QML animation - moving the application window - qt

Question

I want to create an animation to move (or resize) my application Window built using QML.
I have the following code (most of it created by default when we create a QT quick Controls application:
main.cpp
#include <QApplication>
#include <QQmlApplicationEngine>
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QQmlApplicationEngine engine;
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
return app.exec();
}
MainForm.ui.qml
import QtQuick 2.6
import QtQuick.Controls 1.5
import QtQuick.Layouts 1.3
Item {
width: 640
height: 480
property alias button1: button1
property alias button2: button2
RowLayout {
anchors.centerIn: parent
Button {
id: button1
text: qsTr("Press Me 1")
}
Button {
id: button2
text: qsTr("Press Me 2")
}
}
}
main.qml
import QtQuick 2.6
import QtQuick.Controls 1.5
import QtQuick.Dialogs 1.2
ApplicationWindow {
id: mainWindow
visible: true
width: 640
height: 480
title: qsTr("Hello World")
flags: Qt.FramelessWindowHint | Qt.WindowStaysOnTopHint
menuBar: MenuBar {
Menu {
title: qsTr("File")
MenuItem {
text: qsTr("&Open")
onTriggered: console.log("Open action triggered");
}
MenuItem {
text: qsTr("Exit")
onTriggered: Qt.quit();
}
}
}
MainForm {
anchors.fill: parent
button1.onClicked: Qt.quit();
button2.onClicked: state = "other";
}
transitions: [
Transition {
from: "*"
to: "other"
NumberAnimation { properties: "x,y"; easing.type: Easing.InOutQuad; duration: 2000 }
}
]
states: [
State {
name: "other"
PropertyChanges {
target: mainWindow
x: x + 200
}
}
]
MessageDialog {
id: messageDialog
function show(caption) {
messageDialog.text = caption;
messageDialog.open();
}
}
}
With this code, I was simply trying to move my window 200 pixels to the right. When I try to run it, I get qrc:/main.qml:42 Cannot assign to non-existent property "states". I believe that is weird, because when I start typing "states" and choose to auto-complete, it builds to me the whole structure, so I thought it should exist...
I'm new to QML, and I'm not fully familiar with the several options of animations that exists. This one I've tried based on the example that comes with QT creator (animation.pro - code from transitions).
I believe it should be quite simple, right? Could you help me with this?

Answer 1

Qt Creator has a feature where you can insert code snippets using certain keywords. You can see which snippets are available by going to Tools > Options > Text Editor > Snippets.
Snippets will show up as red in the auto completion popup, and regular properties (or types, as is the case below) will show up as green:
So, ApplicationWindow doesn't have a states property. If you're ever in doubt, go to the documentation for the type you're interested in (e.g. http://doc.qt.io/qt-5/qml-qtquick-controls-applicationwindow.html) and click on the link that says "List of all members, including inherited members". This will show you all properties, functions, etc. belonging
to that type.
If you want to animate the window's position, you can use a NumberAnimation without using states:
import QtQuick 2.6
import QtQuick.Window 2.2
import QtQuick.Controls 1.5
ApplicationWindow {
id: window
width: 400
height: 400
visible: true
NumberAnimation {
id: xyAnimation
target: window
properties: "x,y"
easing.type: Easing.InOutQuad
duration: 2000
to: 500
}
Button {
text: "Start"
onClicked: xyAnimation.start()
}
}

Answer 2

state is a property in Item, however ApplicationWindow is not an Item. To add state/transition to an non-Item type, use StateGroup:
ApplicationWindow {
id: mainWindow
//your code...
MainForm {
button2.onClicked: { myWindowStates.state = "other";}
}
StateGroup {
id: myWindowStates
transitions: [
Transition {
from: "*"; to: "other"
NumberAnimation {
properties: "x,y"; easing.type: Easing.Linear;
duration: 2000
}
}
]
states: [
State {
name: "other"
PropertyChanges {
target: mainWindow
x: mainWindow.x + 200
explicit: true //Remember to set this
}
}
]
}
}
Remember to set PropertyChange.explict to true, otherwise the state behavior is wrong and your window will disappear after the transition finished.