On Samsung devices, like tablets and smartphones, it is impossible to receive keys from the virtual keyboard, by using Keys.onPressed or Keys.onRelease, except for DEL and ENTER keys. So the following simple code doesn't work:

    import QtQuick 2.2
    import QtQuick.Window 2.1
    import QtQuick.Controls 1.2
     
    ApplicationWindow {
    visible: true
    width: 640
    height: 400
     
    toolBar: ToolBar {
        Row {
            anchors.fill: parent
            ToolButton {
                text: "Exit"
                onClicked: Qt.quit();
            }
        }
    }
     
    TextInput {
        width: 200
        height: 40
        focus: true
     
        Keys.onPressed: {
            console.log("Key="+event.key+" "+event.text);
        }
        Keys.onReleased: {
            console.log("Key="+event.key+" "+event.text);
        }
    }
    }

Currently, Qt returns an error when a key is pressed on virtual keyboard:

W/Qt (26304): kernel\qmetaobject.cpp:1458 (static bool QMetaObject::invokeMethod(QObject*, const char*, Qt::ConnectionType, QGenericReturnArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument)): QMetaObject::invokeMethod: No such method QQuickTextInput::inputMethodQuery(Qt::InputMethodQuery,QVariant)

The suggestion is to implement this missing functionality (may be absent also in iOS)