com.google.gwt.user.client.ui.ValueLabel.java Source code

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Here is the source code for com.google.gwt.user.client.ui.ValueLabel.java

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/*
 * 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.user.client.ui;

import com.google.gwt.dom.client.Document;
import com.google.gwt.dom.client.Element;
import com.google.gwt.editor.client.IsEditor;
import com.google.gwt.editor.client.LeafValueEditor;
import com.google.gwt.editor.client.adapters.TakesValueEditor;
import com.google.gwt.text.shared.Parser;
import com.google.gwt.text.shared.Renderer;
import com.google.gwt.uibinder.client.UiConstructor;
import com.google.gwt.user.client.TakesValue;

import java.text.ParseException;

/**
 * A label displaying its value through a renderer.
 * 
 * @param <T> the value type.
 */
public class ValueLabel<T> extends LabelBase<T> implements TakesValue<T>, IsEditor<LeafValueEditor<T>> {

    /**
     * Creates a ValueLabel widget that wraps an existing &lt;span&gt; element.
     * <p>
     * The ValueLabel's value will be <code>null</code>, whether the element being
     * wrapped has content or not. Use {@link #wrap(Element, Renderer, Parser)} to
     * parse the initial element's content to initialize the ValueLabel's value.
     * <p>
     * This element must already be attached to the document. If the element is
     * removed from the document, you must call
     * {@link RootPanel#detachNow(Widget)}.
     * 
     * @param element the element to be wrapped
     * @param renderer the renderer used to render values into the element
     */
    public static <T> ValueLabel<T> wrap(Element element, Renderer<? super T> renderer) {
        // Assert that the element is attached.
        assert Document.get().getBody().isOrHasChild(element);

        ValueLabel<T> label = new ValueLabel<T>(element, renderer);

        // Mark it attached and remember it for cleanup.
        label.onAttach();
        RootPanel.detachOnWindowClose(label);

        return label;
    }

    /**
     * Creates a ValueLabel widget that wraps an existing &lt;span&gt; element.
     * <p>
     * The ValueLabel's value will be initialized with the element's content,
     * passed through the <code>parser</code>.
     * <p>
     * This element must already be attached to the document. If the element is
     * removed from the document, you must call
     * {@link RootPanel#detachNow(Widget)}.
     * 
     * @param element the element to be wrapped
     * @param renderer the renderer used to render values into the element
     * @param parser the parser used to initialize the ValueLabel's value from the
     *          element's content
     */
    public static <T> ValueLabel<T> wrap(Element element, Renderer<? super T> renderer, Parser<? extends T> parser)
            throws ParseException {
        ValueLabel<T> label = wrap(element, renderer);

        label.setValue(parser.parse(element.getInnerText()));

        // Mark it attached and remember it for cleanup.
        label.onAttach();
        RootPanel.detachOnWindowClose(label);

        return label;
    }

    private final Renderer<? super T> renderer;
    private T value;
    private LeafValueEditor<T> editor;

    /**
     * Creates an empty value label.
     * 
     * @param renderer
     */
    @UiConstructor
    public ValueLabel(Renderer<? super T> renderer) {
        super(true);
        this.renderer = renderer;
    }

    /**
     * This constructor may be used by subclasses to explicitly use an existing
     * element. This element must be either a &lt;span&gt; or a &lt;div&gt;
     * element.
     * 
     * @param element the element to be used
     */
    protected ValueLabel(Element element, Renderer<? super T> renderer) {
        super(element);
        this.renderer = renderer;
    }

    public LeafValueEditor<T> asEditor() {
        if (editor == null) {
            editor = TakesValueEditor.of(this);
        }
        return editor;
    }

    public T getValue() {
        return value;
    }

    public void setValue(T value) {
        this.value = value;
        directionalTextHelper.setTextOrHtml(renderer.render(value), false);
        updateHorizontalAlignment();
    }
}