Saturday, December 11, 2010

[Qt] Push-ups Counter: Step1-Functionality

I made the first version of my Push-ups counter using Qt. It is based on using the accelerometer to sense the movement of the mobile. In this version:
- It has a settings screen with only one option till now: Mute Sound.
- The next screen counts the push-ups depending on some internally-set variables (the positions of up/down)
- It makes a beep when I reach the up/down position, so I know if I'm up/down enough.
= I noticed that if my arm shakes, it may count extra points.(to be fixed)

The main important points in the application are how to read the device's position and how to count.
To read the position, I read the "x" value of the accelerometer:
I use two classes: QSensor, QSensorReading

QSensor *sensor = new QSensor("QAccelerometer");
QSensorReading *reading = sensor->reading();
int value = abs(reading->property("x").value<qreal>()/1);

Some notes:
- The abs() method is because the value can be +ve or -ve depending on which arm I use, so I just take the absolute value.
- The value<qreal>()/1 is a simple way of moving any noise. If I get the value as int, it will be in a big range (I can't remember it right now), and it may be useful in sensitive applications but not in this case. The range I get is 0-9. And the division by 1 is to neglect the fractions.

I added two flags to detect if the next calculation to for going up or down. An a timer to calculate the value of the accelerometer every period of time. I know that the QSensor class has a signal of readingChanged(), but it is very rapid and will exhaust the processor.

void CounterWindow::readSensorValue()
    int value = abs(reading->property("x").value<qreal>()/1);

        if(value <= upValue)
            if(!muted) QApplication::beep();
            nextUp = false;
            nextDown = true;
    else if(nextDown)
        if(value >= downValue)
            if(!muted) QApplication::beep();
            nextUp = true;
            nextDown = false;

I also had to add some Symbian code to disable the change of orientation when the mobile rotates and force the Portrait orientation.

symbian {
    LIBS += -lcone -leikcore -lavkon

// Needed Symbian specific headers
#include <eikenv.h>
#include <eikappui.h>
#include <aknenv.h>
#include <aknappui.h>

and add this code before calling the window
StartingWindow w;
#if defined(Q_OS_SYMBIAN)
    CAknAppUi* appUi = dynamic_cast<CAknAppUi*>(CEikonEnv::Static()->AppUi());
            QT_TRAP_THROWING(appUi ->SetOrientationL(CAknAppUi::EAppUiOrientationPortrait));

So... the next step is for the Look&Feel and fixing any bug that may appear.

Download v1.0

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