com.google.gwt.view.client.DefaultSelectionModel 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.view.client.MultiSelectionModel.SelectionChange;
import com.google.gwt.view.client.SelectionModel.AbstractSelectionModel;
import java.util.HashMap;
import java.util.Map;
/**
* A convenience {@link SelectionModel} that allows items to be selected
* according to a subclass-defined rule, plus a list of positive or negative
* exceptions.
*
* @param the data type of records in the list
*/
public abstract class DefaultSelectionModel extends AbstractSelectionModel {
private final Map exceptions = new HashMap();
/**
* A map of keys to the item and its pending selection state.
*/
private final Map> selectionChanges =
new HashMap>();
/**
* Constructs a DefaultSelectionModel without a key provider.
*/
public DefaultSelectionModel() {
super(null);
}
/**
* Constructs a DefaultSelectionModel with the given key provider.
*
* @param keyProvider an instance of ProvidesKey, or null if the item
* should act as its own key
*/
public DefaultSelectionModel(ProvidesKey keyProvider) {
super(keyProvider);
}
/**
* Removes all exceptions.
*/
public void clearExceptions() {
exceptions.clear();
selectionChanges.clear();
scheduleSelectionChangeEvent();
}
/**
* Returns true if the given item should be selected by default. Subclasses
* implement this method in order to define the default selection behavior.
*
* @param item an object of this {@link SelectionModel}'s type
* @return true if the item should be selected by default
*/
public abstract boolean isDefaultSelected(T item);
/**
* If the given item is marked as an exception, return the exception value.
* Otherwise, return the value of isDefaultSelected for the given item.
*/
@Override
public boolean isSelected(T item) {
resolveChanges();
// Check exceptions first
Object key = getKey(item);
Boolean exception = exceptions.get(key);
if (exception != null) {
return exception.booleanValue();
}
// If not in exceptions, return the default
return isDefaultSelected(item);
}
/**
* Sets an item's selection state. If the item is currently marked as an
* exception, and the new selected state differs from the previous selected
* state, the object is removed from the list of exceptions. Otherwise, the
* object is added to the list of exceptions with the given selected state.
*/
@Override
public void setSelected(T item, boolean selected) {
selectionChanges.put(getKey(item), new SelectionChange(item, selected));
scheduleSelectionChangeEvent();
}
@Override
protected void fireSelectionChangeEvent() {
if (isEventScheduled()) {
setEventCancelled(true);
}
resolveChanges();
}
/**
* Copies the exceptions map into a user-supplied map.
*
* @param output the user supplied map
* @return the user supplied map
*/
protected Map getExceptions(Map output) {
output.clear();
output.putAll(exceptions);
return output;
}
private void resolveChanges() {
boolean changed = false;
for (Map.Entry> entry : selectionChanges.entrySet()) {
Object key = entry.getKey();
SelectionChange value = entry.getValue();
T item = value.getItem();
boolean selected = value.isSelected();
boolean defaultSelected = isDefaultSelected(item);
Boolean previousException = exceptions.get(key);
if (defaultSelected == selected) {
// Not an exception, remove from exceptions table if present
if (previousException != null) {
exceptions.remove(key);
changed = true;
}
} else {
// Add as an exception if not already there
if (previousException != Boolean.valueOf(selected)) {
exceptions.put(key, selected);
changed = true;
}
}
}
selectionChanges.clear();
// Fire a selection change event.
if (changed) {
SelectionChangeEvent.fire(this);
}
}
}