Qt Documentation

Contents

ScrollBar QML Type

Vertical or horizontal interactive scroll bar. More...

Import Statement: import QtQuick.Controls 2.14
Since: Qt 5.7
Inherits:

Control

Properties

Attached Properties

Methods

Detailed Description

ScrollBar is an interactive bar that can be used to scroll to a specific position. A scroll bar can be either vertical or horizontal, and can be attached to any Flickable, such as ListView and GridView.

Flickable {
    // ...
    ScrollBar.vertical: ScrollBar { }
}

Attaching ScrollBar to a Flickable

When ScrollBar is attached vertically or horizontally to a Flickable, its geometry and the following properties are automatically set and updated as appropriate:

An attached ScrollBar re-parents itself to the target Flickable. A vertically attached ScrollBar resizes itself to the height of the Flickable, and positions itself to either side of it based on the layout direction. A horizontally attached ScrollBar resizes itself to the width of the Flickable, and positions itself to the bottom. The automatic geometry management can be disabled by specifying another parent for the attached ScrollBar. This can be useful, for example, if the ScrollBar should be placed outside a clipping Flickable. This is demonstrated by the following example:

Flickable {
    id: flickable
    clip: true
    // ...
    ScrollBar.vertical: ScrollBar {
        parent: flickable.parent
        anchors.top: flickable.top
        anchors.left: flickable.right
        anchors.bottom: flickable.bottom
    }
}

Notice that ScrollBar does not filter key events of the Flickable it is attached to. The following example illustrates how to implement scrolling with up and down keys:

Flickable {
    focus: true

    Keys.onUpPressed: scrollBar.decrease()
    Keys.onDownPressed: scrollBar.increase()

    ScrollBar.vertical: ScrollBar { id: scrollBar }
}

Binding the Active State of Horizontal and Vertical Scroll Bars

Horizontal and vertical scroll bars do not share the active state with each other by default. In order to keep both bars visible whilst scrolling to either direction, establish a two-way binding between the active states as presented by the following example:

Flickable {
    anchors.fill: parent

    contentWidth: parent.width * 2
    contentHeight: parent.height * 2

    ScrollBar.horizontal: ScrollBar { id: hbar; active: vbar.active }
    ScrollBar.vertical: ScrollBar { id: vbar; active: hbar.active }
}

Non-attached Scroll Bars

It is possible to create an instance of ScrollBar without using the attached property API. This is useful when the behavior of the attached scroll bar is not sufficient or a Flickable is not in use. In the following example, horizontal and vertical scroll bars are used to scroll over the text without using Flickable:

Rectangle {
    id: frame
    clip: true
    width: 160
    height: 160
    border.color: "black"
    anchors.centerIn: parent

    Text {
        id: content
        text: "ABC"
        font.pixelSize: 160
        x: -hbar.position * width
        y: -vbar.position * height
    }

    ScrollBar {
        id: vbar
        hoverEnabled: true
        active: hovered || pressed
        orientation: Qt.Vertical
        size: frame.height / content.height
        anchors.top: parent.top
        anchors.right: parent.right
        anchors.bottom: parent.bottom
    }

    ScrollBar {
        id: hbar
        hoverEnabled: true
        active: hovered || pressed
        orientation: Qt.Horizontal
        size: frame.width / content.width
        anchors.left: parent.left
        anchors.right: parent.right
        anchors.bottom: parent.bottom
    }
}

When using a non-attached ScrollBar, the following must be done manually:

  • Layout the scroll bar (with the x and y or anchors property, for example).
  • Set the size and position properties to determine the size and position of the scroll bar in relation to the scrolled item.
  • Set the active property to determine when the scroll bar will be visible.

See also ScrollIndicator, Customizing ScrollBar, and Indicator Controls.

Property Documentation

active : bool

This property holds whether the scroll bar is active, i.e. when it's pressed or the attached Flickable is moving.

It is possible to keep both horizontal and vertical bars visible while scrolling in either direction.

This property is automatically set when the scroll bar is attached to a flickable.


[read-only] horizontal : bool

This property holds whether the scroll bar is horizontal.

This property was introduced in QtQuick.Controls 2.3 (Qt 5.10).

See also orientation.


interactive : bool

This property holds whether the scroll bar is interactive. The default value is true.

A non-interactive scroll bar is visually and behaviorally similar to ScrollIndicator. This property is useful for switching between typical mouse- and touch-orientated UIs with interactive and non-interactive scroll bars, respectively.

This property was introduced in QtQuick.Controls 2.2 (Qt 5.9).


minimumSize : real

This property holds the minimum size of the scroll bar, scaled to 0.0 - 1.0.

This property was introduced in QtQuick.Controls 2.4 (Qt 5.11).

See also size, visualSize, and visualPosition.


orientation : enumeration

This property holds the orientation of the scroll bar.

Possible values:

ConstantDescription
Qt.HorizontalHorizontal
Qt.VerticalVertical (default)

This property is automatically set when the scroll bar is attached to a flickable.

See also horizontal and vertical.


policy : enumeration

This property holds the policy of the scroll bar. The default policy is ScrollBar.AsNeeded.

Possible values:

ConstantDescription
ScrollBar.AsNeededThe scroll bar is only shown when the content is too large to fit.
ScrollBar.AlwaysOffThe scroll bar is never shown.
ScrollBar.AlwaysOnThe scroll bar is always shown.

The following example keeps the vertical scroll bar always visible:

Flickable {
    contentHeight: 2000
    ScrollBar.vertical: ScrollBar {
        policy: ScrollBar.AlwaysOn
    }
}

This property was introduced in QtQuick.Controls 2.2 (Qt 5.9).


position : real

This property holds the position of the scroll bar, scaled to 0.0 - 1.0.

This property is automatically set when the scroll bar is attached to a flickable.

See also Flickable::visibleArea and visualPosition.


pressed : bool

This property holds whether the scroll bar is pressed.


size : real

This property holds the size of the scroll bar, scaled to 0.0 - 1.0.

This property is automatically set when the scroll bar is attached to a flickable.

See also Flickable::visibleArea, minimumSize, and visualSize.


snapMode : enumeration

This property holds the snap mode.

Possible values:

ConstantDescription
ScrollBar.NoSnapThe scrollbar does not snap (default).
ScrollBar.SnapAlwaysThe scrollbar snaps while dragged.
ScrollBar.SnapOnReleaseThe scrollbar does not snap while being dragged, but only after released.

In the following table, the various modes are illustrated with animations. The movement and the stepSize (0.25) are identical in each animation.
ValueExample
ScrollBar.NoSnap

ScrollBar.SnapAlways

ScrollBar.SnapOnRelease

This property was introduced in QtQuick.Controls 2.2 (Qt 5.9).

See also stepSize.


stepSize : real

This property holds the step size. The default value is 0.0.

See also snapMode, increase(), and decrease().


[read-only] vertical : bool

This property holds whether the scroll bar is vertical.

This property was introduced in QtQuick.Controls 2.3 (Qt 5.10).

See also orientation.


visualPosition : real

This property holds the effective visual position of the scroll bar, which may be limited by the minimum size.

This property was introduced in QtQuick.Controls 2.4 (Qt 5.11).

See also position and minimumSize.


visualSize : real

This property holds the effective visual size of the scroll bar, which may be limited by the minimum size.

This property was introduced in QtQuick.Controls 2.4 (Qt 5.11).

See also size and minimumSize.


Attached Property Documentation

ScrollBar.horizontal : ScrollBar

This property attaches a horizontal scroll bar to a Flickable.

Flickable {
    contentWidth: 2000
    ScrollBar.horizontal: ScrollBar { }
}

See also Attaching ScrollBar to a Flickable.


ScrollBar.vertical : ScrollBar

This property attaches a vertical scroll bar to a Flickable.

Flickable {
    contentHeight: 2000
    ScrollBar.vertical: ScrollBar { }
}

See also Attaching ScrollBar to a Flickable.


Method Documentation

void decrease()

Decreases the position by stepSize or 0.1 if stepSize is 0.0.

See also stepSize.


void increase()

Increases the position by stepSize or 0.1 if stepSize is 0.0.

See also stepSize.


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