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【Qt】XML


【目的】

  • 讀取 Google Weather。

【原理】

  • Google Weather 提供多樣化的API查詢方式
  • Xml 結點與資料(1)
    • 透過 WMHelp XMLPad Pro Edition 與 XMLmind XML Editor檢視。
      明顯可以看出左邊的圖分類的非常清楚。
      imageimage
    • 同事試過亦可由 FreeMind 讀取XML 資料(透過 PS Pad 整理縮排後)
  • Xml 結點與資料(2)，以 2010年 9月 29 日(禮拜三)為例
    • xml_api_reply version=1 (第一層)
      • weather module_id=0 tab_id=0 mobile_row=0 mobile_zipped=1 row=0 section=0
        • forecast_information 預測資料 (第三層)
          • city data=taipei (第四層)
          • postal_code data=taipei
          • latitude_e6 data=
          • forecast_date=2010-09-29
          • current_date_time data=2010-09-29 14:00:00 +0000
          • unit_system data=SI
        • current_conditions 目前狀況 ( 猜測是代表目前時間，比如說 11:00am時的天氣)
          • condition data=多雲
          • temp_f data=79
          • temp_c data=26
          • humidity data=濕度： 86%
          • icon data=/ig/images/weather/cloudy.gif
          • wind_condition data=風向： 公里/小時
        • forecast_conditions 預測狀況(這周的天氣預測)
          • day_of_week data=週三
          • low data=23
          • high data=28
          • icon data=/ig/images/weather/rain.gif
          • condition data=多雲時陰短暫雨
        • forecast_conditions 預測狀況
          • day_of_week data=週四
          • low data=23
          • high data=29
          • icon data=/ig/images/weather/rain.gif
          • condition data=多雲短暫雨
        • forecast_conditions 預測狀況
          • day_of_week data=週五
          • low data=24
          • high data=32
          • icon data=/ig/images/weather/cloudy.gif
          • condition data=多雲
        • forecast_conditions 預測狀況
          • day_of_week data=週六
          • low data=24
          • high data=33
          • icon data=/ig/images/weather/cloudy.gif
          • condition data=多雲
  • Xml 格式資料可透過幾種方式讀取
    • SAX(Simple API for XML)  XML資料唯獨，讀取速度較快
    • DOM(Document Object Model)  可更新 XML 資料
    • Pull Parse(Java推薦方式，目前Qt 不支援)

【程式】

  1. main.c  一樣用之前的 QHttp 範例，main.c 中有兩個地方需特別注意
    1. 抓取資料的網址改成由原本的zh_tw以us顯示，方便處理 
      http://www.google.com/ig/api?hl=us&weather=taipei
    2. 抓取網頁成功之後的callback function binding 到 show_weather 
      int main(int argc, char *argv[])
{
  QApplication a(argc, argv);
  Dialog w;
  w.show();

  HttpGet getter;
  QUrl url("http://www.google.com/ig/api?hl=us&weather=taipei");
  getter.downloadFile(QUrl(url));
  QObject::connect(&getter, SIGNAL(finished()), &w, SLOT(show_weather()));

    return a.exec();
}

  2. 由於我們不需更改資料，所以以 SAX 先作實驗
    (tbd)

  3. 透過 DOM 的方式 (通常可用 QTreeWidgetItem搭配遞迴方式載入，此處使用苦工方式一個一個讀出)

    1. dialog.h 

      #ifndef DIALOG_H
#define DIALOG_H

#include <QDialog>
#include <QUrl>
#include "HttpGet.h"
#include <iostream>
#include <QtXml>
#include <QFile>

namespace Ui {
    class Dialog;
}
class Dialog : public QDialog {
    Q_OBJECT
public:
    Dialog(QWidget *parent = 0);
    ~Dialog();
protected:
    void changeEvent(QEvent *e);
private:
    Ui::Dialog *ui;
private slots:
    void show_weather();
    void show_forecast_information(const QDomNode node3);
    void show_current_conditions(const QDomNode node3);
    void show_forecast_conditions(const QDomNode node3);
};

#endif // DIALOG_H

    2. dialog.cpp 

      void Dialog::show_weather()
{
    QDomDocument doc;
    QFile file("api");
    QString errorStr;
    int errorLine;
    int errorCol;
    if(!doc.setContent(&file,true,&errorStr,&errorLine,&errorCol)){
        qDebug() << "Unable to open the file";
        return;
    }
    file.close();

    QDomElement root = doc.documentElement();
    if (root.tagName() != "xml_api_reply")
        return;

    QDomNode node2 = root.firstChild();
    if(node2.toElement().tagName() == "weather")
    {
        QDomNode node3 = node2.firstChild();
           while (!node3.isNull()){
            qDebug() << "-" << node3.toElement().tagName();
            if(node3.toElement().tagName() == "forecast_information")
                show_forecast_information(node3);
            else if (node3.toElement().tagName() == "current_conditions")
                show_current_conditions(node3);
            else if (node3.toElement().tagName() == "forecast_conditions")
                show_forecast_conditions(node3);
            node3 = node3.nextSibling();
           }
        }
}
void Dialog::show_forecast_information(const QDomNode node3)
{
    QDomNode node4 = node3.firstChild();
    while (!node4.isNull()){
        if(node4.toElement().tagName() == "city")
            qDebug() << "    +city:" << node4.toElement().attribute("data");
        else if(node4.toElement().tagName() == "postal_code")
            qDebug() << "    +postal_code:" << node4.toElement().attribute("data");
        else if(node4.toElement().tagName() == "latitude_e6")
            qDebug() << "    +latitude_e6:" << node4.toElement().attribute("data");
        else if(node4.toElement().tagName() == "forecast_date")
            qDebug() << "    +forecast_date:" << node4.toElement().attribute("humidity");
        else if(node4.toElement().tagName() == "current_date_time")
            qDebug() << "    +current_date_time:" << node4.toElement().attribute("data");
        else if(node4.toElement().tagName() == "unit_system")
            qDebug() << "    +unit_system:" << node4.toElement().attribute("data");
        node4 = node4.nextSibling();
    }
}
void Dialog::show_current_conditions(const QDomNode node3)
{  
    QDomNode node4 = node3.firstChild();
    while (!node4.isNull()){
        if(node4.toElement().tagName() == "condition")
            qDebug() << "    +condition:" << node4.toElement().attribute("data");
        else if(node4.toElement().tagName() == "temp_f")
            qDebug() << "    +temp_f:" << node4.toElement().attribute("data");
        else if(node4.toElement().tagName() == "temp_c")
            qDebug() << "    +temp_c:" << node4.toElement().attribute("data");
        else if(node4.toElement().tagName() == "humidity")
            qDebug() << "    +humidity:" << node4.toElement().attribute("humidity");
        else if(node4.toElement().tagName() == "icon")
            qDebug() << "    +icon:" << node4.toElement().attribute("data");
        else if(node4.toElement().tagName() == "wind_condition")
            qDebug() << "    +wind_condition:" << node4.toElement().attribute("data");
        node4 = node4.nextSibling();
    }
}
void Dialog::show_forecast_conditions(const QDomNode node3)
{
    QDomNode node4 = node3.firstChild();
    while (!node4.isNull()){
        if(node4.toElement().tagName() == "day_of_week")
            qDebug() << "    +day_of_week:" << node4.toElement().attribute("data");
        else if(node4.toElement().tagName() == "low")
            qDebug() << "    +low:" << node4.toElement().attribute("data");
        else if(node4.toElement().tagName() == "high")
            qDebug() << "    +high:" << node4.toElement().attribute("data");
        else if(node4.toElement().tagName() == "icon")
            qDebug() << "    +icon:" << node4.toElement().attribute("data");
        else if(node4.toElement().tagName() == "condition")
            qDebug() << "    +condition:" << node4.toElement().attribute("data");
        node4 = node4.nextSibling();
    }
}
    3. 結果 
      - "forecast_information" 
    +city: "taipei" 
    +postal_code: "taipei" 
    +latitude_e6: "" 
    +forecast_date: "" 
    +current_date_time: "2010-09-29 23:00:00 +0000" 
    +unit_system: "US" 
- "current_conditions" 
    +condition: "Clear" 
    +temp_f: "82" 
    +temp_c: "28" 
    +humidity: "" 
    +icon: "/ig/images/weather/sunny.gif" 
    +wind_condition: "Wind:  mph" 
- "forecast_conditions" 
    +day_of_week: "Thu" 
    +low: "75" 
    +high: "87" 
    +icon: "/ig/images/weather/rain.gif" 
    +condition: "Rain" 
- "forecast_conditions" 
    +day_of_week: "Fri" 
    +low: "77" 
    +high: "89" 
    +icon: "/ig/images/weather/cloudy.gif" 
    +condition: "Cloudy" 
- "forecast_conditions" 
    +day_of_week: "Sat" 
    +low: "77" 
    +high: "91" 
    +icon: "/ig/images/weather/cloudy.gif" 
    +condition: "Cloudy" 
- "forecast_conditions" 
    +day_of_week: "Sun" 
    +low: "73" 
    +high: "86" 
    +icon: "/ig/images/weather/rain.gif" 
    +condition: "Rain"

【其它】

【參考】

 

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