Java tutorial
/* * Copyright (c) 2010, 2017, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package javafx.scene.control; import javafx.scene.control.skin.LabelSkin; import com.sun.javafx.scene.NodeHelper; import javafx.beans.property.ObjectProperty; import javafx.beans.property.ObjectPropertyBase; import javafx.beans.value.ChangeListener; import javafx.beans.value.WritableValue; import javafx.css.StyleableProperty; import javafx.scene.AccessibleRole; import javafx.scene.Node; /** * Label is a non-editable text control. A Label is useful for displaying * text that is required to fit within a specific space, and thus may need * to use an ellipsis or truncation to size the string to fit. Labels also are * useful in that they can have mnemonics which, if used, will send focus to * the Control listed as the target of the <code>labelFor</code> property. * <p> * Label sets focusTraversable to false. * </p> * * <p>Example: * <pre><code>Label label = new Label("a label");</code></pre> * @since JavaFX 2.0 */ public class Label extends Labeled { /*************************************************************************** * * * Constructors * * * **************************************************************************/ /** * Creates an empty label */ public Label() { initialize(); } /** * Creates Label with supplied text. * @param text null text is treated as the empty string */ public Label(String text) { super(text); initialize(); } /** * Creates a Label with the supplied text and graphic. * @param text null text is treated as the empty string * @param graphic a null graphic is acceptable */ public Label(String text, Node graphic) { super(text, graphic); initialize(); } private void initialize() { getStyleClass().setAll("label"); setAccessibleRole(AccessibleRole.TEXT); // Labels are not focus traversable, unlike most other UI Controls. // focusTraversable is styleable through css. Calling setFocusTraversable // makes it look to css like the user set the value and css will not // override. Initializing focusTraversable by calling set on the // CssMetaData ensures that css will be able to override the value. ((StyleableProperty<Boolean>) (WritableValue<Boolean>) focusTraversableProperty()).applyStyle(null, Boolean.FALSE); } /*************************************************************************** * * * Properties * * * **************************************************************************/ private ChangeListener<Boolean> mnemonicStateListener = (observable, oldValue, newValue) -> { NodeHelper.showMnemonicsProperty(Label.this).setValue(newValue); }; /** * A Label can act as a label for a different Control or * Node. This is used for Mnemonics and Accelerator parsing. * This allows setting of the target Node. * @return the Node that this label is to be associated with */ public ObjectProperty<Node> labelForProperty() { if (labelFor == null) { labelFor = new ObjectPropertyBase<Node>() { Node oldValue = null; @Override protected void invalidated() { if (oldValue != null) { NodeHelper.getNodeAccessor().setLabeledBy(oldValue, null); NodeHelper.showMnemonicsProperty(oldValue).removeListener(mnemonicStateListener); } final Node node = get(); if (node != null) { NodeHelper.getNodeAccessor().setLabeledBy(node, Label.this); NodeHelper.showMnemonicsProperty(node).addListener(mnemonicStateListener); NodeHelper.setShowMnemonics(Label.this, NodeHelper.isShowMnemonics(node)); } else { NodeHelper.setShowMnemonics(Label.this, false); } oldValue = node; } @Override public Object getBean() { return Label.this; } @Override public String getName() { return "labelFor"; } }; } return labelFor; } private ObjectProperty<Node> labelFor; public final void setLabelFor(Node value) { labelForProperty().setValue(value); } public final Node getLabelFor() { return labelFor == null ? null : labelFor.getValue(); } /*************************************************************************** * * * Methods * * * **************************************************************************/ /** {@inheritDoc} */ @Override protected Skin<?> createDefaultSkin() { return new LabelSkin(this); } /*************************************************************************** * * * CSS Support * * * **************************************************************************/ /** * Returns the initial focus traversable state of this control, for use * by the JavaFX CSS engine to correctly set its initial value. This method * is overridden as by default UI controls have focus traversable set to true, * but that is not appropriate for this control. * * @since 9 */ @Override protected Boolean getInitialFocusTraversable() { return Boolean.FALSE; } }