Qt Reference Documentation

QML Tutorial 1 - Basic Types

This first program is a very simple "Hello world" example that introduces some basic QML concepts. The picture below is a screenshot of this program.

Here is the QML code for the application:

 import Qt 4.7

 Rectangle {
     id: page
     width: 500; height: 200
     color: "lightgray"

     Text {
         id: helloText
         text: "Hello world!"
         y: 30
         anchors.horizontalCenter: page.horizontalCenter
         font.pointSize: 24; font.bold: true
     }
 }

Walkthrough

Import

First, we need to import the types that we need for this example. Most QML files will import the built-in QML types (like Rectangle, Image, ...) that come with Qt, using:

 import Qt 4.7

Rectangle element

 Rectangle {
     id: page
     width: 500; height: 200
     color: "lightgray"

We declare a root element of type Rectangle. It is one of the basic building blocks you can use to create an application in QML. We give it an id to be able to refer to it later. In this case, we call it "page". We also set the width, height and color properties. The Rectangle element contains many other properties (such as x and y), but these are left at their default values.

Text element

     Text {
         id: helloText
         text: "Hello world!"
         y: 30
         anchors.horizontalCenter: page.horizontalCenter
         font.pointSize: 24; font.bold: true
     }

We add a Text element as a child of the root Rectangle element that displays the text 'Hello world!'.

The y property is used to position the text vertically at 30 pixels from the top of its parent.

The anchors.horizontalCenter property refers to the horizontal center of an element. In this case, we specify that our text element should be horizontally centered in the page element (see Anchor-based Layout).

The font.pointSize and font.bold properties are related to fonts and use the dot notation.

Viewing the example

To view what you have created, run the QML Viewer tool (located in the bin directory) with your filename as the first argument. For example, to run the provided completed Tutorial 1 example from the install location, you would type:

 bin/qmlviewer $QTDIR/examples/declarative/tutorials/helloworld/tutorial1.qml

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