《Java 二图形设计卷Ⅱ- SWING》第8章标签与按钮

《Java 2 图形设计卷Ⅱ- SWING》第8章标签与按钮

第8章标签与按钮

　　Swing的标签和按钮分别用JLabel和JButton类表示，它们是能够显示文本或图标的简单组件。缺省时，标签没有边框，可以显示一个字符串，一个图标或同时显示字符串和图标。除了用于修饰文本域等不重要的小事情外，Swing的标签还能起到图像画布(显示一个图像的组件)的作用。由于AWT的图像不是组件，不能把它们添加到一个容器中。因此，使用AWT的开发人员实现了各种不同的图像画布类；然而，在Swing中，可以把JLabel类当作图像画面使用(注：有关图像画面的更多信息参见4.3.1“Swing组件中的定制绘制”一节)。
　　按钮大概是使用最为普遍的用户界面组件。按钮通常带有某种边框，且可以被鼠标或快捷键激活。Swing按钮比Swing标签要复杂得多，不仅因为能够激活它们来完成某个功能，而且很多其他Swing组件都是AbstractButton类的扩展，而AbstractButton类是Swing按钮的基类。

8.1 JLabel与JBution

8.2 JLabel

例8-1 运行中的JLabel

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

public class Test extends JApplet {

public Test() {

Container contentPane = getContentPane();

JLabel imageOnly = new JLabel(new ImageIcon(this.getClass().getResource("dogs.gif")));

JLabel textAndImage = new JLabel("Vote!",

new ImageIcon(this.getClass().getResource("ballot_box.gif")),

JLabel.RIGHT);

JScrollPane scrollPane = new JScrollPane(imageOnly);

scrollPane.setPreferredSize(new Dimension(270,200));

contentPane.setLayout(

new FlowLayout(FlowLayout.CENTER, 25, 25));

contentPane.add(textAndImage);

contentPane.add(scrollPane);

}

8.2.1内容排列

例8-2 设置Swing标签的排列属性

import java.net.URL;

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

import javax.swing.border.*;

public class Test extends JApplet implements SwingConstants {

JLabel label = new JLabel("Action!");

JPanel controlPanel = new JPanel();

JComboBox alignmentHorizontal = new JComboBox();

JComboBox alignmentVertical = new JComboBox();

public void init() {

Container contentPane = getContentPane();

ImageIcon icon = new ImageIcon(this.getClass().getResource("slate.gif"));

label.setIcon(icon);

label.setHorizontalAlignment(CENTER);

label.setFont(new Font("Times-Roman", Font.ITALIC, 20));

label.setMaximumSize(new Dimension(0, 150));

setupComboBoxes();

setupControlPanel();

contentPane.setLayout(new BorderLayout());

contentPane.add(controlPanel, "North");

contentPane.add(label, "Center");

alignmentVertical.addItemListener(new ItemListener() {

public void itemStateChanged(ItemEvent event) {

JComboBox b = (JComboBox)event.getSource();

String s = (String)b.getSelectedItem();

int c = getSwingConstantByName(s);

label.setVerticalAlignment(c);

}

});

alignmentHorizontal.addItemListener(new ItemListener() {

public void itemStateChanged(ItemEvent event) {

JComboBox b = (JComboBox)event.getSource();

String s = (String)b.getSelectedItem();

int c = getSwingConstantByName(s);

label.setHorizontalAlignment(c);

}

});

}

void setupComboBoxes() {

alignmentVertical.addItem("Top");

alignmentVertical.addItem("Center");

alignmentVertical.addItem("Bottom");

alignmentHorizontal.addItem("Left");

alignmentHorizontal.addItem("Center");

alignmentHorizontal.addItem("Right");

alignmentVertical.setSelectedItem(

getSwingConstantName(

label.getVerticalAlignment()));

alignmentHorizontal.setSelectedItem(

getSwingConstantName(

label.getHorizontalAlignment()));

}

void setupControlPanel() {

controlPanel.setBorder(

BorderFactory.createTitledBorder("Alignment"));

controlPanel.add(new JLabel(

"Vertical:"));

controlPanel.add(alignmentVertical);

controlPanel.add(Box.createHorizontalStrut(5));

controlPanel.add(Box.createHorizontalStrut(25));

controlPanel.add(new JLabel(

"Horizontal:"));

controlPanel.add(Box.createHorizontalStrut(5));

controlPanel.add(alignmentHorizontal);

}

int getSwingConstantByName(String s) {

if(s.equalsIgnoreCase("left")) return LEFT;

else if(s.equalsIgnoreCase("center")) return CENTER;

else if(s.equalsIgnoreCase("right")) return RIGHT;

else if(s.equalsIgnoreCase("top")) return TOP;

else if(s.equalsIgnoreCase("bottom")) return BOTTOM;

return -1;

}

String getSwingConstantName(int c) {

if(c == LEFT) return "Left";

else if(c == CENTER) return "Center";

else if(c == RIGHT) return "Right";

else if(c == TOP) return "Top";

else if(c == BOTTOM) return "Bottom";

return "undefined";

}

8.2.2文本的位置

例8-3 设置标签的文本位置

import java.net.URL;

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

import javax.swing.border.*;

public class Test extends JApplet implements SwingConstants {

JLabel label = new JLabel("Action!");

JPanel controlPanel = new JPanel();

JComboBox alignmentHorizontal = new JComboBox();

JComboBox alignmentVertical = new JComboBox();

public void init() {

Container contentPane = getContentPane();

ImageIcon icon = new ImageIcon(this.getClass().getResource("penguin.gif"));

label.setIcon(icon);

label.setHorizontalTextPosition(CENTER);

label.setFont(new Font("Times-Roman", Font.ITALIC, 20));

setupComboBoxes();

setupControlPanel();

label.setHorizontalAlignment(JLabel.CENTER);

label.setVerticalAlignment(JLabel.CENTER);

contentPane.setLayout(new BorderLayout());

contentPane.add(controlPanel, "North");

contentPane.add(label, "Center");

alignmentVertical.addItemListener(new ItemListener() {

public void itemStateChanged(ItemEvent event) {

JComboBox b = (JComboBox)event.getSource();

String s = (String)b.getSelectedItem();

int c = getSwingConstantByName(s);

label.setVerticalTextPosition(c);

}

});

alignmentHorizontal.addItemListener(new ItemListener() {

public void itemStateChanged(ItemEvent event) {

JComboBox b = (JComboBox)event.getSource();

String s = (String)b.getSelectedItem();

int c = getSwingConstantByName(s);

label.setHorizontalTextPosition(c);

}

});

}

void setupComboBoxes() {

alignmentVertical.addItem("Top");

alignmentVertical.addItem("Center");

alignmentVertical.addItem("Bottom");

alignmentHorizontal.addItem("Left");

alignmentHorizontal.addItem("Center");

alignmentHorizontal.addItem("Right");

alignmentVertical.setSelectedItem(

getSwingConstantName(

label.getVerticalTextPosition()));

alignmentHorizontal.setSelectedItem(

getSwingConstantName(

label.getHorizontalTextPosition()));

}

void setupControlPanel() {

controlPanel.setBorder(

BorderFactory.createTitledBorder("Text Position"));

controlPanel.add(new JLabel( "Vertical:"));

controlPanel.add(alignmentVertical);

controlPanel.add(Box.createHorizontalStrut(5));

controlPanel.add(Box.createHorizontalStrut(25));

controlPanel.add(new JLabel("Horizontal:"));

controlPanel.add(Box.createHorizontalStrut(5));

controlPanel.add(alignmentHorizontal);

}

int getSwingConstantByName(String s) {

if(s.equalsIgnoreCase("left")) return LEFT;

else if(s.equalsIgnoreCase("center")) return CENTER;

else if(s.equalsIgnoreCase("right")) return RIGHT;

else if(s.equalsIgnoreCase("top")) return TOP;

else if(s.equalsIgnoreCase("bottom")) return BOTTOM;

return -1;

}

String getSwingConstantName(int c) {

if(c == LEFT) return "Left";

else if(c == CENTER) return "Center";

else if(c == RIGHT) return "Right";

else if(c == TOP) return "Top";

else if(c == BOTTOM) return "Bottom";

return "undefined";

}

8.2.3图标/文本间隙

例8-4 设置一个标签的图标/文本间隙

import java.net.URL;

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

import javax.swing.border.*;

public class Test extends JApplet implements SwingConstants {

public void init() {

Container contentPane = getContentPane();

JComboBox iconTextGap = new JComboBox();

JPanel controlPanel = new JPanel();

ImageIcon icon = new ImageIcon(this.getClass().getResource("ladybug.gif"));

final JLabel label = new JLabel("Lady Bug", icon, CENTER);

label.setFont(new Font("Times-Roman", Font.ITALIC, 20));

iconTextGap.addItem("4");

iconTextGap.addItem("10");

iconTextGap.addItem("15");

iconTextGap.addItem("20");

iconTextGap.addItem("25");

controlPanel.add(new JLabel("Icon/Text Gap:"));

controlPanel.add(iconTextGap);

contentPane.setLayout(new BorderLayout());

contentPane.add(controlPanel, "North");

contentPane.add(label, "Center");

iconTextGap.addItemListener(new ItemListener() {

public void itemStateChanged(ItemEvent event) {

JComboBox b = (JComboBox)event.getSource();

String s = (String)b.getSelectedItem();

int gap = Integer.parseInt(s);

label.setIconTextGap(gap);

}

});

}

8.2.4许可状态

例8-5 设置一个标签的许可状态

import java.net.URL;

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

import javax.swing.border.*;

public class Test extends JApplet implements SwingConstants {

public void init() {

Container contentPane = getContentPane();

JComboBox iconTextGap = new JComboBox();

JPanel controlPanel = new JPanel();

ImageIcon icon = new ImageIcon(this.getClass().getResource("ladybug.gif"));

final JLabel label = new JLabel("Lady Bug", icon, CENTER);

label.setFont(new Font("Times-Roman", Font.ITALIC, 20));

iconTextGap.addItem("4");

iconTextGap.addItem("10");

iconTextGap.addItem("15");

iconTextGap.addItem("20");

iconTextGap.addItem("25");

controlPanel.add(new JLabel("Icon/Text Gap:"));

controlPanel.add(iconTextGap);

contentPane.setLayout(new BorderLayout());

contentPane.add(controlPanel, "North");

contentPane.add(label, "Center");

iconTextGap.addItemListener(new ItemListener() {

public void itemStateChanged(ItemEvent event) {

JComboBox b = (JComboBox)event.getSource();

String s = (String)b.getSelectedItem();

int gap = Integer.parseInt(s);

label.setIconTextGap(gap);

}

});

}

8.2.5 JLabel属性

8.2.6 JLabel事件

8.2.7 JLabel类总结

例8-6 创建JLabel实例

import java.net.URL;

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

import javax.swing.border.*;

public class Test extends JApplet implements SwingConstants {

public void init() {

Container contentPane = getContentPane();

JComboBox iconTextGap = new JComboBox();

JPanel controlPanel = new JPanel();

ImageIcon icon = new ImageIcon(this.getClass().getResource("ladybug.gif"));

final JLabel label = new JLabel("Lady Bug", icon, CENTER);

label.setFont(new Font("Times-Roman", Font.ITALIC, 20));

iconTextGap.addItem("4");

iconTextGap.addItem("10");

iconTextGap.addItem("15");

iconTextGap.addItem("20");

iconTextGap.addItem("25");

controlPanel.add(new JLabel("Icon/Text Gap:"));

controlPanel.add(iconTextGap);

contentPane.setLayout(new BorderLayout());

contentPane.add(controlPanel, "North");

contentPane.add(label, "Center");

iconTextGap.addItemListener(new ItemListener() {

public void itemStateChanged(ItemEvent event) {

JComboBox b = (JComboBox)event.getSource();

String s = (String)b.getSelectedItem();

int gap = Integer.parseInt(s);

label.setIconTextGap(gap);

}

});

}

8.3 按钮

8.4 JButtion

例8-7 一个按钮简单例子

import javax.swing.*;

import java.awt.*;

import java.awt.event.*;

import java.util.*;

public class Test extends JApplet {

JButton button = new JButton("button ...",

new ImageIcon(this.getClass().getResource("exclaim.gif")));

int actCnt = 0;

public void init() {

Container contentPane = getContentPane();

contentPane.setLayout(new FlowLayout());

contentPane.add(button);

button.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent event) {

showStatus(event.getActionCommand() +

" activated " + actCnt + " times");

actCnt++;

}

});

}

8.4.1 JButtion属性

8.4.2 JButtion事件

例8-8 处理JButton事件

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

import javax.swing.event.*;

public class Test extends JApplet {

//Icon icon = new ImageIcon("icon.gif");

JButton button = new JButton("button");

public Test() {

Container contentPane = getContentPane();

button.setRolloverIcon(new ImageIcon(this.getClass().getResource("punch.gif")));

button.setIcon(new ImageIcon(this.getClass().getResource("open_hand.gif")));

contentPane.setLayout(new FlowLayout());

contentPane.add(button);

button.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

System.out.println("action!");

}

});

button.addChangeListener(new ChangeListener() {

public void stateChanged(ChangeEvent e) {

System.out.println(getButtonState());

}

});

}

private String getButtonState() {

ButtonModel model = button.getModel();

String state = "Button State: ";

state += model.isSelected() ? "selected" : "deselected";

state += model.isPressed() ? ", pressed" :

", not pressed";

state += model.isArmed() ? ", armed" : ", disarmed";

state += model.isRollover() ? ", rollover" :

", not rollover";

return state;

}

8.4.3 JButtion类总结

例8-9 创建JButton实例

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

public class Test extends JApplet {

Icon icon = new ImageIcon("icon.gif");

JButton noargButton = new JButton(),

textButton = new JButton("text"),

textIconButton = new JButton("text", icon),

iconButton = new JButton(icon);

public Test() {

Container contentPane = getContentPane();

contentPane.setLayout(new FlowLayout());

contentPane.add(noargButton);

contentPane.add(textButton);

contentPane.add(iconButton);

contentPane.add(textIconButton);

}

例8-10 把一个按钮指定为缺省的按钮

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

public class Test extends JApplet {

Icon icon = new ImageIcon("icon.gif");

JButton noargButton = new JButton(),

textButton = new JButton("text"),

textIconButton = new JButton("text", icon),

iconButton = new JButton(icon);

public Test() {

Container contentPane = getContentPane();

contentPane.setLayout(new FlowLayout());

contentPane.add(noargButton);

contentPane.add(textButton);

contentPane.add(iconButton);

contentPane.add(textIconButton);

}

例8-11 程序方式单击一个按钮

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

public class Test extends JApplet {

int clickDuration = 68;

public Test() {

Container contentPane = getContentPane();

JPanel controlPanel = new JPanel();

JPanel buttonPanel = new JPanel();

JButton doClick = new JButton("do click");

final JButton clickMe = new JButton("click me");

final JComboBox comboBox = new JComboBox(new Object[] {

"68", "250", "500", "750", "1000"

});

controlPanel.add(new JLabel("Click Duration:"));

controlPanel.add(comboBox);

buttonPanel.add(doClick);

buttonPanel.add(clickMe);

contentPane.add(controlPanel, BorderLayout.NORTH);

contentPane.add(buttonPanel, BorderLayout.CENTER);

getRootPane().setDefaultButton(doClick);

doClick.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

clickMe.doClick(clickDuration);

}

});

comboBox.addItemListener(new ItemListener() {

public void itemStateChanged(ItemEvent e) {

if(e.getStateChange() == ItemEvent.SELECTED) {

clickDuration = Integer.parseInt((String)

comboBox.getSelectedItem());

}

});

}

例8-12 JButton图标

import javax.swing.*;

import javax.swing.border.*;

import javax.swing.plaf.basic.*;

import java.awt.*;

import java.awt.event.*;

public class Test extends JApplet {

public void init() {

Container contentPane = getContentPane();

Icon icon = new StringIcon("icon for JButton"),

rolloverIcon = new StringIcon("rollover"),

pressedIcon = new StringIcon("pressed"),

disabledIcon = new StringIcon("disabled"),

selectedIcon = new StringIcon("selected"),

rolloverSelectedIcon =

new StringIcon("rollover selected"),

disabledSelectedIcon =

new StringIcon("disabled selected");

final JButton button = new JButton();

button.setRolloverEnabled(true);

button.setIcon(icon);

button.setRolloverIcon(rolloverIcon);

button.setRolloverSelectedIcon(rolloverSelectedIcon);

button.setSelectedIcon(selectedIcon);

button.setPressedIcon(pressedIcon);

button.setDisabledIcon(disabledIcon);

button.setDisabledSelectedIcon(disabledSelectedIcon);

JComboBox cb = new JComboBox();

cb.addItem("enabled");

cb.addItem("disabled");

cb.addItemListener(new ItemListener() {

public void itemStateChanged(ItemEvent e) {

if(e.getStateChange() == ItemEvent.SELECTED) {

String item = (String)e.getItem();

if(item.equals("enabled")) {

button.setEnabled(true);

}

else {

button.setEnabled(false);

}

});

contentPane.setLayout(new FlowLayout());

contentPane.add(cb);

contentPane.add(button);

}

class StringIcon implements Icon {

private String s;

public StringIcon(String s) {

this.s = s;

}

public int getIconWidth() { return 100; }

public int getIconHeight() { return 100; }

public void paintIcon(Component c, Graphics g, int x, int y) {

FontMetrics fm = g.getFontMetrics();

g.setColor(c.getForeground());

g.drawString(s, 10, fm.getHeight());

}

例8-13 设置按钮边距

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

public class Test extends JApplet {

public Test() {

Container contentPane = getContentPane();

JButton button = new JButton("button");

button.setMargin(new Insets(50,25,10,5));

contentPane.setLayout(new FlowLayout());

contentPane.add(button);

}

例8-14 按钮助记符

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

public class Test extends JApplet {

public Test() {

Container contentPane = getContentPane();

JButton button = new JButton("button With Mnemonic");

button.setMnemonic('M');

contentPane.setLayout(new FlowLayout());

contentPane.add(button);

}

《Java 二 图形设计卷Ⅱ- SWING》第8章

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