Swing JLabel

JLabel類可以顯示文本，圖像，或兩者兼而有。標籤的內容是一致的，通過設置在其顯示區域中的垂直和水平位置。默認情況下，標籤在其顯示區域垂直居中。純文字標籤的前沿對齊，默認情況下，圖像標籤，默認情況下，水平居中。

類聲明

以下是聲明的javax.swing.JLabel類：

public class JLabel extends JComponent implements SwingConstants, Accessible

字段域

以下是javax.swing.JLabel類的字段：

• protected Component labelFor

類構造函數

S.N.

構造函數 & 描述

1

JLabel()
Creates a JLabel instance with no image and with an empty string for the title.

2

JLabel(Icon image)
Creates a JLabel instance with the specified image.

3

JLabel(Icon image, int horizontalAlignment)
Creates a JLabel instance with the specified image and horizontal alignment.

4

JLabel(String text)
Creates a JLabel instance with the specified text.

5

JLabel(String text, Icon icon, int horizontalAlignment)
Creates a JLabel instance with the specified text, image, and horizontal alignment.

6

JLabel(String text, int horizontalAlignment)
Creates a JLabel instance with the specified text and horizontal alignment.

類方法

S.N.

方法 & 描述

1

protected int checkHorizontalKey(int key, String message)
Verify that key is a legal value for the horizontalAlignment properties.

2

protected int checkVerticalKey(int key, String message)
Verify that key is a legal value for the verticalAlignment or verticalTextPosition properties.

3

AccessibleContext getAccessibleContext()
Get the AccessibleContext of this object.

4

Icon getDisabledIcon()
Returns the icon used by the label when it's disabled.

5

int getDisplayedMnemonic()
Return the keycode that indicates a mnemonic key.

6

int getDisplayedMnemonicIndex()
Returns the character, as an index, that the look and feel should provide decoration for as representing the mnemonic character.

7

int getHorizontalAlignment()
Returns the alignment of the label's contents along the X axis.

8

int getHorizontalTextPosition()
Returns the horizontal position of the label's text, relative to its image.

9

Icon getIcon()
Returns the graphic image (glyph, icon) that the label displays.

10

int getIconTextGap()
Returns the amount of space between the text and the icon displayed in this label.

11

Component getLabelFor()
Get the component this is labelling.

12

String getText()
Returns the text string that the label displays.

13

LabelUI getUI()
Returns the L&F object that renders this component.

14

String getUIClassID()
Returns a string that specifies the name of the l&f class that renders this component.

15

int getVerticalAlignment()
Returns the alignment of the label's contents along the Y axis.

16

int getVerticalTextPosition()
Returns the vertical position of the label's text, relative to its image.

17

boolean imageUpdate(Image img, int infoflags, int x, int y, int w, int h)
This is overridden to return false if the current Icon's Image is not equal to the passed in Image img.

18

protected String paramString()
Returns a string representation of this JLabel.

19

void setDisabledIcon(Icon disabledIcon)
Set the icon to be displayed if this JLabel is "disabled" (JLabel.setEnabled(false)).

20

void setDisplayedMnemonic(char aChar)
Specifies the displayedMnemonic as a char value.

21

void setDisplayedMnemonic(int key)
Specify a keycode that indicates a mnemonic key.

22

void setDisplayedMnemonicIndex(int index)
Provides a hint to the look and feel as to which character in the text should be decorated to represent the mnemonic.

23

void setHorizontalAlignment(int alignment)
Sets the alignment of the label's contents along the X axis.

24

void setHorizontalTextPosition(int textPosition)
Sets the horizontal position of the label's text, relative to its image.

25

void setIcon(Icon icon)
Defines the icon this component will display.

26

void setIconTextGap(int iconTextGap)
If both the icon and text properties are set, this property defines the space between them.

27

void setLabelFor(Component c)
Set the component this is labelling.

28

void setText(String text)
Defines the single line of text this component will display.

29

void setUI(LabelUI ui)
Sets the L&F object that renders this component.

30

void setVerticalAlignment(int alignment)
Sets the alignment of the label's contents along the Y axis.

31

void setVerticalTextPosition(int textPosition)
Sets the vertical position of the label's text, relative to its image.

32

void updateUI()
Resets the UI property to a value from the current look and feel.

方法繼承

這個類從以下類繼承的方法：

• javax.swing.JComponent

• java.awt.Container

• java.awt.Component

• java.lang.Object

JLabel 例子

選擇使用任何編輯器創建以下java程序在 D:/ > SWING > com > yiibai > gui >

SwingControlDemo.java

package com.yiibai.gui; import java.awt.*; import java.awt.event.*; import javax.swing.*; public class SwingControlDemo { private JFrame mainFrame; private JLabel headerLabel; private JLabel statusLabel; private JPanel controlPanel; public SwingControlDemo(){ prepareGUI(); } public static void main(String[] args){ SwingControlDemo swingControlDemo = new SwingControlDemo(); swingControlDemo.showLabelDemo(); } private void prepareGUI(){ mainFrame = new JFrame("Java Swing Examples"); mainFrame.setSize(400,400); mainFrame.setLayout(new GridLayout(3, 1)); mainFrame.addWindowListener(new WindowAdapter() { public void windowClosing(WindowEvent windowEvent){ System.exit(0); } }); headerLabel = new JLabel("", JLabel.CENTER); statusLabel = new JLabel("",JLabel.CENTER); statusLabel.setSize(350,100); controlPanel = new JPanel(); controlPanel.setLayout(new FlowLayout()); mainFrame.add(headerLabel); mainFrame.add(controlPanel); mainFrame.add(statusLabel); mainFrame.setVisible(true); } private void showLabelDemo(){ headerLabel.setText("Control in action: JLabel"); JLabel label = new JLabel("", JLabel.CENTER); label.setText("Welcome to TutorialsPoint Swing Tutorial."); label.setOpaque(true); label.setBackground(Color.GRAY); label.setForeground(Color.WHITE); controlPanel.add(label); mainFrame.setVisible(true); } }

編譯程序，使用命令提示符。進入到 D:/ > SWING ，然後鍵入以下命令。

D:SWING>javac comyiibaiguiSwingControlDemo.java

如果沒有錯誤出現，這意味着編譯成功。使用下面的命令來運行程序。

D:SWING>java com.yiibai.gui.SwingControlDemo

驗證下面的輸出