51.Qt-使用ajax获取ashx接口的post数据

由于当前C++项目需要使用ajax库去post调用ashx接口,接口地址如下所示:

需要传递的参数如下:

然后发现qml比较好调用ajax.js库,所以本章通过C++界面去获取qml方法来实现调用ashx接口(以一个C++界面demo程序为例)

 1.抓post数据

通过网页获取到的post数据如下所示:

所以查询20191121~20191122期间时则填入内容: "deptCode=021&startDate=20191121&endDate=20191122"

2.导入ajax.js库

ajax.js文件如下所示:

// GET
function get(url, success, failure)
{
    var xhr = new XMLHttpRequest;
    xhr.open("GET", url);
    xhr.onreadystatechange = function() {
        handleResponse(xhr, success, failure);
    }
    xhr.send();
}

// POST
function post(url, arg, success, failure)
{
    var xhr = new XMLHttpRequest;
    xhr.open("POST", url);
    xhr.setRequestHeader("Content-Length", arg.length);
    xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded;");  //用POST的时候一定要有这句
    xhr.onreadystatechange = function() {
        handleResponse(xhr, success, failure);
    }
    xhr.send(arg);
}

// 处理返回值
function handleResponse(xhr, success, failure){
    if (xhr.readyState == XMLHttpRequest.DONE) {
        if (xhr.status ==  ){
            if (success != null && success != undefined)
            {
                var result = xhr.responseText;
                try{
                    success(result, JSON.parse(result));
                }catch(e){
                    success(result, {});
                }
            }
        }
        else{
            if (failure != null && failure != undefined)
                failure(xhr.responseText, xhr.status);
        }
    }
}

3.写main.qml

import QtQuick 2.3
import QtQuick.Window 2.2
import "ajax.js" as Ajax
Item {

    function getWrenchTools(deptCode,startDate,endDate) {
        console.log("Got message:", deptCode,startDate,endDate) //打印参数数据

Ajax.post("http://10.194.102.253/WLPTService/Pages/Tools/GetNLToolsByDeptCode.ashx","deptCode="+deptCode+"&startDate="+startDate+"&endDate="+endDate+"",
                  Widget.invokeFunc);

}

这里表示定义一个getWrenchTools()方法,当post成功并返回数据时,则调用Widget.invokeFunc()回调函数(Widget: 该qml对应的C++类,后面会讲怎么捆绑的)

4.widget界面如下

然后写widget.h

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <QString>
#include <QDebug>
#include <QTimer>
#include <QQmlApplicationEngine>
#include <QQmlComponent>
namespace Ui {
class widget;
}

class widget : public QWidget
{
    Q_OBJECT

    QQmlApplicationEngine engine;
    QObject *engineObject;      //指向运行的qml对象

public:
    explicit widget(QWidget *parent = );
    ~widget();

private:
    Ui::widget *ui;

public:
     Q_INVOKABLE void invokeFunc(QVariant data1,QVariant data2);   

private slots:
    void on_pushButton_clicked();
};

#endif // WIDGET_H

写widget.cpp

#include "widget.h"
#include "ui_widget.h"
#include <QTimer>
#include <QQmlContext>
widget::widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::widget)
{

    ui->setupUi(this);

    engine.rootContext()->setContextProperty("Widget",this);
    //将QML中的Widget变量指向为当前类.从而使QML和widget类连接起来

    engineObject = QQmlComponent(&engine, "qrc:/main.qml").create();        //创建qml并获取运行中的qml对象
}

widget::~widget()
{
    delete ui;
}

void widget::invokeFunc(QVariant data1,QVariant data2)
{
    ui->plainTextEdit->setPlainText(data1.toString());

}

void widget::on_pushButton_clicked()
{
     QVariant depatment= "";
     QVariant start= ui->start->text();
     QVariant end = ui->end->text();    //"结束日期"

     QMetaObject::invokeMethod(engineObject, "getWrenchTools",Q_ARG(QVariant, depatment)\
                             ,Q_ARG(QVariant, start),Q_ARG(QVariant, end));

}

• engine.rootContext()->setContextProperty("Widget",this)的作用:

将QML中的Widget变量指向为当前类.从而使QML和widget类连接起来, 然后main.qml如果post成功则调用当前类的invokeFunc(QVariant data1,QVariant data2)方法,从而实现数据返回.

• 当按下同步按钮时,则调用on_pushButton_clicked():

由于engineObject指向运行中的qml对象,然后我们通过invokeMethod()就可以方便的请求调用qml对象中的getWrenchTools()函数.从而实现post请求

点击同步后,效果如下所示(然后可以参考50.Qt-QJsonDocument读写json来提取数据):

 注意-如果出现QQmlComponent: Component is not ready字段,说明qml和js所在路径不在界面文件夹里

创建文件的时候,就需要将文件都放在界面目录中,才行: