com.google.gwt.view.client.SelectionModel Maven / Gradle / Ivy
/*
* Copyright 2010 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package com.google.gwt.view.client;
import com.google.gwt.core.client.Scheduler;
import com.google.gwt.core.client.Scheduler.ScheduledCommand;
import com.google.gwt.event.shared.GwtEvent;
import com.google.gwt.event.shared.HandlerManager;
import com.google.gwt.event.shared.HandlerRegistration;
import com.google.gwt.view.client.SelectionChangeEvent.HasSelectionChangedHandlers;
/**
* A model for selection within a list.
*
* @param the data type of records in the list
*/
public interface SelectionModel extends HasSelectionChangedHandlers, ProvidesKey {
/**
* A default implementation of {@link SelectionModel} that provides listener
* addition and removal.
*
* @param the data type of records in the list
*/
public abstract class AbstractSelectionModel implements SelectionModel {
private final HandlerManager handlerManager = new HandlerManager(this);
/**
* Set to true if the next scheduled event should be canceled.
*/
private boolean isEventCancelled;
/**
* Set to true if an event is scheduled to be fired.
*/
private boolean isEventScheduled;
private final ProvidesKey keyProvider;
/**
* Construct an AbstractSelectionModel with a given key provider.
*
* @param keyProvider an instance of ProvidesKey, or null if the record
* object should act as its own key
*/
protected AbstractSelectionModel(ProvidesKey keyProvider) {
this.keyProvider = keyProvider;
}
@Override
public HandlerRegistration addSelectionChangeHandler(
SelectionChangeEvent.Handler handler) {
return handlerManager.addHandler(SelectionChangeEvent.getType(), handler);
}
@Override
public void fireEvent(GwtEvent event) {
handlerManager.fireEvent(event);
}
@Override
public Object getKey(T item) {
return (keyProvider == null || item == null) ? item
: keyProvider.getKey(item);
}
/**
* Returns a {@link ProvidesKey} instance that simply returns the input data
* item.
*
* @return the key provider, which may be null
*/
public ProvidesKey getKeyProvider() {
return keyProvider;
}
/**
* Fire a {@link SelectionChangeEvent}. Multiple firings may be coalesced.
*/
protected void fireSelectionChangeEvent() {
if (isEventScheduled()) {
setEventCancelled(true);
}
SelectionChangeEvent.fire(AbstractSelectionModel.this);
}
/**
* Return true if the next scheduled event should be canceled.
*
* @return true if the event is canceled
*/
protected boolean isEventCancelled() {
return isEventCancelled;
}
/**
* Return true if an event is scheduled to be fired.
*
* @return true if the event is scheduled
*/
protected boolean isEventScheduled() {
return isEventScheduled;
}
/**
* Schedules a {@link SelectionChangeEvent} to fire at the
* end of the current event loop.
*/
protected void scheduleSelectionChangeEvent() {
setEventCancelled(false);
if (!isEventScheduled()) {
setEventScheduled(true);
Scheduler.get().scheduleFinally(new ScheduledCommand() {
public void execute() {
setEventScheduled(false);
if (isEventCancelled()) {
setEventCancelled(false);
return;
}
fireSelectionChangeEvent();
}
});
}
}
/**
* Set whether the next scheduled event should be canceled.
*
* @param isEventCancelled if true, cancel the event
*/
protected void setEventCancelled(boolean isEventCancelled) {
this.isEventCancelled = isEventCancelled;
}
/**
* Set whether an event is scheduled to be fired.
*
* @param isEventScheduled if true, schedule the event
*/
protected void setEventScheduled(boolean isEventScheduled) {
this.isEventScheduled = isEventScheduled;
}
}
/**
* Adds a {@link SelectionChangeEvent} handler.
*
* @param handler the handler
* @return the registration for the event
*/
@Override
HandlerRegistration addSelectionChangeHandler(SelectionChangeEvent.Handler handler);
/**
* Check if an object is selected.
*
* @param object the object
* @return true if selected, false if not
*/
boolean isSelected(T object);
/**
* Set the selected state of an object and fire a
* {@link SelectionChangeEvent} if the selection has
* changed. Subclasses should not fire an event in the case where
* selected is true and the object was already selected, or selected
* is false and the object was not previously selected.
*
* @param object the object to select or deselect
* @param selected true to select, false to deselect
*/
void setSelected(T object, boolean selected);
}