”前一个。

Geotools嵌套在SimpleFeatureCollection上的循环

2 个答案: