Qt 5.9 | Qt Quick Controls 2 | QML Types | ScrollBar QML Type

Qt 5.9.2 Reference Documentation

# ScrollBar QML Type

Vertical or horizontal interactive scroll bar. More...

Import Statement: | import QtQuick.Controls 2.2
Since: | Qt 5.7
Inherits: | Control

- List of all members, including inherited members

## Properties

- active : bool
- interactive : bool
- orientation : enumeration
- policy : enumeration
- position : real
- pressed : bool
- size : real
- snapMode : enumeration
- stepSize : real

## Attached Properties

- horizontal : ScrollBar
- vertical : ScrollBar

## Methods

- void decrease()
- void increase()

## 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:

- orientation
- position
- size
- active

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 scoll 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 anchor properties, 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.

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

orientation : enumeration

This property holds the orientation of the scroll bar.

Possible values:

Constant | Description
--- | ---
`Qt.Horizontal` | Horizontal
`Qt.Vertical` | Vertical (default)

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

policy : enumeration

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

Possible values:

Constant | Description
--- | ---
`ScrollBar.AsNeeded` | The scroll bar is only shown when the content is too large to fit.
`ScrollBar.AlwaysOff` | The scroll bar is never shown.
`ScrollBar.AlwaysOn` | The 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 QML 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.

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.

snapMode : enumeration

This property holds the snap mode.

Possible values:

Constant | Description
--- | ---
`ScrollBar.NoSnap` | The scrollbar does not snap (default).
`ScrollBar.SnapAlways` | The scrollbar snaps while dragged.
`ScrollBar.SnapOnRelease` | The 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.

Value | Example
`ScrollBar.NoSnap` |
`ScrollBar.SnapAlways` |
`ScrollBar.SnapOnRelease` |

This QML 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().

## 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.