- Qt 6.8
- Qt Quick Controls
- QML Types
- Tumbler
- Qt 6.8.3 Reference Documentation

# Tumbler QML Type

Spinnable wheel of items that can be selected. More...

Import Statement: | `import QtQuick.Controls`
Inherits: | Control

- List of all members, including inherited members

## Properties

- count : int
- currentIndex : int
- currentItem : Item
- delegate : Component
- model : variant
- moving : bool `(since QtQuick.Controls 2.2 (Qt 5.9))`
- visibleItemCount : int
- wrap : bool `(since QtQuick.Controls 2.1 (Qt 5.8))`

## Attached Properties

- displacement : real
- tumbler : Tumbler

## Methods

- void positionViewAtIndex(int index, PositionMode mode) `(since QtQuick.Controls 2.5 (Qt 5.12))`

## Detailed Description

     Tumbler {
         model: 5
         // ...
     }

Tumbler allows the user to select an option from a spinnable "wheel" of items. It is useful for when there are too many options to use, for example, a RadioButton, and too few options to require the use of an editable SpinBox. It is convenient in that it requires no keyboard usage and wraps around at each end when there are a large number of items.

The API is similar to that of views like ListView and PathView; a model and delegate can be set, and the count and currentItem properties provide read-only access to information about the view. To position the view at a certain index, use positionViewAtIndex().

Unlike views like PathView and ListView, however, there is always a current item (when the model isn't empty). This means that when count is equal to `0`, currentIndex will be `-1`. In all other cases, it will be greater than or equal to `0`.

By default, Tumbler wraps when it reaches the top and bottom, as long as there are more items in the model than there are visible items; that is, when count is greater than visibleItemCount:

     import QtQuick
     import QtQuick.Window
     import QtQuick.Controls

     Rectangle {
         width: frame.implicitWidth + 10
         height: frame.implicitHeight + 10

         function formatText(count, modelData) {
             var data = count === 12 ? modelData + 1 : modelData;
             return data.toString().length < 2 ? "0" + data : data;
         }

         FontMetrics {
             id: fontMetrics
         }

         Component {
             id: delegateComponent

             Label {
                 text: formatText(Tumbler.tumbler.count, modelData)
                 opacity: 1.0 - Math.abs(Tumbler.displacement) / (Tumbler.tumbler.visibleItemCount / 2)
                 horizontalAlignment: Text.AlignHCenter
                 verticalAlignment: Text.AlignVCenter
                 font.pixelSize: fontMetrics.font.pixelSize * 1.25
             }
         }

         Frame {
             id: frame
             padding: 0
             anchors.centerIn: parent

             Row {
                 id: row

                 Tumbler {
                     id: hoursTumbler
                     model: 12
                     delegate: delegateComponent
                 }

                 Tumbler {
                     id: minutesTumbler
                     model: 60
                     delegate: delegateComponent
                 }

                 Tumbler {
                     id: amPmTumbler
                     model: ["AM", "PM"]
                     delegate: delegateComponent
                 }
             }
         }
     }

See also Customizing Tumbler and Input Controls.

## Property Documentation

count : int `[read-only]`

This property holds the number of items in the model.

currentIndex : int

This property holds the index of the current item.

The value of this property is `-1` when count is equal to `0`. In all other cases, it will be greater than or equal to `0`.

See also currentItem and positionViewAtIndex().

currentItem : Item `[read-only]`

This property holds the item at the current index.

See also currentIndex and positionViewAtIndex().

delegate : Component

This property holds the delegate used to display each item.

model : variant

This property holds the model that provides data for this tumbler.

moving : bool `[since QtQuick.Controls 2.2 (Qt 5.9)]`

This property describes whether the tumbler is currently moving, due to the user either dragging or flicking it.

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

visibleItemCount : int

This property holds the number of items visible in the tumbler. It must be an odd number, as the current item is always vertically centered.

wrap : bool `[since QtQuick.Controls 2.1 (Qt 5.8)]`

This property determines whether or not the tumbler wraps around when it reaches the top or bottom.

The default value is `false` when count is less than visibleItemCount, as it is simpler to interact with a non-wrapping Tumbler when there are only a few items. To override this behavior, explicitly set the value of this property. To return to the default behavior, set this property to `undefined`.

This property was introduced in QtQuick.Controls 2.1 (Qt 5.8).

## Attached Property Documentation

Tumbler.displacement : real `[read-only]`

This attached property holds a value from `-visibleItemCount / 2` to `visibleItemCount / 2`, which represents how far away this item is from being the current item, with `0` being completely current.

For example, the item below will be 40% opaque when it is not the current item, and transition to 100% opacity when it becomes the current item:

     delegate: Text {
         text: modelData
         opacity: 0.4 + Math.max(0, 1 - Math.abs(Tumbler.displacement)) * 0.6
     }

Tumbler.tumbler : Tumbler `[read-only]`

This attached property holds the tumbler. The property can be attached to a tumbler delegate. The value is `null` if the item is not a tumbler delegate.

## Method Documentation

`[since QtQuick.Controls 2.5 (Qt 5.12)]` void positionViewAtIndex(int index, PositionMode mode)

Positions the view so that the index is at the position specified by mode.

For example:

     positionViewAtIndex(10, Tumbler.Center)

If wrap is true (the default), the modes available to PathView's positionViewAtIndex() function are available, otherwise the modes available to ListView's positionViewAtIndex() function are available.

Note: There is a known limitation that using `Tumbler.Beginning` when wrap is `true` will result in the wrong item being positioned at the top of view. As a workaround, pass `index - 1`.

This method was introduced in QtQuick.Controls 2.5 (Qt 5.12).

See also currentIndex.