[Solved] Sliding Bar Graph
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Yes this is possible. Some tags to search for on QtDevNet are things like "qml c++ integration".
The basic principal is that you create a C++ class that inherits QObject and in this class you declare some properties using Q_DECLARE_PROPERTY macro. These properties represent the quantities that you wish to display in your QML gui. You then expose your C++ object(s) to the QDeclarativeConext object using the setContextProperty() function.
In you QML gui you can then bind properties of your QML items to the properties of your C++ object(s).
It is up to you how to factor your C++ object(s) and their properties to map onto your data.
This kind of design leads to a nice separation of concerns. You will have a component that retrieves the data from your existing C application somehow and populates the properties of your C++ QObject subclasses. Then you have your GUI in QML which is only dependent upon the names and types of object and properties exposed to it form the C++ side. So you can very easily swap out the GUI for a new one without touching the backend code if needed.
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Hi,
I tried your progress bar graph illustration it was working fine, when I used it with a single value change from the C++ program.
I am trying to change the graph value with the values from the external "C" program using Qprocess. I am not sure on how to proceed with the program structure. Can you please suggest me. Should the QProcess be a part of some class along with the QML?.
Thanks for your assistance.
Balaji
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ZapB,
I was able to connect the QML and was able to connect to the output of the C program(the program just outputs from 1 to 100) using QProcess. However the value from the standard output seems to be a stream and the toInt function does not recognize it and returns a value of '0' and the Graph displays with no fill.
Thanks a lot for providing your valuable assistance.
BsBalaThis is the coding for the Qprocess.
@#include <QApplication>
#include <QDeclarativeView>
#include <QDeclarativeContext>
#include <QDeclarativeProperty>
#include <QGraphicsObject>
#include <QDebug>
#include<QObject>
#include<QProcess>#include "processconnector.h"
#include "slidinggraph.h"ProcessConnector::ProcessConnector(QObject *parent){
process = new QProcess(this);
process->setReadChannel(QProcess::StandardOutput);
connect(process, SIGNAL(readyReadStandardOutput()),this, SLOT(disp()));
process->start("./op");}
void ProcessConnector::disp()
{
while( 1 ){
QString t = process->readLine();
if( t.isEmpty() ) break;
qDebug() << "got output" << t.toInt();
emit valueChanged(t.toInt());}
}
@This is the coding for the QML object.
@#include <QApplication>
#include <QDeclarativeView>
#include <QDeclarativeContext>
#include <QDeclarativeProperty>
#include <QGraphicsObject>
#include <QDebug>
#include<QObject>
#include<QProcess>
#include<slidinggraph.h>SlidingGraph::SlidingGraph(QObject *parent){
view.setSource(QUrl::fromLocalFile("qml/QMLconnector/main.qml"));
QObject object = view.rootObject();
progressbar = object->findChild<QObject>("bar");
view.show();
}void SlidingGraph::setvalue(int value){
if(progressbar)
progressbar->setProperty("value",value);}
@This is the main.cpp
@#include <QtGui/QApplication>
#include "qmlapplicationviewer.h"
#include "processconnector.h"
#include "slidinggraph.h"
#include <QObject>int main(int argc, char *argv[])
{
QApplication app(argc, argv);ProcessConnector *Pc = new ProcessConnector(); SlidingGraph *sl = new SlidingGraph(); QObject::connect(Pc,SIGNAL(valueChanged(int)),sl,SLOT(setvalue(int))); sl->view.show(); return app.exec();}
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Hi ZapB,
Nice to hear from you. Actually I had my friend code the C part which had some mistakes. He corrected it . I had good sliding graph. Thanks for your help.I got a good idea for working with QML. I have some other questions about QML multiple screens and how to make underlying Qt C++ layer to handle it. I will post it in a new thread. Please help me out if you find some time.
I appreciate all your help, guidance and time you have taken to reply my questions.
Balaji