xe5 delphi 解析 json

2014-03-04 17:35:41| 分类： mobile | 标签：delphi json mobile |举报 |字号大中小订阅

最简单的JSON大致像这样

{ "date":"周二(今天, 实时：12℃)", "dayPictureUrl":"http://api.map.baidu.com/images/weather/day/duoyun.png", "nightPictureUrl":"http://api.map.baidu.com/images/weather/night/duoyun.png", "weather":"多云", "wind":"北风微风", "temperature":"15 ~ 6℃" }

对于这种格式比较简单的json，解析是非常容易的

StrJson := RESTResponse1.Content; JSONObject := TJSONObject.ParseJSONValue(TEncoding.UTF8.GetBytes(StrJson), 0) as TJSONObject;

JSONObject.getValue('date'); 就可以得到date的值。如果像下面的这样结构比较复杂的json,就需要首先分析清楚这个json的格式才能获取成功。

{ "error":0, "status":"success", "date":"2014-03-04", "results": [ { "currentCity":"成都", "weather_data": [ { "date":"周二(今天, 实时：12℃)", "dayPictureUrl":"http://api.map.baidu.com/images/weather/day/duoyun.png", "nightPictureUrl":"http://api.map.baidu.com/images/weather/night/duoyun.png", "weather":"多云", "wind":"北风微风", "temperature":"15 ~ 6℃" } , { "date":"周三", "dayPictureUrl":"http://api.map.baidu.com/images/weather/day/yin.png", "nightPictureUrl":"http://api.map.baidu.com/images/weather/night/xiaoyu.png", "weather":"阴转小雨", "wind":"北风微风", "temperature":"14 ~ 7℃" } , { "date":"周四", "dayPictureUrl":"http://api.map.baidu.com/images/weather/day/xiaoyu.png", "nightPictureUrl":"http://api.map.baidu.com/images/weather/night/xiaoyu.png", "weather":"小雨", "wind":"北风微风", "temperature":"12 ~ 7℃" } , { "date":"周五", "dayPictureUrl":"http://api.map.baidu.com/images/weather/day/xiaoyu.png", "nightPictureUrl":"http://api.map.baidu.com/images/weather/night/xiaoyu.png", "weather":"小雨", "wind":"南风微风", "temperature":"9 ~ 6℃" } ] } ] }

这是一个嵌套结构，最外层是一个记录，包含"error", "status", "date", "results"四个字段，前三个都是简单的键值对，而“results”是一个数组，目前只有一个元素，即一条记录，这条记录的字段是"currentCity"和"weather_data"，再进一步"weather_data"又是一个组数，它有4个元素或者记录，每条记录里包含 "date"， "dayPictureUrl"，"nightPictureUrl"， "weather"，"wind"， "temperature"字段。

要想取出里面的"weather_data",利用目前的DBXJSON里的TJSONObject是不能直接取出来的，例如这样

StrJson := RESTResponse1.Content;
JSONObject := TJSONObject.ParseJSONValue(TEncoding.UTF8.GetBytes(StrJson), 0)
as TJSONObject;

weather := JSONObject.GetValue('weather_data');

需要一步一步的走，由于最外面是一个简单的json,可以先取出results,然后再取weather_data。

var JSONObject: TJSONObject; LItem: TJSONValue; LJPair: TJSONPair; weather: TJSONArray; StrJson: String; result: String; i: Integer;

begin

StrJson := 'xxxxxxx';//假定是上面那个json JSONObject := TJSONObject.ParseJSONValue(TEncoding.UTF8.GetBytes(StrJson), 0) as TJSONObject; JSONObject := (JSONObject.GetValue('results') as TJSONArray).Get(0) as TJSONObject; weather := JSONObject.GetValue('weather_data') as TJSONArray;
for i := 0 to weather.size - 1 do //应该是4条记录 begin LItem := (weather.Get(i) as TJSONObject).GetValue('weather'); //得到weather的值 result := result + '|' + LItem.Value; end; end

这段代码只是为了说明使用方法，没有做类型检查，最好在进行类型转换之前用is TJSONArray先判断是不是数组。