Class “CollectionView”

Object > NativeObject > Widget > Composite > CollectionView

A scrollable list that displays data items in cells, one per row. Cells are created on demand by the createCell callback and reused on scrolling.

CollectionView on Android
Android
CollectionView on iOS
iOS
Type: CollectionView<CellWidgetType> extends Composite<CellWidgetType>
Generics: CellWidgetType: The common widget class used for cells in this collectionView. It is recommended to use different classes for different cell types. Must be a subclass of Widget and defaults to Widget.
Constructor: public
Singleton: No
Namespace: tabris
Direct subclasses: ListView
JSX Support: Element: <CollectionView/>
Parent Elements: <Canvas/>, <Cell/>, <Composite/>, <Page/>, <RefreshComposite/>, <Row/>, <ScrollView/>, <Stack/>, <Tab/>
Child Elements: Not Supported

Examples

JavaScript

import {CollectionView, contentView, TextView} from 'tabris';

const items = ['Apple', 'Banana', 'Cherry'];

new CollectionView({
  left: 0, top: 0, right: 0, bottom: 0,
  itemCount: items.length,
  createCell: () => new TextView(),
  updateCell: (view, index) =>  {
    view.text = items[index];
  }
}).appendTo(contentView);

See also:

JSX Creating a simple CollectionView
JSX Creating a CollectionView with multiple cell types
JSX Creating a CollectionView with pull-to-refresh support
JSX Creating a CollectionView with sticky headers
JSX Creating a CollectionView with dynamic column count
JSX collectionview-cellheightauto.jsx
TSX collectionview-celltype-ts.tsx
TSX collectionview-scroll-ts.tsx
JSX collectionview-swipe-to-dismiss.jsx
TSX collectionview-ts.tsx

Constructor

new CollectionView(properties?)

Parameter Type Description
properties Properties<CollectionView> Sets all key-value pairs in the properties object as widget properties. Optional.

Methods

cellByItemIndex(itemIndex)

Returns the cell currently associated with the given item index. Returns null if the item is not currently displayed.

Parameter Type Description
itemIndex number The index of the item as given in updateCell.

Returns: CellWidgetType | null

insert(index, count?)

Inserts one or more items at the given index. When no count is specified, a single item will be added at the given index. New cells may be created if needed. The updateCell callback will only be called for those new items that become immediately visible. Note that inserting new items changes the index of all subsequent items. This operation will update the itemCount property.

Parameter Type Description
index number  
count number The position to insert the items at. A negative index is interpreted as relative to the end. If the given index is greater than the item count, new items will be appended at the end. Optional.

Returns: undefined

itemIndex(widget)

Determines the item index currently associated with the given cell.

Parameter Type Description
widget Widget A widget instance created by createCell, or a child of that widget.

Returns: number

load(itemCount)

Loads a new model with the given itemCount. This operation will update the itemCount property.

Parameter Type Description
itemCount number The number of items in the model to load.

Returns: undefined

refresh(index?)

Triggers an update of the item at the given index by calling the updateCell callback of the corresponding. If no index is given, all visible items will be updated.

Parameter Type Description
index number The index of the item that was changed. Optional.

Returns: undefined

remove(index, count?)

Removes one or more items beginning with the given index. When no count is given, only the item at index will be removed. Note that this changes the index of all subsequent items, however. This operation will update the itemCount property.

Parameter Type Description
index number The index of the first item to remove. A negative value is interpreted as relative to the end.
count number The number of items to remove. Optional.

Returns: undefined

reveal(index, options?)

Scrolls the item with the given index into view.

Parameter Type Description
index number The index of the item to reveal. If this is negative, it is interpreted as relative to the end
options {animate?: boolean, offset?: number} An additional object to control the animation.
  • animate allows to scroll to an item in an animated fashion. The animate property defaults to true when no options object is given.

  • offset shifts the targeted scroll position by a device independent pixel value. When offset is used the targeted reveal scroll position will start from the top of the CollectionView. Applying offset will perform the reveal() operation without an animation, ignoring the animate property. Optional.

Returns: undefined

Properties

cellHeight

The height of a collection cell. If set to 'auto', the cell height will be calculated individually for each cell. If set to a function, this function will be called for every item, providing the item index and the cell type as parameters, and must return the cell height for the given item. Note: On iOS "auto" may cause significant performance downgrade as it requires additional layouting passes to calculate cell height internally. If possible please use a combination of fixed itemHeight and cellType properties to specify different height for different cells.

Type: number
| 'auto'
| (index, cellType) => number | 'auto'
Default: 'auto'
Settable: Yes
Change Event: cellHeightChanged

cellType

The name of the cell type to use for the item at the given index. This name will be passed to the createCell and cellHeight callbacks. Cells will be reused only for those items that map to the same cell type. If set to a function, this function will be called for every item, providing the item index as a parameter, and must return a unique name for the cell type to use for the given item.

Type: string
| (index) => cellType
| null
Settable: Yes
Change Event: cellTypeChanged

See also:

TSX collectionview-celltype-ts.tsx
JSX collectionview-celltype.jsx

columnCount

The number of columns to display in the collection view. If set to a value n > 1, each row will contain n items. The available space will be equally distributed between columns.

Type: number
Default: 1
Settable: Yes
Change Event: columnCountChanged

See also:

JSX collectionview-columncount.jsx

createCell

A callback used to create a new reusable cell widget for a given type. This callback will be called by the framework and the created cell will be reused for different items. The created widget should be populated in the updateCell function.

Type: (cellType) => CellWidgetType
Settable: Yes
Change Event: createCellChanged

firstVisibleIndex

The index of the first item that is currently visible on screen.

Type: number
Settable: No
Change Event: firstVisibleIndexChanged

itemCount

The number of items to display. To add or remove items later, use the methods insert() and remove() instead of setting the itemCount. To display a new list of items, use the load() method.

Type: number
Settable: Yes
Change Event: itemCountChanged

lastVisibleIndex

The index of the last item that is currently visible on screen.

Type: number
Settable: No
Change Event: lastVisibleIndexChanged

refreshEnabled

Enables the user to trigger a refresh by using the pull-to-refresh gesture.

Type: boolean
Default: false
Settable: Yes
Change Event: refreshEnabledChanged

See also:

JSX collectionview-refreshenabled.jsx

refreshIndicator

Whether the refresh indicator is currently visible. Will be set to true when a refresh event is triggered. Reset it to false when the refresh is finished.

Type: boolean
Default: false
Settable: Yes
Change Event: refreshIndicatorChanged

refreshMessage

iOS

The message text displayed together with the refresh indicator.

Type: string
Default: (empty string)
Settable: Yes
Change Event: refreshMessageChanged

scrollbarVisible

Allows to show or hide the scroll bar. When the scroll bar is hidden, it will be briefly visible while scrolling.

Type: boolean
Default: true
Settable: Yes
Change Event: scrollbarVisibleChanged

updateCell

A callback used to update a given cell widget to display the item with the given index. This callback will be called by the framework.

Type: (cell, index) => void
Settable: Yes
Change Event: updateCellChanged

Events

refresh

Fired when the user requested a refresh. An event listener should reset the refreshIndicator property when refresh is finished.

EventObject Type: EventObject<CollectionView>

This event has no additional parameter.

scroll

Fired while the collection view is scrolling.

EventObject Type: CollectionViewScrollEvent<CollectionView>

Property Type Description
deltaX number Currently always 0.
deltaY number The delta of the scroll position. Positive when scrolling up and negative when scrolling down.

See also:

TSX collectionview-scroll-ts.tsx
JSX collectionview-scroll.jsx

Change Events

scrollbarVisibleChanged

Fired when the scrollbarVisible property has changed.

EventObject Type: PropertyChangedEvent<CollectionView, boolean>

Property Type Description
value boolean The new value of scrollbarVisible.

cellHeightChanged

Fired when the cellHeight property has changed.

EventObject Type: PropertyChangedEvent<CollectionView, number
| 'auto'
| Function>

Property Type Description
value number
| 'auto'
| (index, cellType) => number | 'auto'
The new value of cellHeight.

itemCountChanged

Fired when the itemCount property has changed.

EventObject Type: PropertyChangedEvent<CollectionView, number>

Property Type Description
value number The new value of itemCount.

createCellChanged

Fired when the createCell property has changed.

EventObject Type: PropertyChangedEvent<CollectionView, Function>

Property Type Description
value (cellType) => CellWidgetType The new value of createCell.

updateCellChanged

Fired when the updateCell property has changed.

EventObject Type: PropertyChangedEvent<CollectionView, Function>

Property Type Description
value (cell, index) => void The new value of updateCell.

cellTypeChanged

Fired when the cellType property has changed.

EventObject Type: PropertyChangedEvent<CollectionView, string
| Function
| null>

Property Type Description
value string
| (index) => cellType
| null
The new value of cellType.

refreshEnabledChanged

Fired when the refreshEnabled property has changed.

EventObject Type: PropertyChangedEvent<CollectionView, boolean>

Property Type Description
value boolean The new value of refreshEnabled.

refreshIndicatorChanged

Fired when the refreshIndicator property has changed.

EventObject Type: PropertyChangedEvent<CollectionView, boolean>

Property Type Description
value boolean The new value of refreshIndicator.

refreshMessageChanged

Fired when the refreshMessage property has changed.

EventObject Type: PropertyChangedEvent<CollectionView, string>

Property Type Description
value string The new value of refreshMessage.

firstVisibleIndexChanged

Fired when the firstVisibleIndex property has changed.

EventObject Type: PropertyChangedEvent<CollectionView, number>

Property Type Description
value number The new value of firstVisibleIndex.

lastVisibleIndexChanged

Fired when the lastVisibleIndex property has changed.

EventObject Type: PropertyChangedEvent<CollectionView, number>

Property Type Description
value number The new value of lastVisibleIndex.

columnCountChanged

Fired when the columnCount property has changed.

EventObject Type: PropertyChangedEvent<CollectionView, number>

Property Type Description
value number The new value of columnCount.