com.google.gwt.view.client

Class ListDataProvider<T>

java.lang.Object

com.google.gwt.view.client.AbstractDataProvider<T>

com.google.gwt.view.client.ListDataProvider<T>

Type Parameters:

T - the data type of the list

All Implemented Interfaces:

ProvidesKey<T>

public class ListDataProvider<T>
extends AbstractDataProvider<T>

A concrete subclass of AbstractDataProvider that is backed by an in-memory list.

Modifications (inserts, removes, sets, etc.) to the list returned by getList() will be reflected in the model. However, mutations to the items contained within the list will NOT be reflected in the model. You must call List.set(int, Object) to update the item within the list and push the change to the display, or call refresh() to push all rows to the displays. List.set(int, Object) performs better because it allows the data provider to push only those rows which have changed, and usually allows the display to re-render only a subset of the rows.

Example

public class ListDataProviderExample implements EntryPoint {

  public void onModuleLoad() {
    // Create a CellList.
    CellList<String> cellList = new CellList<String>(new TextCell());

    // Create a list data provider.
    final ListDataProvider<String> dataProvider = new ListDataProvider<String>();

    // Add the cellList to the dataProvider.
    dataProvider.addDataDisplay(cellList);

    // Create a form to add values to the data provider.
    final TextBox valueBox = new TextBox();
    valueBox.setText("Enter new value");
    Button addButton = new Button("Add value", new ClickHandler() {
      public void onClick(ClickEvent event) {
        // Get the value from the text box.
        String newValue = valueBox.getText();

        // Get the underlying list from data dataProvider.
        List<String> list = dataProvider.getList();

        // Add the value to the list. The dataProvider will update the cellList.
        list.add(newValue);
      }
    });

    // Add the widgets to the root panel.
    VerticalPanel vPanel = new VerticalPanel();
    vPanel.add(valueBox);
    vPanel.add(addButton);
    vPanel.add(cellList);
    RootPanel.get().add(vPanel);
  }
}

Constructor Summary

Constructors

Constructor and Description
ListDataProvider() Creates an empty model.
ListDataProvider(java.util.List<T> listToWrap) Creates a list model that wraps the given list.
ListDataProvider(java.util.List<T> listToWrap, ProvidesKey<T> keyProvider) Creates a list model that wraps the given list.
ListDataProvider(ProvidesKey<T> keyProvider) Creates an empty list model that wraps the given collection.

Method Summary

Modifier and Type	Method and Description
void	flush() Flush pending list changes to the displays.
java.util.List<T>	getList() Get the list that backs this model.
protected void	onRangeChanged(HasData<T> display) Called when a display changes its range of interest.
void	refresh() Refresh all of the displays listening to this adapter.
void	setList(java.util.List<T> listToWrap) Replace this model's list with the specified list.

Methods inherited from class com.google.gwt.view.client.AbstractDataProvider

addDataDisplay, getDataDisplays, getKey, getKeyProvider, getRanges, removeDataDisplay, updateRowCount, updateRowData, updateRowData

Methods inherited from class java.lang.Object

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

Constructor Detail

ListDataProvider

public ListDataProvider()

Creates an empty model.

ListDataProvider

public ListDataProvider(java.util.List<T> listToWrap)

Creates a list model that wraps the given list.

The wrapped list should no longer be modified as the data provider cannot detect changes to the wrapped list. Instead, call getList() to retrieve a wrapper that can be modified and will correctly forward changes to displays.

Parameters:

listToWrap - the List to be wrapped

ListDataProvider

public ListDataProvider(ProvidesKey<T> keyProvider)

Creates an empty list model that wraps the given collection.

Parameters:

keyProvider - an instance of ProvidesKey, or null if the record object should act as its own key

ListDataProvider

public ListDataProvider(java.util.List<T> listToWrap,
                        ProvidesKey<T> keyProvider)

Creates a list model that wraps the given list.

The wrapped list should no longer be modified as the data provider cannot detect changes to the wrapped list. Instead, call getList() to retrieve a wrapper that can be modified and will correctly forward changes to displays.

Parameters:

listToWrap - the List to be wrapped

keyProvider - an instance of ProvidesKey, or null if the record object should act as its own key

Method Detail

flush

public void flush()

Flush pending list changes to the displays. By default, displays are informed of modifications to the underlying list at the end of the current event loop, which makes it possible to perform multiple operations synchronously without repeatedly refreshing the displays. This method can be called to flush the changes immediately instead of waiting until the end of the current event loop.

getList

public java.util.List<T> getList()

Get the list that backs this model. Changes to the list will be reflected in the model.

NOTE: Mutations to the items contained within the list will NOT be reflected in the model. You must call List.set(int, Object) to update the item within the list and push the change to the display, or call refresh() to push all rows to the displays. List.set(int, Object) performs better because it allows the data provider to push only those rows which have changed, and usually allows the display to re-render only a subset of the rows.

Returns:

the list

See Also:

setList(List)

refresh

public void refresh()

Refresh all of the displays listening to this adapter.

Use refresh() to push mutations to the underlying data items contained within the list. The data provider cannot detect changes to data objects within the list, so you must call this method if you modify items.

This is a shortcut for calling List.set(int, Object) on every item that you modify, but note that calling List.set(int, Object) performs better because the data provider knows which rows were modified and can push only the modified rows the displays.

setList

public void setList(java.util.List<T> listToWrap)

Replace this model's list with the specified list.

The wrapped list should no longer be modified as the data provider cannot detect changes to the wrapped list. Instead, call getList() to retrieve a wrapper that can be modified and will correctly forward changes to displays.

Parameters:

listToWrap - the model's new list

See Also:

getList()

onRangeChanged

protected void onRangeChanged(HasData<T> display)

Description copied from class: AbstractDataProvider

Called when a display changes its range of interest.

Specified by:

onRangeChanged in class AbstractDataProvider<T>

Parameters:

display - the display whose range has changed