test.java

《Java2图形设计卷II：Swing》配套光盘源码

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;

public class Test extends JApplet {
	private JScrollBar vsb = new JScrollBar(JScrollBar.VERTICAL);
	private SSPanel panel = new SSPanel();

	public Test() {
		Container contentPane = getContentPane();

		contentPane.add(panel, BorderLayout.CENTER);
		contentPane.add(vsb, BorderLayout.EAST);

		vsb.addAdjustmentListener(new AdjustmentListener() {
			public void adjustmentValueChanged(
											 AdjustmentEvent e) {
				JScrollBar sb = (JScrollBar)e.getSource();
				showScrollBarValues();
				panel.setTopIndexByPixelValue(e.getValue());
				panel.repaint();
			}
		});
	}
	public void paint(Graphics g) {
		Dimension pref = panel.getPreferredSize();
		Dimension size = panel.getSize();
		int extent = size.height, max = pref.height;
		int value = Math.max(0, 
						Math.min(vsb.getValue(), max - extent));

		vsb.setVisible(extent < max);
		vsb.setUnitIncrement(panel.getUnitHeight());
		vsb.setBlockIncrement(extent - vsb.getUnitIncrement());
		vsb.setValues(value, extent, 0, max);

		showScrollBarValues();
		super.paint(g);
	}
	private void showScrollBarValues() {
		showStatus("min: " + vsb.getMinimum() +
					", max: " + vsb.getMaximum() +
					", visible amount: " + 
					vsb.getVisibleAmount() +
					", value: " + vsb.getValue());
	}
}
class SSPanel extends JPanel { 
	private int topIndex = 0;
	private int fh;

	private String[] data = {
		"Brown, Ted:  000-00-0001", "Brown, Ted:  000-00-0002",
		"Brown, Ted:  000-00-0003", "Brown, Ted:  000-00-0004",
		"Brown, Ted:  000-00-0005", "Brown, Ted:  000-00-0006",
		"Brown, Ted:  000-00-0007", "Brown, Ted:  000-00-0008",
		"Brown, Ted:  000-00-0009", "Brown, Ted:  000-00-00010",
		"Brown, Ted:  000-00-00011", "Brown, Ted:  000-00-00012",
		"Brown, Ted:  000-00-00013", "Brown, Ted:  000-00-00014",
		"Brown, Ted:  000-00-00015", "Brown, Ted:  000-00-00016",
		"Brown, Ted:  000-00-00017", "Brown, Ted:  000-00-00018",
		"Brown, Ted:  000-00-00019", "Brown, Ted:  000-00-00020",
		"Brown, Ted:  000-00-00021", "Brown, Ted:  000-00-00022",
		"Brown, Ted:  000-00-00023", "Brown, Ted:  000-00-00024",
		"Brown, Ted:  000-00-00025", "Brown, Ted:  000-00-00026",
		"Brown, Ted:  000-00-00027", "Brown, Ted:  000-00-00028",
		"Brown, Ted:  000-00-00029", "Brown, Ted:  000-00-00030",
	};
	public void paintComponent(Graphics g) {
		Color color = g.getColor();
		super.paintComponent(g);
		g.setColor(color);

		Dimension size = getSize();
		Insets insets = getInsets();
		int y = insets.top;

		for(int i = topIndex; i < data.length; ++i, y += fh) {
			g.drawString(data[i], 0, y);

			if(y + fh > size.height - insets.bottom)
				break;
		}
	}
	public void setTopIndexByPixelValue(int pixelValue) {
		topIndex = pixelValue / fh;
	}
	public int getUnitHeight() {
		return fh;
	}
	public Dimension getPreferredSize() {
		Dimension dim = new Dimension();
		Graphics g = getGraphics();

		try {
			FontMetrics fm = g.getFontMetrics();
			fh = fm.getHeight();

			dim.width = fm.stringWidth(data[data.length-1]);
			dim.height = fm.getHeight() * (data.length + 1);
		}
		finally {
			g.dispose();
		}
		return dim;
	}
}