How to Use Labels如何使用标签

With the JLabel class, you can display unselectable text and images. 使用JLabel类，可以显示不可选择的文本和图像。If you need to create a component that displays a string, an image, or both, you can do so by using or extending JLabel. 如果需要创建一个显示字符串、图像或两者的组件，可以使用或扩展JLabel。If the component is interactive and has a certain state, use a button instead of a label.如果组件是交互式的并且具有特定状态，则使用按钮而不是标签。

By specifying HTML code in a label's text, you can give the label various characteristics such as multiple lines, multiple fonts or multiple colors. 通过在标签的文本中指定HTML代码，可以为标签提供各种特性，如多行、多字体或多种颜色。If the label uses just a single color or font, you can avoid the overhead of HTML processing by using the setForeground or setFont method instead. 如果标签仅使用单一颜色或字体，则可以使用setForeground或setFont方法来避免HTML处理的开销。See Using HTML in Swing Components for details.有关详细信息，请参阅在Swing组件中使用HTML。

Note that labels are not opaque by default. 请注意，默认情况下标签不是不透明的。If you need to paint the label's background, it is recommended that you turn its opacity property to "true". 如果需要绘制标签的背景，建议将其不透明度属性设置为“true”。The following code snippet shows how to do this.下面的代码片段显示了如何做到这一点。

label.setOpaque(true);

The following picture introduces an application that displays three labels. 下图介绍了一个显示三个标签的应用程序。The window is divided into three rows of equal height; the label in each row is as wide as possible.窗口分为三行，高度相等；每行中的标签尽可能宽。

Below is the code from LabelDemo.java that creates the labels in the previous example.下面是LabelDemo.java中的代码，用于创建前面示例中的标签。

ImageIcon icon = createImageIcon("images/middle.gif");
. . .
label1 = new JLabel("Image and Text",
                    icon,
                    JLabel.CENTER);
//Set the position of the text, relative to the icon:
label1.setVerticalTextPosition(JLabel.BOTTOM);
label1.setHorizontalTextPosition(JLabel.CENTER);

label2 = new JLabel("Text-Only Label");
label3 = new JLabel(icon);

The code for the createImageIcon method is similar to that used throughout this tutorial. createImageIcon方法的代码与本教程中使用的代码类似。You can find it in How to Use Icons.您可以在如何使用图标中找到它。

Often, a label describes another component. 通常，标签描述另一个组件。When this occurs, you can improve your program's accessibility by using the setLabelFor method to identify the component that the label describes. 发生这种情况时，可以通过使用setLabelFor方法来标识标签描述的组件，从而提高程序的可访问性。For example:例如：

amountLabel.setLabelFor(amountField);

The preceding code, taken from the FormattedTextFieldDemo example discussed in How to Use Formatted Text Fields, lets assistive technologies know that the label (amountLabel) provides information about the formatted text field (amountField). 前面的代码取自如何使用格式化文本字段中讨论的FormattedTextFieldDemo示例，它让辅助技术知道标签（amountLabel）提供了有关格式化文本字段（amountField）的信息。For more information about assistive technologies, see How to Support Assistive Technologies.有关辅助技术的更多信息，请参阅如何支持辅助技术。

The Label API

The following tables list the commonly used JLabel constructors and methods. 下表列出了常用的JLabel构造函数和方法。Other methods you are likely to call are defined by the Component and JComponent classes. 您可能调用的其他方法由Component和JComponent类定义。They include setFont, setForeground, setBorder, setOpaque, and setBackground. 它们包括setFont、setForeground、setBorder、setOpaque和setBackground。See The JComponent Class for details. 有关详细信息，请参阅JComponent类。The API for using labels falls into three categories:使用标签的API分为三类：

• Setting or Getting the Label's Contents设置或获取标签内容
• Fine Tuning the Label's Appearance微调标签的外观
• Supporting Accessibility支持无障碍

Examples That Use Labels使用标签的示例

The following table lists some of the many examples that use labels.下表列出了许多使用标签的示例。

See the Using JavaFX UI Controls: Label tutorial to learn about JavaFX labeled controls.请参阅使用JavaFXUI控件：标签教程以了解JavaFX标签控件。