Instantiates a number of Item-based components using a provided model. 更多...
导入语句: | import QtQuick 2.2 |
继承: | Item |
The Repeater type is used to create a large number of similar items. Like other view types, a Repeater has a model 和 delegate : for each entry in the model, the delegate is instantiated in a context seeded with data from the model. A Repeater item is usually enclosed in a positioner type such as Row or Column to visually position the multiple delegate items created by the Repeater.
The following Repeater creates three instances of a Rectangle item within a Row :
import QtQuick 2.0 Row { Repeater { model: 3 Rectangle { width: 100; height: 40 border.width: 1 color: "yellow" } } }
A Repeater's model can be any of the supported data models . Additionally, like delegates for other views, a Repeater delegate can access its index within the repeater, as well as the model data relevant to the delegate. See the delegate property documentation for details.
Items instantiated by the Repeater are inserted, in order, as children of the Repeater's parent. The insertion starts immediately after the repeater's position in its parent stacking list. This allows a Repeater to be used inside a layout. For example, the following Repeater's items are stacked between a red rectangle and a blue rectangle:
Row { Rectangle { width: 10; height: 20; color: "red" } Repeater { model: 10 Rectangle { width: 20; height: 20; radius: 10; color: "green" } } Rectangle { width: 10; height: 20; color: "blue" } }
注意: A Repeater item owns all items it instantiates. Removing or dynamically destroying an item created by a Repeater results in unpredictable behavior.
The Repeater type creates all of its delegate items when the repeater is first created. This can be inefficient if there are a large number of delegate items and not all of the items are required to be visible at the same time. If this is the case, consider using other view types like ListView (which only creates delegate items when they are scrolled into view) or use the 动态对象创建 methods to create items as they are required.
Also, note that Repeater is Item -based, and can only repeat Item -derived objects. For example, it cannot be used to repeat QtObjects:
// bad code: Item { // Can't repeat QtObject as it doesn't derive from Item. Repeater { model: 10 QtObject {} } }
count : int |
This property holds the number of items in the model.
注意: The number of items in the model as reported by count may differ from the number of created delegates if the Repeater is in the process of instantiating delegates or is incorrectly set up.
[default] delegate : 组件 |
The delegate provides a template defining each item instantiated by the repeater.
Delegates are exposed to a read-only
index
property that indicates the index of the delegate within the repeater. For example, the following
文本
delegate displays the index of each repeated item:
Column { Repeater { model: 10 Text { text: "I'm item " + index } } } |
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若
model
是
string list
or
object list
, the delegate is also exposed to a read-only
modelData
property that holds the string or object data. For example:
Column { Repeater { model: ["apples", "oranges", "pears"] Text { text: "Data: " + modelData } } } |
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若 model is a model object (such as a ListModel ) the delegate can access all model roles as named properties, in the same way that delegates do for view classes like ListView .
另请参阅 QML Data Models .
model : any |
The model providing data for the repeater.
This property can be set to any of the supported data models :
The type of model affects the properties that are exposed to the delegate .
另请参阅 数据模型 .
itemAdded ( int index , Item item ) |
This signal is emitted when an item is added to the repeater. The index parameter holds the index at which the item has been inserted within the repeater, and the item parameter holds the Item that has been added.
注意:
相应处理程序是
onItemAdded
.
itemRemoved ( int index , Item item ) |
This signal is emitted when an item is removed from the repeater. The index parameter holds the index at which the item was removed from the repeater, and the item parameter holds the Item that was removed.
Do not keep a reference to item if it was created by this repeater, as in these cases it will be deleted shortly after the signal is handled.
注意:
相应处理程序是
onItemRemoved
.
Item itemAt ( index ) |
返回
Item
that has been created at the given
index
,或
null
if no item exists at
index
.