Reading multiple Xml Attributes with qml

问题

I've got and XML String in javascript (qml). My goal is to filter informations regarding different lines. I want an object containing the line name ( attribute) and especially the countdowns. For one line name there are departures_count * countdown fields. I want all these (in the current case its 2) countdown values in an array. And the ultimate goal is to load the whole line in a ListModel of the form: line(name, countdown(1,2,..x)).

The big problem is to access the attributes. In qml somehow the standard functions for the DOM tree are not supported: "Object has no such function as getAttribute()" and others aswell, like getElementByTagName(). With XmlListModel I can access attributes, but just if there is just one. In each other case it returns unknown (there is a bug in qt as far as I found out).

I allready tried pure XmlListModel, but had no luck (see: Parse XmlHttpRequest to XmlListModel) - there multiple entries are not supported. So I try to find a workarround:

To be processed XML:

<?xml version="1.0" encoding="UTF-8"?> 
<ft> 
  <response> 
    <client device="" appName="" clientId="123" appVersion=""/> 
    <responseType>api_get_monitor</responseType> 
    <responseTime>2011-05-31 14:41:13</responseTime> 
    <monitor id="36469" clientexpiration=""> 
      <lines count="24"> 
        <line name="U1" type="ptMetro" towards="Leopoldau" direction="H" platform="U1_H" barrierFree="1" realtimeSupported="1"> 
          <departures count="2"> 
            <departure> 
              <departureTime delay="" countdown="3"/> 
            </departure> 
            <departure> 
              <departureTime  delay="" countdown="6"/> 
            </departure> 
            <firstDeparture> 
              <departureTime  delay="" countdown=""/> 
            </firstDeparture> 
            <lastDeparture> 
              <departureTime  delay="" countdown=""/> 
            </lastDeparture> 
          </departures> 
        </line>
      </lines> 
    </monitor> 
    <trafficInfos/> 
    <message messageCode="1">ok</message> 
  </response> 
</ft> 

1 climbing the Object xml tree

With

 function getElementsByTagName(rootElement, tagName) {
        var childNodes = rootElement.childNodes;
        var elements = [];
        for(var i = 0; i < childNodes.length; i++) {
            if(childNodes[i].tagName === tagName) {
                elements.push(childNodes[i]);
            }
        }
        return elements;
    }

I can dig in to get the element line out of the whole xml tree.

attributeInterface.xml = depatures[0];
attributeInterface.query = "/"
attributeInterface.roles.name = "countdown";
attributeInterface.roles.query = "@countdown/string()";

and with this:

XmlListModel {
    id: attributeInterface

    onStatusChanged: {
        for (var i = 0; i < count; i++) {
            console.debug({"countdown": parseFloat(get(i).countdown) });
        }}}

I tried to get the attributes out. But the problem there is, that the assignment is invalid, because the xml-elements are objects (DOM? but the methods for such are not there..) and not text.

2 Regex

So my last bet, is to use regular expressions. Is there a way to get ALL countdown values? This is my best try, but it somehow just gets one value (i tried the + at the end to find all countdowns, but it wouldnt work. /delay\=\"\d*\".countdown\=\"(\d*)\"+/

And this for(var i = 0; i<5; i++) console.debug(found[i]); is how I retrieve the matches. The second iteration, so found[1] gives me 1 correct countdown. But how do I expand this concept to get all the countdowns?

回答1:

After searching and playing 2 days through, I got it. I hope this won't bother anyone anymore. There are 2 possible ways I found:

1 loopy loop

Or up the DomTree (number 1 in the org. question):

http://doc.qt.digia.com/qt-maemo/qdeclarativeglobalobject.html

This side was what I was looking for the whole time. It is bad documented (like everything I found about qml/qt), but has the one property one needs to read the attribute fields: attributes (note the typo in the link). It is an array of the attributes, so attributes[1].name is the name of the second att.

Thereafter I just need an easy way to climb the tree, which is described in the org. question.

2 XmlListModels

Since there is a depature count, one can fetch all these counts and then somehow fiddle together the countdowns (all in a list) and the respective lines (with the info how many counts for a line).

This is now just number 2, since if you don't got a hint how many attributes per node, this won't work. The order would go lost.

XmlListModel {
    id: lineXmlModel
    query: "/ft/response/monitor/lines/line"

    onStatusChanged: {
        if (status === 1) {
            console.debug("lineModel has: "+count+" items");
            for (var i = 0; i < count; i++) {
                lineListModel.append({"line": get(i).line});// , "depaturesCount": parseFloat(get(i).depaturesCount) });
            }
        }
    }

    // name = variable name, query fetches the data with XPATH
    XmlRole { name: "line"; query: "@name/string()" }

} // xmlModel



XmlListModel {
    id: depatureCountXmlModel
    query: "/ft/response/monitor/lines/line/departures"

    onStatusChanged: {
        if (status === 1) {
            console.debug("departureCountModel has: "+count+" items");
            for (var i = 0; i < count; i++) {
                lineListModel.append({"line": get(i).line, "depatureCount": parseFloat(get(i).depaturesCount) });
            }
        }
    }

    XmlRole { name: "depatureCount"; query: "@count/number()" }

} // xmlModel



XmlListModel {
    id: countdownXmlModel
    query: "/ft/response/monitor/lines/line/departures/departure/departureTime"

    onStatusChanged: {
        if (status === 1 && lineXmlModel.status === 1 && depatureCountXmlModel.status === 1) {
            console.debug("CountdownModel has: "+count+" items");
            for (var i = 0; i < lineXmlModel.count; i++) {
                console.debug("Line: "+ lineXmlModel.get(i).name + " number of depatures "+ depatureCountXmlModel.get(i).depatureCount );
                // console.debug("countdown "+ parseFloat(get(i).countdown) );
                // lineListModel.append({"countdown": parseFloat(get(i).countdown) });
            }
        }
    }

    XmlRole { name: "countdown"; query: "@countdown/number()" }
}

回答2:

Hi I do not know if that solves your problem. But I had similar problem and sovled it (related to your problem) like this. `

import QtQuick 2.0 
import QtQuick.XmlListModel 2.0


ListView 
{
  width: 300;
  height: 400; 

  spacing: 10 

  model: XmlListModel 
  {
    xml: '<?xml version="1.0" encoding="UTF-8"?> 
<ft> 
  <response> 
    <client device="" appName="" clientId="123" appVersion=""/> 
    <responseType>api_get_monitor</responseType> 
    <responseTime>2011-05-31 14:41:13</responseTime> 
    <monitor id="36469" clientexpiration=""> 
      <lines count="24"> 
    <line name="U1" type="ptMetro" towards="Leopoldau" direction="H" platform="U1_H" barrierFree="1" realtimeSupported="1"> 
      <departures count="2"> 
        <departure> 
          <departureTime delay="1" countdown="3"/> 
        </departure> 
        <departure> 
          <departureTime  delay="2" countdown="6"/> 
        </departure> 
        <firstDeparture> 
          <departureTime  delay="3" countdown="99"/> 
        </firstDeparture> 
        <lastDeparture> 
          <departureTime  delay="4" countdown="98"/> 
        </lastDeparture> 
      </departures> 
    </line>
      </lines> 
    </monitor> 
    <trafficInfos/> 
    <message messageCode="1">ok</message> 
  </response> 
</ft>'; 

    query:"/ft/response/monitor/lines/line/departures/departure"

    XmlRole { name:"delay" ; query: "departureTime/@delay/number()" } 
    XmlRole { name:"countdown" ; query: "departureTime/@countdown/number()" } 


  }

  delegate: 
  Rectangle
  {
    color: "pink"; 
    width:parent.width; 
    height: col.height
  Column 
  {
    id: col 
    Text{ text: countdown } 
    Text{ text: delay } 
  }
  }

}// listView `

来源：https://stackoverflow.com/questions/19281773/reading-multiple-xml-attributes-with-qml