内容

特性
附加特性
附加信号
方法
详细描述
用法范例

ListView QML Element

The ListView item provides a list view of items provided by a model. 更多...

Since:	Qt 4.7
继承：	Flickable

所有成员列表，包括继承成员

特性

cacheBuffer : int
count : int
currentIndex : int
currentItem : Item
currentSection : string
delegate : Component
footer : Component
header : Component
highlight : Component
highlightFollowsCurrentItem : bool
highlightItem : Item
highlightMoveDuration : int
highlightMoveSpeed : real
highlightRangeMode : enumeration
highlightResizeDuration : int
highlightResizeSpeed : real
keyNavigationWraps : bool
layoutDirection : enumeration
model : model
orientation : enumeration
preferredHighlightBegin : real
preferredHighlightEnd : real
section
- section.property : string
- section.criteria : enumeration
- section.delegate : Component
snapMode : enumeration
spacing : real

附加特性

delayRemove : bool
isCurrentItem : bool
nextSection : string
previousSection : string
section : string
view : ListView

附加信号

onAdd ()
onRemove ()

方法

decrementCurrentIndex ()
incrementCurrentIndex ()
int indexAt (int x , int y )
positionViewAtBeginning ()
positionViewAtEnd ()
positionViewAtIndex (int index , PositionMode mode )

详细描述

A ListView displays data from models created from built-in QML elements like ListModel and XmlListModel , or custom model classes defined in C++ that inherit from QAbstractListModel .

A ListView 拥有 model , which defines the data to be displayed, and a delegate , which defines how the data should be displayed. Items in a ListView are laid out horizontally or vertically. List views are inherently flickable because ListView 继承自 Flickable .

用法范例

The following example shows the definition of a simple list model defined in a file called ContactModel.qml :

import QtQuick 1.0
ListModel {
    ListElement {
        name: "Bill Smith"
        number: "555 3264"
    }
    ListElement {
        name: "John Brown"
        number: "555 8426"
    }
    ListElement {
        name: "Sam Wise"
        number: "555 0473"
    }
}

Another component can display this model data in a ListView ，像这样：

import QtQuick 1.0
ListView {
    width: 180; height: 200
    model: ContactModel {}
    delegate: Text {
        text: name + ": " + number
    }
}

在这里， ListView 创建 ContactModel component for its model, and a Text element for its delegate. The view will create a new Text component for each item in the model. Notice the delegate is able to access the model's 名称 and 编号 data directly.

An improved list view is shown below. The delegate is visually improved and is moved into a separate contactDelegate 组件。

Rectangle {
    width: 180; height: 200
    Component {
        id: contactDelegate
        Item {
            width: 180; height: 40
            Column {
                Text { text: '<b>Name:</b> ' + name }
                Text { text: '<b>Number:</b> ' + number }
            }
        }
    }
    ListView {
        anchors.fill: parent
        model: ContactModel {}
        delegate: contactDelegate
        highlight: Rectangle { color: "lightsteelblue"; radius: 5 }
        focus: true
    }
}

The currently selected item is highlighted with a blue Rectangle 使用 highlight property, and focus 被设为 true to enable keyboard navigation for the list view. The list view itself is a focus scope (see the focus documentation page 了解更多细节)。

Delegates are instantiated as needed and may be destroyed at any time. State should never be stored in a delegate.

ListView attaches a number of properties to the root item of the delegate, for example ListView.isCurrentItem . In the following example, the root delegate item can access this attached property directly as ListView.isCurrentItem , while the child contactInfo object must refer to this property as wrapper.ListView.isCurrentItem .

ListView {
    width: 180; height: 200
    Component {
        id: contactsDelegate
        Rectangle {
            id: wrapper
            width: 180
            height: contactInfo.height
            color: ListView.isCurrentItem ? "black" : "red"
            Text {
                id: contactInfo
                text: name + ": " + number
                color: wrapper.ListView.isCurrentItem ? "red" : "black"
            }
        }
    }
    model: ContactModel {}
    delegate: contactsDelegate
    focus: true
}

注意： Views do not enable clip automatically. If the view is not clipped by another item or the screen, it will be necessary to set clip: true in order to have the out of view items clipped nicely.

另请参阅 QML Data Models , GridView ，和 ListView examples .

特性文档编制

cacheBuffer : int

This property determines whether delegates are retained outside the visible area of the view.

If this value is non-zero, the view keeps as many delegates instantiated as it can fit within the buffer specified. For example, if in a vertical view the delegate is 20 pixels high and cacheBuffer is set to 40, then up to 2 delegates above and 2 delegates below the visible area may be retained.

Note that cacheBuffer is not a pixel buffer - it only maintains additional instantiated delegates.

Setting this value can improve the smoothness of scrolling behavior at the expense of additional memory usage. It is not a substitute for creating efficient delegates; the fewer elements in a delegate, the faster a view can be scrolled.

count : int

This property holds the number of items in the view.

currentIndex : int

The currentIndex property holds the index of the current item, and currentItem holds the current item. Setting the currentIndex to -1 will clear the highlight and set currentItem to null.

若 highlightFollowsCurrentItem is true , setting either of these properties will smoothly scroll the ListView so that the current item becomes visible.

Note that the position of the current item may only be approximate until it becomes visible in the view.

currentItem : Item

The currentIndex property holds the index of the current item, and currentItem holds the current item. Setting the currentIndex to -1 will clear the highlight and set currentItem to null.

若 highlightFollowsCurrentItem is true , setting either of these properties will smoothly scroll the ListView so that the current item becomes visible.

Note that the position of the current item may only be approximate until it becomes visible in the view.

currentSection : string

This property holds the section that is currently at the beginning of the view.

delegate : Component

The delegate provides a template defining each item instantiated by the view. The index is exposed as an accessible index property. Properties of the model are also available depending upon the type of Data Model .

The number of elements in the delegate has a direct effect on the flicking performance of the view. If at all possible, place functionality that is not needed for the normal display of the delegate in a Loader which can load additional elements when needed.

The ListView will lay out the items based on the size of the root item in the delegate.

It is recommended that the delagate's size be a whole number to avoid sub-pixel alignment of items.

注意： Delegates are instantiated as needed and may be destroyed at any time. State should never be stored in a delegate.

This property holds the component to use as the footer.

An instance of the footer component is created for each view. The footer is positioned at the end of the view, after any items.

另请参阅 header .

header : Component

This property holds the component to use as the header.

An instance of the header component is created for each view. The header is positioned at the beginning of the view, before any items.

另请参阅 footer .

highlight : Component

This property holds the component to use as the highlight.

An instance of the highlight component is created for each list. The geometry of the resulting component instance is managed by the list so as to stay with the current item, unless the highlightFollowsCurrentItem property is false.

另请参阅 highlightItem , highlightFollowsCurrentItem ，和 ListView examples .

highlightFollowsCurrentItem : bool

This property holds whether the highlight is managed by the view.

If this property is true (the default value), the highlight is moved smoothly to follow the current item. Otherwise, the highlight is not moved by the view, and any movement must be implemented by the highlight.

Here is a highlight with its motion defined by a SpringAnimation item:

Component {
    id: highlight
    Rectangle {
        width: 180; height: 40
        color: "lightsteelblue"; radius: 5
        y: list.currentItem.y
        Behavior on y {
            SpringAnimation {
                spring: 3
                damping: 0.2
            }
        }
    }
}
ListView {
    id: list
    width: 180; height: 200
    model: ContactModel {}
    delegate: Text { text: name }
    highlight: highlight
    highlightFollowsCurrentItem: false
    focus: true
}

Note that the highlight animation also affects the way that the view is scrolled. This is because the view moves to maintain the highlight within the preferred highlight range (or visible viewport).

另请参阅 highlight and highlightMoveSpeed .

highlightItem : Item

This holds the highlight item created from the highlight 组件。

The highlightItem is managed by the view unless highlightFollowsCurrentItem 被设为 false。

另请参阅 highlight and highlightFollowsCurrentItem .

highlightMoveDuration : int

These properties hold the move and resize animation speed of the highlight delegate.

highlightFollowsCurrentItem must be true for these properties to have effect.

The default value for the speed properties is 400 pixels/second. The default value for the duration properties is -1, i.e. the highlight will take as much time as necessary to move at the set speed.

These properties have the same characteristics as a SmoothedAnimation .

另请参阅 highlightFollowsCurrentItem .

highlightMoveSpeed : real

These properties hold the move and resize animation speed of the highlight delegate.

highlightFollowsCurrentItem must be true for these properties to have effect.

The default value for the speed properties is 400 pixels/second. The default value for the duration properties is -1, i.e. the highlight will take as much time as necessary to move at the set speed.

These properties have the same characteristics as a SmoothedAnimation .

另请参阅 highlightFollowsCurrentItem .

highlightRangeMode : enumeration

These properties define the preferred range of the highlight (for the current item) within the view. The preferredHighlightBegin value must be less than the preferredHighlightEnd 值。

These properties affect the position of the current item when the list is scrolled. For example, if the currently selected item should stay in the middle of the list when the view is scrolled, set the preferredHighlightBegin and preferredHighlightEnd values to the top and bottom coordinates of where the middle item would be. If the currentItem is changed programmatically, the list will automatically scroll so that the current item is in the middle of the view. Furthermore, the behavior of the current item index will occur whether or not a highlight exists.

Valid values for highlightRangeMode 是：

ListView .ApplyRange - the view attempts to maintain the highlight within the range. However, the highlight can move outside of the range at the ends of the list or due to mouse interaction.
ListView .StrictlyEnforceRange - the highlight never moves outside of the range. The current item changes if a keyboard or mouse action would cause the highlight to move outside of the range.
ListView .NoHighlightRange - this is the default value.

highlightResizeDuration : int

These properties hold the move and resize animation speed of the highlight delegate.

highlightFollowsCurrentItem must be true for these properties to have effect.

The default value for the speed properties is 400 pixels/second. The default value for the duration properties is -1, i.e. the highlight will take as much time as necessary to move at the set speed.

These properties have the same characteristics as a SmoothedAnimation .

另请参阅 highlightFollowsCurrentItem .

highlightResizeSpeed : real

These properties hold the move and resize animation speed of the highlight delegate.

highlightFollowsCurrentItem must be true for these properties to have effect.

The default value for the speed properties is 400 pixels/second. The default value for the duration properties is -1, i.e. the highlight will take as much time as necessary to move at the set speed.

These properties have the same characteristics as a SmoothedAnimation .

另请参阅 highlightFollowsCurrentItem .

keyNavigationWraps : bool

This property holds whether the list wraps key navigation.

If this is true, key navigation that would move the current item selection past the end of the list instead wraps around and moves the selection to the start of the list, and vice-versa.

By default, key navigation is not wrapped.

layoutDirection : enumeration

This property holds the layout direction of the horizontal list.

可能的值：

Qt.LeftToRight (default) - Items will be laid out from left to right.
Qt.RightToLeft - Items will be laid out from right to let.

When using the attached property LayoutMirroring::enabled for locale layouts, the layout direction of the horizontal list will be mirrored. However, the actual property layoutDirection will remain unchanged. You can use the property LayoutMirroring::enabled to determine whether the direction has been mirrored.

另请参阅 LayoutMirroring .

model : model

This property holds the model providing data for the list.

The model provides the set of data that is used to create the items in the view. Models can be created directly in QML using ListModel , XmlListModel or VisualItemModel , or provided by C++ model classes. If a C++ model class is used, it must be a subclass of QAbstractItemModel or a simple list.

另请参阅 数据模型 .

orientation : enumeration

This property holds the orientation of the list.

可能的值：

ListView .Horizontal - Items are laid out horizontally
ListView .Vertical (default) - Items are laid out vertically

Horizontal orientation:

Vertical orientation:

preferredHighlightBegin : real

These properties define the preferred range of the highlight (for the current item) within the view. The preferredHighlightBegin value must be less than the preferredHighlightEnd 值。

Valid values for highlightRangeMode 是：

ListView .ApplyRange - the view attempts to maintain the highlight within the range. However, the highlight can move outside of the range at the ends of the list or due to mouse interaction.
ListView .StrictlyEnforceRange - the highlight never moves outside of the range. The current item changes if a keyboard or mouse action would cause the highlight to move outside of the range.
ListView .NoHighlightRange - this is the default value.

preferredHighlightEnd : real

These properties define the preferred range of the highlight (for the current item) within the view. The preferredHighlightBegin value must be less than the preferredHighlightEnd 值。

Valid values for highlightRangeMode 是：

ListView .ApplyRange - the view attempts to maintain the highlight within the range. However, the highlight can move outside of the range at the ends of the list or due to mouse interaction.
ListView .StrictlyEnforceRange - the highlight never moves outside of the range. The current item changes if a keyboard or mouse action would cause the highlight to move outside of the range.
ListView .NoHighlightRange - this is the default value.

section group
section.property : string
section.criteria : enumeration
section.delegate : Component

These properties hold the expression to be evaluated for the section attached property.

The section attached property enables a ListView to be visually separated into different parts. These properties determine how sections are created.

section.property holds the name of the property that is the basis of each section.

section.criteria holds the criteria for forming each section based on section.property . This value can be one of:

ViewSection.FullString (default) - sections are created based on the section.property 值。
ViewSection.FirstCharacter - sections are created based on the first character of the section.property value (for example, 'A', 'B', 'C' sections, etc. for an address book)

section.delegate holds the delegate component for each section.

Each item in the list has attached properties named ListView.section , ListView.previousSection and ListView.nextSection . These may be used to place a section header for related items.

For example, here is a ListView that displays a list of animals, separated into sections. Each item in the ListView is placed in a different section depending on the "size" property of the model item. The sectionHeading delegate component provides the light blue bar that marks the beginning of each section.

注意： Adding sections to a ListView does not automatically re-order the list items by the section criteria. If the model is not ordered by section, then it is possible that the sections created will not be unique; each boundary between differing sections will result in a section header being created even if that section exists elsewhere.

另请参阅 ListView examples .

snapMode : enumeration

This property determines how the view scrolling will settle following a drag or flick. The possible values are:

ListView .NoSnap (default) - the view stops anywhere within the visible area.
ListView .SnapToItem - the view settles with an item aligned with the start of the view.
ListView .SnapOneItem - the view settles no more than one item away from the first visible item at the time the mouse button is released. This mode is particularly useful for moving one page at a time.

snapMode does not affect the currentIndex . To update the currentIndex as the list is moved, set highlightRangeMode to ListView.StrictlyEnforceRange .

另请参阅 highlightRangeMode .

spacing : real

This property holds the spacing between items.

默认值为 0。