ComboBox QML Type | Qt Quick Controls 6.3.1

- Qt 6.3
- Qt Quick Controls
- QML Types
- ComboBox
- Qt 6.3.1 Reference Documentation

# ComboBox QML Type

Combined button and popup list for selecting options. More...

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

- List of all members, including inherited members

## Properties

- acceptableInput : bool
- count : int
- currentIndex : int
- currentText : string
- currentValue : var
- delegate : Component
- displayText : string
- down : bool
- editText : string
- editable : bool
- flat : bool
- highlightedIndex : int
- implicitContentWidthPolicy : enumeration
- implicitIndicatorHeight : real
- implicitIndicatorWidth : real
- indicator : Item
- inputMethodComposing : bool
- inputMethodHints : flags
- model : model
- popup : Popup
- pressed : bool
- selectTextByMouse : bool
- textRole : string
- validator : Validator
- valueRole : string

## Signals

- void accepted()
- void activated(int index)
- void highlighted(int index)

## Methods

- void decrementCurrentIndex()
- int find(string text, enumeration flags)
- void incrementCurrentIndex()
- int indexOfValue(object value)
- void selectAll()
- string textAt(int index)
- var valueAt(int index)

## Detailed Description

ComboBox is a combined button and popup list. It provides a means of presenting a list of options to the user in a way that takes up the minimum amount of screen space.

ComboBox is populated with a data model. The data model is commonly a JavaScript array, a ListModel or an integer, but other types of data models are also supported.

     ComboBox {
         model: ["First", "Second", "Third"]
     }

## Editable ComboBox

ComboBox can be made editable. An editable combo box auto-completes its text based on what is available in the model.

The following example demonstrates appending content to an editable combo box by reacting to the accepted signal.

     ComboBox {
         editable: true
         model: ListModel {
             id: model
             ListElement { text: "Banana" }
             ListElement { text: "Apple" }
             ListElement { text: "Coconut" }
         }
         onAccepted: {
             if (find(editText) === -1)
                 model.append({text: editText})
         }
     }

## ComboBox's Popup

By default, clicking outside of ComboBox's popup will close it, and the event is propagated to items lower in the stacking order. To prevent the popup from closing, set its closePolicy:

         popup.closePolicy: Popup.CloseOnEscape

To prevent event propagation, set its modal property to `true`:

         popup.modal: true

## ComboBox Model Roles

ComboBox is able to visualize standard data models that provide the `modelData` role:

- models that have only one role
- models that do not have named roles (JavaScript array, integer)

When using models that have multiple named roles, ComboBox must be configured to use a specific text role for its display text and delegate instances. If you want to use a role of the model item that corresponds to the text role, set valueRole. The currentValue property and indexOfValue() method can then be used to get information about those values.

For example:

     ApplicationWindow {
         width: 640
         height: 480
         visible: true

         // Used as an example of a backend - this would usually be
         // e.g. a C++ type exposed to QML.
         QtObject {
             id: backend
             property int modifier
         }

         ComboBox {
             textRole: "text"
             valueRole: "value"
             // When an item is selected, update the backend.
             onActivated: backend.modifier = currentValue
             // Set the initial currentIndex to the value stored in the backend.
             Component.onCompleted: currentIndex = indexOfValue(backend.modifier)
             model: [
                 { value: Qt.NoModifier, text: qsTr("No modifier") },
                 { value: Qt.ShiftModifier, text: qsTr("Shift") },
                 { value: Qt.ControlModifier, text: qsTr("Control") }
             ]
         }
     }

Note: If ComboBox is assigned a data model that has multiple named roles, but textRole is not defined, ComboBox is unable to visualize it and throws a `ReferenceError: modelData is not defined`.

See also Customizing ComboBox, Input Controls, and Focus Management in Qt Quick Controls.

## Property Documentation

[read-only, since QtQuick.Controls 2.2 (Qt 5.9)] acceptableInput : bool

This property holds whether the combo box contains acceptable text in the editable text field.

If a validator has been set, the value is `true` only if the current text is acceptable to the validator as a final string (not as an intermediate string).

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

See also validator and accepted.

[read-only] count : int

This property holds the number of items in the combo box.

currentIndex : int

This property holds the index of the current item in the combo box.

The default value is `-1` when count is `0`, and `0` otherwise.

See also activated(), currentText, and highlightedIndex.

[read-only] currentText : string

This property holds the text of the current item in the combo box.

See also currentIndex, displayText, textRole, and editText.

[read-only, since QtQuick.Controls 2.14 (Qt 5.14)] currentValue : var

This property holds the value of the current item in the combo box.

For an example of how to use this property, see ComboBox Model Roles.

This property was introduced in QtQuick.Controls 2.14 (Qt 5.14).

See also currentIndex, currentText, and valueRole.

delegate : Component

This property holds a delegate that presents an item in the combo box popup.

It is recommended to use ItemDelegate (or any other AbstractButton derivatives) as the delegate. This ensures that the interaction works as expected, and the popup will automatically close when appropriate. When other types are used as the delegate, the popup must be closed manually. For example, if MouseArea is used:

     delegate: Rectangle {
         // ...
         MouseArea {
             // ...
             onClicked: comboBox.popup.close()
         }
     }

See also ItemDelegate and Customizing ComboBox.

displayText : string

This property holds the text that is displayed on the combo box button.

By default, the display text presents the current selection. That is, it follows the text of the current item. However, the default display text can be overridden with a custom value.

     ComboBox {
         currentIndex: 1
         displayText: "Size: " + currentText
         model: ["S", "M", "L"]
     }

See also currentText and textRole.

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

This property holds whether the combo box button is visually down.

Unless explicitly set, this property is `true` when either `pressed` or `popup.visible` is `true`. To return to the default value, set this property to `undefined`.

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

See also pressed and popup.

[since QtQuick.Controls 2.2 (Qt 5.9)] editText : string

This property holds the text in the text field of an editable combo box.

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

See also editable, currentText, and displayText.

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

This property holds whether the combo box is editable.

The default value is `false`.

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

See also validator.

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

This property holds whether the combo box button is flat.

A flat combo box button does not draw a background unless it is interacted with. In comparison to normal combo boxes, flat combo boxes provide looks that make them stand out less from the rest of the UI. For instance, when placing a combo box into a tool bar, it may be desirable to make the combo box flat so it matches better with the flat looks of tool buttons.

The default value is `false`.

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

[read-only] highlightedIndex : int

This property holds the index of the highlighted item in the combo box popup list.

When a highlighted item is activated, the popup is closed, currentIndex is set to `highlightedIndex`, and the value of this property is reset to `-1`, as there is no longer a highlighted item.

See also highlighted() and currentIndex.

[since QtQuick.Controls 6.0 (Qt 6.0)] implicitContentWidthPolicy : enumeration

This property controls how the implicitContentWidth of the ComboBox is calculated.

When the width of a ComboBox is not large enough to display text, that text is elided. Depending on which parts of the text are elided, this can make selecting an item difficult for the end user. An efficient way of ensuring that a ComboBox is wide enough to avoid text being elided is to set a width that is known to be large enough:

     width: 300
     implicitContentWidthPolicy: ComboBox.ContentItemImplicitWidth

However, it is often not possible to know whether or not a hard-coded value will be large enough, as the size of text depends on many factors, such as font family, font size, translations, and so on.

implicitContentWidthPolicy provides an easy way to control how the implicitContentWidth is calculated, which in turn affects the implicitWidth of the ComboBox and ensures that text will not be elided.

The available values are:

Constant | Description
--- | ---
`ContentItemImplicitWidth` | The implicitContentWidth will default to that of the contentItem. This is the most efficient option, as no extra text layout is done.
`WidestText` | The implicitContentWidth will be set to the implicit width of the the largest text for the given textRole every time the model changes. This option should be used with smaller models, as it can be expensive.
`WidestTextWhenCompleted` | The implicitContentWidth will be set to the implicit width of the the largest text for the given textRole once after component completion. This option should be used with smaller models, as it can be expensive.

The default value is `ContentItemImplicitWidth`.

As this property only affects the `implicitWidth` of the ComboBox, setting an explicit width can still result in eliding.

Note: This feature requires the contentItem to be a type derived from TextInput.

Note: This feature requires text to be laid out, and can therefore be expensive for large models or models whose contents are updated frequently.

This property was introduced in QtQuick.Controls 6.0 (Qt 6.0).

[read-only, since QtQuick.Controls 2.5 (Qt 5.12)] implicitIndicatorHeight : real

This property holds the implicit indicator height.

The value is equal to `indicator ? indicator.implicitHeight : 0`.

This is typically used, together with implicitContentHeight and implicitBackgroundHeight, to calculate the implicitHeight.

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

See also implicitIndicatorWidth.

[read-only, since QtQuick.Controls 2.5 (Qt 5.12)] implicitIndicatorWidth : real

This property holds the implicit indicator width.

The value is equal to `indicator ? indicator.implicitWidth : 0`.

This is typically used, together with implicitContentWidth and implicitBackgroundWidth, to calculate the implicitWidth.

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

See also implicitIndicatorHeight.

indicator : Item

This property holds the drop indicator item.

See also Customizing ComboBox.

[read-only, since QtQuick.Controls 2.2 (Qt 5.9)] inputMethodComposing : bool

This property holds whether an editable combo box has partial text input from an input method.

While it is composing, an input method may rely on mouse or key events from the combo box to edit or commit the partial text. This property can be used to determine when to disable event handlers that may interfere with the correct operation of an input method.

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

[since QtQuick.Controls 2.2 (Qt 5.9)] inputMethodHints : flags

Provides hints to the input method about the expected content of the combo box and how it should operate.

The default value is `Qt.ImhNoPredictiveText`.

The value is a bit-wise combination of flags or `Qt.ImhNone` if no hints are set.

Flags that alter behavior are:

- Qt.ImhHiddenText - Characters should be hidden, as is typically used when entering passwords.
- Qt.ImhSensitiveData - Typed text should not be stored by the active input method in any persistent storage like predictive user dictionary.
- Qt.ImhNoAutoUppercase - The input method should not try to automatically switch to upper case when a sentence ends.
- Qt.ImhPreferNumbers - Numbers are preferred (but not required).
- Qt.ImhPreferUppercase - Upper case letters are preferred (but not required).
- Qt.ImhPreferLowercase - Lower case letters are preferred (but not required).
- Qt.ImhNoPredictiveText - Do not use predictive text (i.e. dictionary lookup) while typing.
- Qt.ImhDate - The text editor functions as a date field.
- Qt.ImhTime - The text editor functions as a time field.

Flags that restrict input (exclusive flags) are:

- Qt.ImhDigitsOnly - Only digits are allowed.
- Qt.ImhFormattedNumbersOnly - Only number input is allowed. This includes decimal point and minus sign.
- Qt.ImhUppercaseOnly - Only upper case letter input is allowed.
- Qt.ImhLowercaseOnly - Only lower case letter input is allowed.
- Qt.ImhDialableCharactersOnly - Only characters suitable for phone dialing are allowed.
- Qt.ImhEmailCharactersOnly - Only characters suitable for email addresses are allowed.
- Qt.ImhUrlCharactersOnly - Only characters suitable for URLs are allowed.

Masks:

- Qt.ImhExclusiveInputMask - This mask yields nonzero if any of the exclusive flags are used.

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

model : model

This property holds the model providing data for the combo box.

     ComboBox {
         textRole: "key"
         model: ListModel {
             ListElement { key: "First"; value: 123 }
             ListElement { key: "Second"; value: 456 }
             ListElement { key: "Third"; value: 789 }
         }
     }

See also textRole and Data Models.

popup : Popup

This property holds the popup.

The popup can be opened or closed manually, if necessary:

     onSpecialEvent: comboBox.popup.close()

See also Customizing ComboBox.

[read-only] pressed : bool

This property holds whether the combo box button is physically pressed. A button can be pressed by either touch or key events.

See also down.

[since QtQuick.Controls 2.15 (Qt 5.15)] selectTextByMouse : bool

This property holds whether the text field for an editable ComboBox can be selected with the mouse.

The default value is `false`.

This property was introduced in QtQuick.Controls 2.15 (Qt 5.15).

textRole : string

This property holds the model role used for populating the combo box.

When the model has multiple roles, `textRole` can be set to determine which role should be displayed.

See also model, currentText, displayText, and ComboBox Model Roles.

[since QtQuick.Controls 2.2 (Qt 5.9)] validator : Validator

This property holds an input text validator for an editable combo box.

When a validator is set, the text field will only accept input which leaves the text property in an intermediate state. The accepted signal will only be emitted if the text is in an acceptable state when the Return or Enter key is pressed.

The currently supported validators are IntValidator, DoubleValidator, and RegularExpressionValidator. An example of using validators is shown below, which allows input of integers between `0` and `10` into the text field:

     ComboBox {
         model: 10
         editable: true
         validator: IntValidator {
             top: 9
             bottom: 0
         }
     }

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

See also acceptableInput, accepted, and editable.

[since QtQuick.Controls 2.14 (Qt 5.14)] valueRole : string

This property holds the model role used for storing the value associated with each item in the model.

For an example of how to use this property, see ComboBox Model Roles.

This property was introduced in QtQuick.Controls 2.14 (Qt 5.14).

See also model and currentValue.

## Signal Documentation

`[since QtQuick.Controls 2.2 (Qt 5.9)]` void accepted()

This signal is emitted when the Return or Enter key is pressed on an editable combo box.

You can handle this signal in order to add the newly entered item to the model, for example:

     ComboBox {
         editable: true
         model: ListModel {
             id: model
             ListElement { text: "Banana" }
             ListElement { text: "Apple" }
             ListElement { text: "Coconut" }
         }
         onAccepted: {
             if (find(editText) === -1)
                 model.append({text: editText})
         }
     }

Before the signal is emitted, a check is done to see if the string exists in the model. If it does, currentIndex will be set to its index, and currentText to the string itself.

After the signal has been emitted, and if the first check failed (that is, the item did not exist), another check will be done to see if the item was added by the signal handler. If it was, the currentIndex and currentText are updated accordingly. Otherwise, they will be set to `-1` and `""`, respectively.

Note: If there is a validator set on the combo box, the signal will only be emitted if the input is in an acceptable state.

Note: The corresponding handler is `onAccepted`.

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

void activated(int index)

This signal is emitted when the item at index is activated by the user.

An item is activated when it is selected while the popup is open, causing the popup to close (and currentIndex to change), or while the popup is closed and the combo box is navigated via keyboard, causing the currentIndex to change. The currentIndex property is set to index.

Note: The corresponding handler is `onActivated`.

See also currentIndex.

void highlighted(int index)

This signal is emitted when the item at index in the popup list is highlighted by the user.

The highlighted signal is only emitted when the popup is open and an item is highlighted, but not necessarily activated.

Note: The corresponding handler is `onHighlighted`.

See also highlightedIndex.

## Method Documentation

void decrementCurrentIndex()

Decrements the current index of the combo box, or the highlighted index if the popup list is visible.

See also currentIndex and highlightedIndex.

int find(string text, enumeration flags)

Returns the index of the specified text, or `-1` if no match is found.

The way the search is performed is defined by the specified match flags. By default, combo box performs case sensitive exact matching (`Qt.MatchExactly`). All other match types are case-insensitive unless the `Qt.MatchCaseSensitive` flag is also specified.

Constant | Description
--- | ---
`Qt.MatchExactly` | The search term matches exactly (default).
`Qt.MatchRegularExpression` | The search term matches as a regular expression.
`Qt.MatchWildcard` | The search term matches using wildcards.
`Qt.MatchFixedString` | The search term matches as a fixed string.
`Qt.MatchStartsWith` | The search term matches the start of the item.
`Qt.MatchEndsWidth` | The search term matches the end of the item.
`Qt.MatchContains` | The search term is contained in the item.
`Qt.MatchCaseSensitive` | The search is case sensitive.

Note: This function can only be used after Component.completed() is emitted for the ComboBox.

For example:

     ComboBox {
         model: ListModel {
             ListElement { text: "Banana" }
             ListElement { text: "Apple" }
             ListElement { text: "Coconut" }
         }
         Component.onCompleted: currentIndex = find("Coconut")
     }

See also textRole.

void incrementCurrentIndex()

Increments the current index of the combo box, or the highlighted index if the popup list is visible.

See also currentIndex and highlightedIndex.

`[since QtQuick.Controls 2.14 (Qt 5.14)]` int indexOfValue(object value)

Returns the index of the specified value, or `-1` if no match is found.

For an example of how to use this method, see ComboBox Model Roles.

Note: This function can only be used after Component.completed() is emitted for the ComboBox.

This method was introduced in QtQuick.Controls 2.14 (Qt 5.14).

See also find(), currentValue, currentIndex, valueRole, and valueAt.

`[since QtQuick.Controls 2.2 (Qt 5.9)]` void selectAll()

Selects all the text in the editable text field of the combo box.

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

See also editText.

string textAt(int index)

Returns the text for the specified index, or an empty string if the index is out of bounds.

Note: This function can only be used after Component.completed() is emitted for the ComboBox.

For example:

     ComboBox {
         model: ListModel {
             ListElement { text: "Banana" }
             ListElement { text: "Apple" }
             ListElement { text: "Coconut" }
         }
         onActivated: (index) => { print(textAt(index)) }
     }

See also textRole.

`[since QtQuick.Controls 2.14 (Qt 5.14)]` var valueAt(int index)

Returns the value at position index in the combo box.

This method was introduced in QtQuick.Controls 2.14 (Qt 5.14).

See also indexOfValue.