Package com.vaadin.flow.component.grid.dataview

Class GridLazyDataView<T>

java.lang.Object

com.vaadin.flow.data.provider.AbstractDataView<T>

com.vaadin.flow.data.provider.AbstractLazyDataView<T>

com.vaadin.flow.component.grid.dataview.GridLazyDataView<T>

Type Parameters:

T - the type of the items in grid

All Implemented Interfaces:

DataView<T>, LazyDataView<T>, Serializable

public class GridLazyDataView<T>
extends AbstractLazyDataView<T>

Data view implementation for Grid with lazy data fetching. Provides information on the data and allows operations on it.

See Also:

• Serialized Form

Field Summary

Fields inherited from class com.vaadin.flow.data.provider.AbstractDataView

component, dataProviderSupplier, NULL_IDENTIFIER_ERROR_MESSAGE, NULL_ITEM_ERROR_MESSAGE

Constructor Summary

Constructors

Constructor	Description
GridLazyDataView(DataCommunicator<T> dataCommunicator, Grid<T> component)	Creates a new lazy data view for grid and verifies the passed data provider is compatible with this data view implementation.

Method Summary

Modifier and Type	Method	Description
void	setItemCountCallback(CallbackDataProvider.CountCallback<T,Void> callback)	Sets a callback that the Grid uses to get the exact item count in the backend.
void	setItemCountEstimate(int itemCountEstimate)	Sets the estimated item count for the component.
void	setItemCountFromDataProvider()	Switches the component to get the exact item count from the data provider's DataProvider.size(Query).
void	setItemCountUnknown()	Switches the component to automatically extend the number of items as the previous end is almost reached.

Methods inherited from class com.vaadin.flow.data.provider.AbstractLazyDataView

getDataCommunicator, getItem, getItemCountEstimate, getItemCountEstimateIncrease, getItems, getSupportedDataProviderType, setItemCountEstimateIncrease

Methods inherited from class com.vaadin.flow.data.provider.AbstractDataView

addIdentifierProviderChangeListener, addItemCountChangeListener, equals, getIdentifierProvider, refreshAll, refreshItem, setIdentifierProvider, verifyDataProviderType

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface com.vaadin.flow.data.provider.DataView

addItemCountChangeListener, refreshAll, refreshItem, setIdentifierProvider

Constructor Details

GridLazyDataView

public GridLazyDataView(DataCommunicator<T> dataCommunicator,
 Grid<T> component)

Creates a new lazy data view for grid and verifies the passed data provider is compatible with this data view implementation.

Parameters:

dataCommunicator - the data communicator of the component

component - the grid

Method Details

setItemCountCallback

public void setItemCountCallback(CallbackDataProvider.CountCallback<T,Void> callback)

Sets a callback that the Grid uses to get the exact item count in the backend. Use this when it is cheap to get the exact item count and it is desired that the user sees the "full scrollbar size".

The given callback will be queried for the count instead of the data provider DataProvider.size(Query) method when the component has a distinct data provider set with HasLazyDataView.setItems(BackEndDataProvider).

Parameters:

callback - the callback to use for determining item count in the backend, not null

See Also:

• setItemCountFromDataProvider()
• setItemCountUnknown()

setItemCountFromDataProvider

public void setItemCountFromDataProvider()

Switches the component to get the exact item count from the data provider's DataProvider.size(Query). Use this when it is cheap to get the exact item count and it is desired that the user sees the "full scrollbar size".

Calling this method will clear any previously set count callback with the setItemCountCallback(CallbackDataProvider.CountCallback) method.

Specified by:

setItemCountFromDataProvider in interface LazyDataView<T>

Overrides:

setItemCountFromDataProvider in class AbstractLazyDataView<T>

setItemCountEstimate

public void setItemCountEstimate(int itemCountEstimate)

Sets the estimated item count for the component. The component will automatically fetch more items once the estimate is reached or adjust the count if the backend runs out of items before the end. Use this when the backend will have a lot more items than shown by default and it should be shown to the user.

The given estimate is discarded if it is less than the currently shown range or if the actual number of items has been determined. The estimate shouldn't be less than two pages (see setPageSize(int) in the component) or it causes unnecessary backend requests.

Calling this method will clear any previously set count callback setItemCountCallback(CallbackDataProvider.CountCallback).

Specified by:

setItemCountEstimate in interface LazyDataView<T>

Overrides:

setItemCountEstimate in class AbstractLazyDataView<T>

Parameters:

itemCountEstimate - estimated item count of the backend

See Also:

• LazyDataView.setItemCountUnknown()
• LazyDataView.setItemCountEstimateIncrease(int)

setItemCountUnknown

public void setItemCountUnknown()

Switches the component to automatically extend the number of items as the previous end is almost reached. The component stops increasing the number of items once the backend has run out of items. Not getting the exact size of the backend upfront can improve performance with large sets of data.

The default initial item count and how much the item count is increased depends on the component. These values can be customized with LazyDataView.setItemCountEstimate(int) and LazyDataView.setItemCountEstimateIncrease(int) when the backend has a lot of items and faster scrolling down is desired.

Calling this method will clear any previously set count callback setItemCountCallback(CallbackDataProvider.CountCallback).

Specified by:

setItemCountUnknown in interface LazyDataView<T>

Overrides:

setItemCountUnknown in class AbstractLazyDataView<T>