一个更复杂的Bean

接下的程序例子稍微复杂一些，尽管这没有什么价值。这个程序是一张不论鼠标何时移动都围绕它画一个小圆的，并且一个动作接收器被激活。画布。当按下鼠标键时，我们可以改变的属性是圆的大小，除此之外还有被显示文字的色彩，大小，内容。BangBean同样拥有它自己的addActionListener()和removeActionListener()方法，因此我们可以附上自己的当用户单击在BangBean上时会被激活的接收器。这样，我们将能够确认可支持的属性和事件：//: BangBean.java// A graphical Beanpackage bangbean;import java.awt.*;import java.awt.event.*;import java.io.*;import java.util.*;

public class BangBean extends Canvas implements Serializable { protected int xm, ym; protected int cSize = 20; // Circle size protected String text = "Bang!"; protected int fontSize = 48; protected Color tColor = Color.red; protected ActionListener actionListener; public BangBean() { addMouseListener(new ML()); addMouseMotionListener(new MML()); } public int getCircleSize() { return cSize; } public void setCircleSize(int newSize) { cSize = newSize; } public String getBangText() { return text; } public void setBangText(String newText) { text = newText; } public int getFontSize() { return fontSize; } public void setFontSize(int newSize) { fontSize = newSize; } public Color getTextColor() { return tColor; } public void setTextColor(Color newColor) { tColor = newColor; } public void paint(Graphics g) { g.setColor(Color.black); g.drawOval(xm - cSize/2, ym - cSize/2, cSize, cSize); } // This is a unicast listener, which is // the simplest form of listener management: public void addActionListener ( ActionListener l) throws TooManyListenersException { if(actionListener != null) throw new TooManyListenersException(); actionListener = l; } public void removeActionListener( ActionListener l) { actionListener = null; } class ML extends MouseAdapter { public void mousePressed(MouseEvent e) { Graphics g = getGraphics(); g.setColor(tColor); g.setFont( new Font( "TimesRoman", Font.BOLD, fontSize)); int width = g.getFontMetrics().stringWidth(text); g.drawString(text, (getSize().width - width) /2, getSize().height/2); g.dispose(); // Call the listener''s method: if(actionListener != null) actionListener.actionPerformed( new ActionEvent(BangBean.this, ActionEvent.ACTION_PERFORMED, null)); } } class MML extends MouseMotionAdapter { public void mouseMoved(MouseEvent e) { xm = e.getX(); ym = e.getY(); repaint(); } } public Dimension getPreferredSize() { return new Dimension(200, 200); } // Testing the BangBean: public static void main(String[] args) { BangBean bb = new BangBean(); try { bb.addActionListener(new BBL()); } catch(TooManyListenersException e) {} Frame aFrame = new Frame("BangBean Test"); aFrame.addWindowListener( new WindowAdapter() { public void windowClosing(WindowEvent e) { System.exit(0); } }); aFrame.add(bb, BorderLayout.CENTER); aFrame.setSize(300,300); aFrame.setVisible(true); } // During testing, send action information // to t

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