QML 从入门到放弃 第二卷

第二卷如何更快速的放弃，注重的是C++和QML的交互

<1>记事本。。

(1) 先测试下不在QML创建C++对象，仅仅在main.cpp添加一个属性函数供调用.

TextStreamLoader.h

#ifndef TEXTSTREAMLOADER_H
#define TEXTSTREAMLOADER_H

#include <QObject>
#include <QTextStream>
#include <QDebug>
class TextStreamLoader : public QObject
{
    Q_OBJECT
public:
    explicit TextStreamLoader(QObject *parent = 0);

signals:
    void signal_readFile(QString file);
    void signal_error(QString errorMsg);
public slots:
    void slot_readFile(QString file);
    void slot_saveFile(QString file,QString buffer);
    void slot_test(){qDebug() << "test C++";}
};

#endif // TEXTSTREAMLOADER_H

TextStreamLoader.cpp

#include "TextStreamLoader.h"
#include <QFile>
TextStreamLoader::TextStreamLoader(QObject *parent) : QObject(parent)
{
    qDebug() << "Construct the TextStreamLoader";
}

void TextStreamLoader::slot_readFile(QString file)
{
    QFile rfile(file);
    if(!rfile.open(QIODevice::ReadOnly))
    {
        QString errorMsg = "Could not open " + file + "\n";
        emit signal_error(errorMsg);
        return ;
    }

    QTextStream in(&rfile);
    QString data = in.readAll();
    emit signal_readFile(data);

    rfile.close();

}

void TextStreamLoader::slot_saveFile(QString file, QString buffer)
{
    QFile wfile(file);
    if(!wfile.open(QFile::WriteOnly))
    {
        QString errorMsg = "Could not open " + file + "\n";
        emit signal_error(errorMsg);
        return ;
    }

    QTextStream out(&wfile);
    out >> buffer;
    wfile.close();

}

main.cpp

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>
#include "TextStreamLoader.h"
int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);

    QQmlApplicationEngine engine;
    QQmlContext *context = engine.rootContext();

    // 注意对象是在C++里构建
    TextStreamLoader stream_01;
    context->setContextProperty("stream_01",&stream_01);
    // 构建完C++对象

    // 加载我们的QML界面，只能调用槽函数
    qDebug() << "load the main.qml";
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

    qDebug() <<engine.rootObjects()[0]->objectName();  // this will be debug "Houdini"

    return app.exec();
}

main.qml 用最简单的测试下我们的TextStreamLoader 里面的 "test()槽函数",一定要是槽函数才能被调用

import QtQuick 2.6
import QtQuick.Window 2.2

Window
{
    objectName: "Houdini"
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")

    MouseArea {
        anchors.fill: parent
        onClicked: stream_01.slot_test(); // 并没有构建对象，因为在main.cpp构建的

    }

}