如何为 Qt Quick 解析 JSON

Question

我正在尝试进行简单的编程，将JSON消息值从web解析到Qt Quick。

JSON 消息想要解析：

[
    {
         "id": 2,
         "name": "yahoo",
         "link": "http://www.yahoo.com/",
         "created_by": "superadmin",
         "create_time": "2015-03-12 14:45:21"
    },
    {
         "id": 3,
         "name": "Google",
         "link": "http://www.google.com/",
         "created_by": "superadmin",
         "create_time": "2015-03-12 14:45:41"
    },
    {
         "id": 4,
         "name": "PS",
         "link": "http://www.playstation.com",
         "created_by": "superadmin",
         "create_time": "2015-03-24 11:57:21"
    }
]

以下是 Qt 代码 main.cpp 尝试解析这些数据：

#include <QGuiApplication>
#include <QStringList>
#include <QNetworkReply>
#include <QNetworkRequest>
#include <QNetworkAccessManager>
#include <QtScript/QScriptEngine>
#include <QtScript/QScriptValueIterator>
#include <QJsonDocument>
#include <QJsonObject>
#include <QJsonArray>
#include <qqmlengine.h>
#include <qqmlcontext.h>
#include <qqml.h>
#include <QtQuick/qquickitem.h>
#include <QtQuick/qquickview.h>
#include <main.h>

QStringList Jsondata::datalistmethod() {
   return datalist;
}

void Jsondata::onResult(QNetworkReply* reply)
{
    QString data = (QString) reply->readAll();

    QJsonDocument jsonResponse = QJsonDocument::fromJson(data.toUtf8());
    QJsonObject jsonObject = jsonResponse.object();

    foreach (const QJsonValue & value, jsonObject) {
        QJsonObject obj = value.toObject();
        datalist.append(obj["name"].toString());
        datalist.append(obj["link"].toString());
    }
}
int main(int argc, char ** argv)
{
    QGuiApplication app(argc, argv);
    Jsondata jsondata;
    // Now parse this JSON according to your needs !
   QNetworkAccessManager networkManager;
   networkManager.setNetworkAccessible(QNetworkAccessManager::Accessible);
   QUrl url("http://dbs.wasonicsystem.com/gta_test/api/web/v1/links");
   QNetworkRequest request;
   request.setUrl(url);
   Jsondata::connect(&networkManager, SIGNAL(finished(QNetworkReply*)), &jsondata, SLOT(onResult(QNetworkReply*)));
    networkManager.get(request);   // GET
    QStringList datalist;
    datalist = jsondata.datalistmethod();
    QQuickView view;
    QQmlContext *ctxt = view.rootContext();
    ctxt->setContextProperty("myModel", QVariant::fromValue(datalist));
    view.setSource(QUrl("qrc:main.qml"));
    view.show();
    return app.exec();
}

主H

#ifndef MAIN
#define MAIN
#include <QObject>
#include <QNetworkReply>
#include <QStringList>
class Jsondata : public QObject {
    Q_OBJECT
    QStringList datalist;
public slots:
    void onResult (QNetworkReply*);
public:
    QStringList datalistmethod();
};
#endif // MAIN

主.qml

import QtQuick 2.0
//![0]
ListView {
    width: 100; height: 100
    model: myModel
    delegate: Rectangle {
        height: 25
        width: 100
        Text { text: modelData }
    }
}
//![0]

结果：on结果仍未调用。所以没有返回数据列表

我对这个QObject::connect一无所知，也不知道出了什么问题。如果您能帮助我修复此错误，我将不胜感激。

Answer 1

我终于找到了解决问题的方法。以下是代码片段。

主.cpp

#include <QGuiApplication>
#include <QStringList>
#include <qqmlengine.h>
#include <qqmlcontext.h>
#include <qqml.h>
#include <QtQuick/qquickitem.h>
#include <QtQuick/qquickview.h>
#include <jsondata.h>
int main(int argc, char ** argv)
{
    QGuiApplication app(argc, argv);
    QStringList datalist;
    Jsondata jsondata;
    jsondata.datalistmethod();
    datalist = jsondata.datalist;
    QQuickView view;
    QQmlContext *ctxt = view.rootContext();
    ctxt->setContextProperty("myModel", QVariant::fromValue(datalist));
    view.setSource(QUrl("qrc:main.qml"));
    view.show();
    return app.exec();
}

jsondata.h

#ifndef JSONDATA_H
#define JSONDATA_H
#include <QObject>
#include <QNetworkReply>
#include <QStringList>
#include <QNetworkAccessManager>
class Jsondata : public QObject {
    Q_OBJECT
public:
    QStringList datalist;
    explicit Jsondata(QObject *parent =0);
    void datalistmethod();
public slots:
    void onResult (QNetworkReply*);
private:
    QNetworkAccessManager *manager;
};

jsondata.cpp

#include "jsondata.h"
#include <QNetworkReply>
#include <QNetworkRequest>
#include <QNetworkAccessManager>
#include <QJsonDocument>
#include <QJsonObject>
#include <QJsonArray>
#include <QEventLoop>
#include <QtQuick/qquickitem.h>
#include <QtQuick/qquickview.h>
#include <QTimer>
#include <qqmlengine.h>
#include <qqmlcontext.h>
#include <qqml.h>
Jsondata::Jsondata(QObject *parent) :
    QObject(parent)
{
}

void Jsondata::datalistmethod() {
    // Now parse this JSON according to your needs !
   manager = new QNetworkAccessManager(this);
   manager->setNetworkAccessible(QNetworkAccessManager::Accessible);
    QNetworkRequest request;
   QEventLoop eventloop;
   QUrl url("http://***/api/web/v1/links");
    request.setUrl(url);
     QNetworkReply *reply = manager->get(request);
   connect(reply, SIGNAL(finished()), &eventloop, SLOT(quit()));
   eventloop.exec();
   onResult(reply);
}

void Jsondata::onResult(QNetworkReply* reply)
{
    QString data = (QString) reply->readAll();
    qDebug() << "Response:" << data;
    QJsonDocument jsonResponse = QJsonDocument::fromJson(data.toUtf8());
    QJsonArray jsonArray = jsonResponse.array();
    foreach (const QJsonValue & value, jsonArray) {
        QJsonObject obj = value.toObject();
        datalist.append(obj["name"].toString());
        datalist.append(obj["link"].toString());
    }
}

通过添加事件循环，datalist 方法将等待 onResult 方法完成以执行下一行代码。这是使用字符串列表模型的示例。如果有人觉得它对参考有用，请+1我的帖子。 谢谢。^^