How to animate Qt speedguage

[A Former User]

I am new to Qt. I am a hardware guy. I wanted to use Qt for displaying the benchmark results of a code (execution time) for a demo. I thought it would be more presentable if I displayed it in a visually appealing manner.

I came across a example implementation of a Speed gauge in Qt at this link: https://github.com/Berrima/Qt-custom-gauge-widget/tree/master/examples/SpeedGauge

I want to display a number (say 900) on the speed gauge and this can be done by setting a value of the needle. But I want the needle to gradually increase and stop at 900.
After some research I think QAnimation has to be used. But I cant seem to understand how to use it.

Can someone please give me some idea how to proceed on this as I am very new to this and I have limited time.

Any help is greatly appreciated. Thanks in advance.

[JKSH]

Hi @nidx, and welcome to the Qt Dev Net!

For the gauge that you're using, the fastest way is to:

1. Modify QcNeedleItem to make "currentValue" a QObject property (see http://doc.qt.io/qt-5/properties.html ), and then
2. Use QPropertyAnimation to animate "currentValue" (see http://doc.qt.io/qt-5/animation-overview.html )

[A Former User]

@JKSH Thank you very much. Will try it and let you know.

[A Former User]

Hi @JKSH.
I tried what you suggested I modified the QcNeedleItem to make "currentValue" as a QObject property as follows:

class QCGAUGE_DECL QcNeedleItem : public QcScaleItem
{
Q_OBJECT
Q_PROPERTY(float currentValue MEMBER mCurrentValue READ currentValue WRITE setCurrentValue)
public:
explicit QcNeedleItem(QObject parent = 0);
void draw(QPainter);
void setCurrentValue(float value);
float currentValue();
void setColor(const QColor & color);
float mCurrentValue;
QColor color();
void setLabel(QcLabelItem*);
QcLabelItem * label();

enum NeedleType{DiamonNeedle,TriangleNeedle,FeatherNeedle,AttitudeMeterNeedle,CompassNeedle};//#

void setNeedle(QcNeedleItem::NeedleType needleType);

private:
QPolygonF mNeedlePoly;
QColor mColor;
void createDiamonNeedle(float r);
void createTriangleNeedle(float r);
void createFeatherNeedle(float r);
void createAttitudeNeedle(float r);
void createCompassNeedle(float r);
NeedleType mNeedleType;
QcLabelItem *mLabel;
};

And Also in the mainwindow.cpp, I tried to animate the currentValue as follows:

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "../../source/qcgaugewidget.h"
#include <QPropertyAnimation>
#include <QTimer>
#include <sys/time.h>
#include <unistd.h>

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);

mSpeedGauge = new QcGaugeWidget;
mSpeedGauge->addBackground(99);
QcBackgroundItem *bkg1 = mSpeedGauge->addBackground(92);
bkg1->clearrColors();
bkg1->addColor(0.1,Qt::black);
bkg1->addColor(1.0,Qt::white);

QcBackgroundItem *bkg2 = mSpeedGauge->addBackground(88);
bkg2->clearrColors();
bkg2->addColor(0.1,Qt::gray);
bkg2->addColor(1.0,Qt::darkGray);

mSpeedGauge->addArc(55);
mSpeedGauge->addDegrees(65)->setValueRange(0,100);
mSpeedGauge->addColorBand(50);

mSpeedGauge->addValues(80)->setValueRange(0,100);

mSpeedGauge->addLabel(70)->setText("GFLOPS");
QcLabelItem *lab = mSpeedGauge->addLabel(40);
lab->setText("0");
mSpeedNeedle = mSpeedGauge->addNeedle(60);
mSpeedNeedle->setLabel(lab);
mSpeedNeedle->setColor(Qt::white);
mSpeedNeedle->setValueRange(0,80);
mSpeedGauge->addBackground(7);
mSpeedGauge->addGlass(88);
ui->verticalLayout->addWidget(mSpeedGauge);

QcNeedleItem *currentValue=new QcNeedleItem(this);
currentValue->setCurrentValue(0);


QPropertyAnimation animation(currentValue, "geometry");
animation.setDuration(5000);
animation.setStartValue(0);
animation.setEndValue(50);

animation.start();

}

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

void MainWindow::on_horizontalSlider_valueChanged(int value)
{

mSpeedNeedle->setCurrentValue(value);

}

But I get the following warning and the currentValue is not animated:
QPropertyAnimation: you're trying to animate a non-existing property geometry of your QObject.

Do you know what I might be doing wrong?

[JKSH]

@nidx said:

Do you know what I might be doing wrong?

You called your property "currentValue", not "geometry". Which name do you want to use?

[yeckel]

@nidx said:
Constructor for QPropertyAnimation is:
QPropertyAnimation::QPropertyAnimation(QObject * target, const QByteArray & propertyName, QObject * parent = 0)

thus you have to write rather:
QPropertyAnimation animation(currentValue, "currentValue");