A bug about Keyboard Focus in Qt Quick in QT 5.10 document?

1
votes

I am reading the Qt doc to learn the Keyboard Focus in Qt Quick! I run the code which from the document. However, the result is different form the document! The codes are as follows.

main.qml

//Window code that imports MyWidget
Rectangle {
id: window
color: "white"; width: 240; height: 150

Column {
    anchors.centerIn: parent; spacing: 15

    MyWidget {
        focus: true             //set this MyWidget to receive the focus
        color: "lightblue"
    }
    MyWidget {
        color: "palegreen"
    }
}

MyWidget.qml

Rectangle {
  id: widget
  color: "lightsteelblue"; width: 175; height: 25; radius: 10; antialiasing: 
  true
  Text { id: label; anchors.centerIn: parent}
  focus: true
  Keys.onPressed: {
      if (event.key == Qt.Key_A)
          label.text = 'Key A was pressed'
      else if (event.key == Qt.Key_B)
          label.text = 'Key B was pressed'
      else if (event.key == Qt.Key_C)
          label.text = 'Key C was pressed'
   }
}

The pic1 is the result form doc. And the pic2 is the result of my running which i just copy the code from doc and run it.

pic1 pic1

pic2 pic2

Is it a bug? Why the result are different?

The doc said:

We want the first MyWidget object to have the focus, so we set its focus property to true. However, by running the code, we can confirm that the second widget receives the focus.

Looking at both MyWidget and window code, the problem is evident - there are three types that set the focus property to true. The two MyWidgets set the focus to true and the window component also sets the focus. Ultimately, only one type can have keyboard focus, and the system has to decide which type receives the focus. When the second MyWidget is created, it receives the focus because it is the last type to set its focus property to true.

My question:

1.Why the result are different?In my result the first widget receives the focus.

2.Also, what is the meaning of"because it is the last type to set its focus property to true"in doc?

The doc you can get from here! Qt doc

3
c++qtqtquick2qt-quick
Someones can help? – Ryou

3 Answers

0
votes

When I run the code I get the same result as you, but it does not matter. The point here is to understand that without FocusScope you have no control on which object receives the focus from the system (you have no guarantee in the order of creation of QML objects).

Did you try to set focus: true on the second MyWidget instead? If you try, the keyboard events will still be received by the first widget, except if you use a FocusScope.

Note that you can also remove focus: true from MyWidget.qml and you won't even need to manually add a FocusScope (it will automatically be managed by the application window).

0
votes

try run with the following modification:

MyWidget {                  //the focus is here
    color: "palegreen"
}
MyWidget {
    focus: true             //set this MyWidget to receive the focus
    color: "lightblue"
}
MyWidget {
    color: "palegreen"
}
-1
votes

I tested many times. The result is the same. Maybe the docs are outdated!