com.vaadin.flow.component.listbox.ListBox Maven / Gradle / Ivy
/*
* Copyright 2000-2024 Vaadin Ltd.
*
* 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.vaadin.flow.component.listbox;
import java.util.List;
import java.util.Objects;
import java.util.stream.IntStream;
import com.vaadin.flow.data.selection.SingleSelect;
/**
* List Box allows the user to select one or more values from a scrollable list
* of items. Although its functionally similar to Checkbox Group and Radio
* Button Group, List Box is designed to be used as a lightweight scrollable
* selection list rather than a form input field.
*
* List Box also supports using dividers to group related items. Use them
* sparingly to avoid creating unnecessary visual clutter. List Box supports
* both single and multiple selection. The former allows the user to select only
* one item while the latter enables multiple items to be selected.
*
* Items can be rendered with rich content instead of plain text. This can be
* useful to provide additional information in a more legible fashion than
* appending it to the item text.
*
* Best Practices:
* List Box is not designed to be used as an input field in forms, and lacks
* features like label, helper, and validation errors. List Box is best suited
* to be used as a lightweight, scrollable, single-column list for single or
* multi-selection of items.
*
* @author Vaadin Ltd
*
* @param
* the type of the items contained by this component
* @see MultiSelectListBox
*/
public class ListBox extends ListBoxBase, T, T>
implements SingleSelect, T> {
/**
* Creates a new list box component.
*/
public ListBox() {
super("selected", Integer.class, null, ListBox::presentationToModel,
ListBox::modelToPresentation);
}
private static T presentationToModel(ListBox listBox,
Integer selectedIndex) {
if (selectedIndex == null || selectedIndex.intValue() == -1) {
return null;
}
return listBox.getItemComponents().get(selectedIndex.intValue())
.getItem();
}
private static Integer modelToPresentation(ListBox listBox,
T selectedItem) {
if (selectedItem == null) {
return -1;
}
List> itemComponents = listBox.getItemComponents();
return IntStream.range(0, itemComponents.size())
.filter(idx -> listBox.getItemId(selectedItem).equals(
listBox.getItemId(itemComponents.get(idx).getItem())))
.findFirst().orElseThrow(() -> new IllegalArgumentException(
"Could not find given value from the item set"));
}
/**
* Compares two value instances to each other to determine whether they are
* equal. Equality is used to determine whether to update internal state and
* fire an event when {@link #setValue(Object)} or
* {@link #setModelValue(Object, boolean)} is called. Subclasses can
* override this method to define an alternative comparison method instead
* of {@link Objects#equals(Object)}.
*
* @param value1
* the first instance
* @param value2
* the second instance
* @return true if the instances are equal; otherwise
* false
*/
@Override
protected boolean valueEquals(T value1, T value2) {
if (value1 == null && value2 == null)
return true;
if (value1 == null || value2 == null)
return false;
return getItemId(value1).equals(getItemId(value2));
}
}