Question

我在Java中使用simpleJSON，我想创建一个geojson。我想循环一个列表，列表中的每个元素都有长度坐标，将为长线和纬度坐标创建一个数组。 geojson的格式应如下：

{"type": "FeatureCollection",
"crs": {
    "type": "name",
    "properties": {
            "name": "ESPG:4326"
            }
    },
    "features":[

    {
        "type":"Feature",
        "geometry":{
                "type":"Point",
                "coordinates":[55,55]
                },
        "properties":{
                "desc":"something"}
                }
    ]
},{
        "type":"Feature",
        "geometry":{
                "type":"Point",
                "coordinates":[49,32]
                },
        "properties":{
                "desc":"something"}
                }
    ]
}

我的问题是，当我循环遍历列表并且每次更改先前的值而不是仅添加新值时，.put用于JSONArray对象，所以我最终看起来像这样：

{"type": "FeatureCollection",
"crs": {
    "type": "name",
    "properties": {
            "name": "ESPG:4326"
            }
    },
    "features":[

    {
        "type":"Feature",
        "geometry":{
                "type":"Point",
                "coordinates":[55,55]
                },
        "properties":{
                "desc":"something"}
                }
    ]
},{
        "type":"Feature",
        "geometry":{
                "type":"Point",
                "coordinates":[55,55]
                },
        "properties":{
                "desc":"something"}
                }
    ]
}

以下是我正在使用的代码：

public String toJson(ArrayList<String> array){
  JSONObject featureCollection = new JSONObject();
  featureCollection.put("type", "FeatureCollection");
  JSONObject properties = new JSONObject();
  properties.put("name", "ESPG:4326");
  JSONObject crs = new JSONObject();
  crs.put("type", "name");
  crs.put("properties", properties);
  featureCollection.put("crs", crs);

  JSONArray features = new JSONArray();
  JSONObject feature = new JSONObject();
  feature.put("type", "Feature");
  JSONObject geometry = new JSONObject();

  JSONAray JSONArrayCoord = new JSONArray();
  for(int i=0; i<array.length; i++){
    eachElement = array[i];
    if(eachElement.getLongtitude()!=null){
      JSONArrayCoord.add(0, eachElement.getLongtitude());
      JSONArrayCoord.add(1, eachElement.getLatitude());
      geometry.put("type", "Point");
      geometry.put("coordinates", JSONArrayCoord);
      feature.put("geometry", geometry);

      features.add(feature);
      featureCollection.put("features", features);
    }
  }
  return featureCollection.toString();
}

有什么想法吗？谢谢!!

Answer 1

问题是我在循环外部初始化了一个名为feature，JSONArrayCoord和geometry的JSONObject。以下是for循环的更正代码：

for(int i=0; i<array.length; i++){
    eachElement = array[i];
    if(eachElement.getLongtitude()!=null){
      JSONObject geometry = new JSONObject();
      JSONArray JSONArrayCoord = new JSONArray();
      JSONObject newFeature = new JSONObject();

      JSONArrayCoord.add(0, eachElement.getLongtitude());
      JSONArrayCoord.add(1, eachElement.getLatitude());

      geometry.put("type", "Point");
      geometry.put("coordinates", JSONArrayCoord);
      feature.put("geometry", geometry);
      features.add(newFeature);
      featureCollection.put("features", features);
    }
  }

循环遍历列表并在Java中动态创建geoJSON

1 个答案: