Why it doesnt emit ?

Montanaro

I m not able to understand why my code doents emit.

My task is: reading battery level and showing immagine with battery level.

So this i my code:

battery.ccp

Battery::Battery(QObject *parent) :
  QObject(parent),
    timer{ new QTimer(this) }
{

    qDebug()<<"class Battery";


    connect(timer, &QTimer::timeout, this, &Battery::checkBatteryLevel);

    timer->start(std::chrono::milliseconds(2000));
}







void Battery::checkBatteryLevel()
{     QFile batteryFile(BATTERY_FILE_NAME);

      if (batteryFile.open(QIODevice::ReadOnly | QIODevice::Text))
      {
          qDebug()<<"file open";
      }
      else
      {
          qDebug()<<"file not open";
          return;

      }


    if (QTextStream(&batteryFile).readAll().toInt() < 25)  {
        qDebug() << "first level battery";
        emit batteryLevel(1);
    }

    if (QTextStream(&batteryFile).readAll().toInt() > 25)  {
        qDebug()<< "second level battery";
        emit batteryLevel(2);
    }
}

main.qml

ApplicationWindow {
    id: applicationWindow
    visible: true
    width: 419
    height: 138
    color: "black"

    // the current date and time
    property date now: null


    
    
    property int index: 0
    property var slidesPath: [
   
        "qrc:/res/icons/low_batt.png",
        "qrc:/res/icons/med_batt.png",
        "qrc:/res/icons/med_high_battery.png",
         "qrc:/res/icons/icons/no_app_found.png"

    ]

   Image {
        id: ic
        width:  90
        y: 22
        fillMode: Image.PreserveAspectFit
        source: slidesPath[index]  //
        height: width
        anchors.left: parent.left
        anchors.leftMargin: 20
        anchors.verticalCenter: parent.verticalCenter

    }


     Text {
        y:   60
         text: new Date().toLocaleTimeString(Qt.LocaleDate)

         //  new Date().toLocaleDateString(Qt.locale("it_IT"))  //
        anchors.left: ic.right
        anchors.leftMargin:  1
        anchors.top: parent.top
        anchors.topMargin: 10
        anchors.verticalCenter: parent.verticalCenter
        font.bold: true
        font.pointSize: 14
        color: "white"
    }


     Text {
        y:   60
         text:  new Date().toLocaleDateString(Qt.locale("en_EN"))  //
        anchors.left: ic.right
        anchors.leftMargin: 1
        anchors.top: parent.top
        anchors.topMargin: 30
        anchors.verticalCenter: parent.verticalCenter
        font.bold: true
        font.pointSize: 14
        color: "white"
    }


     Text {
         id: txt
         text: "nome app variabile"
         height: 50
         font.capitalization: Font.AllUppercase
         color: "white"
         font.bold: true
         font.pointSize: 18 //36
         anchors.left: ic.right
         anchors.leftMargin: 1 //20
         anchors.topMargin: 70
         anchors.verticalCenter: parent.verticalCenter
         verticalAlignment: Text.AlignVCenter
     }


  Text {
           text: qsTr(".")
           anchors.centerIn: parent
           focus: true

  Keys.onPressed: {
                  if (event.key === Qt.Key_Up) {

                          if (index < slidesPath.length - 1)
                              index++;


                          process.start("c:\\windows\\notepad.exe");
                          process.waitForFinished();

                              index = 0;


                  } else if (event.key === Qt.Key_Down) {

                      if (index > 0)
                          index--;

                      else
                          index = 3;
               }
      }


  }


  Battery {
      id: batteryLevel

  //  swipeView.currentIndex--;
      onValueChanged: {
          console.log("battery ");
                  switch (percent)
                  {case 1:
                       slidesPath[2];  //  source: "qrc:/res/icons/low_batt.png"
                        console.log("case 1 ");
                    break;

                  case 2:
                     applicationWindow.index=3;
                      console.log("case 2 ");
                    //  source: "qrc:/res/icons/med_batt.png"
                  break; }
  }

My logs are:

class Battery
file open
first level battery
file open
first level battery
.........

fcarney

You are looking at onValueChanged. Shouldn't you be looking at onBatteryLevelChanged? You are emitting batteryLevel(int).

Edit: Or is it onBatteryLevel? Also, there is slot for QTimer::start that takes int as well as milliseconds.

SGaist

Hi,

Beside the good suggestion of @fcarney, you might be in the unlucky case of the battery value being 25 thus nothing will be emitted.

On a side note, it would make your code way more clean, readable and error proof to read and convert the value once (doing a conversion check would be good as well) and then apply your logic. You currently create two streams and read the file twice which is a bit inefficient and not clean from a maintenance point of view.

Montanaro

@fcarney

oh yes, with "onBatteryLevel" it works and I can use the switch.
Mmm... now I have to know because I dont see slide :D

yes I used timer of 2 seconds.
I want to check battery level

Montanaro

@SGaist
I dont understand what you suggest.
can you write example please ?

@fcarney : ```
applicationWindow.index= number;
` is correct to show slide :D

jsulm

@Montanaro said in Why it doesnt emit ?:

I dont understand what you suggest

In your code you clearly read the content of the file two times:

if (QTextStream(&batteryFile).readAll().toInt() < 25)  {
    qDebug() << "first level battery";
    emit batteryLevel(1);
}
if (QTextStream(&batteryFile).readAll().toInt() > 25)  {
    qDebug()<< "second level battery";
    emit batteryLevel(2);
}

It is enough and also faster to do it once. And toInt() has a bool parameter to check whther the content of the string could be converted to an int (if the string does not contain valid integer number toInt() will fail):

bool ok{false};
int value = QTextStream(&batteryFile).readAll().toInt(&ok);
if (!ok) {
    // Handle the error here
}
if (value < 25)  {
    qDebug() << "first level battery";
    emit batteryLevel(1);
}
if (value > 25)  {
    qDebug()<< "second level battery";
    emit batteryLevel(2);
}

Montanaro

@jsulm

oh thanks. you are right :)

well... all my questions are solved ! thanks to all !

I tryed to change "unsolved tag" into "solved tag but" but I m not able :/

J.Hilk

@Montanaro said in Why it doesnt emit ?:

I tryed to change "unsolved tag" into "solved tag but" but I m not able :/

bottom right, topic tools -> mark as solved