swing 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);
	}
}