计算机二级JAVA-98

1、计算机二级JAVA-98（总分：100.00，做题时间：90分钟）一、综合应用题（总题数：3,分数：100.00）按钮改变背景颜色,1. 本程序的功能是定义了自己的组件类。窗口中排布着12个按钮，鼠标移到按钮上时,用鼠标单击按钮时，后台将显示该按钮对应的字符，如图所示。class exam_77 extends Frame String keys="123456789*0#"exam_77() super("exam_77"); addWindowListener(new WindowAdapter() public void windowClosing

2、(WindowEvent e) System.exit(0););setLayout(new GridLayout(4, 3, 6, 6); for ( int i=0; i< keys .l ength; i+ ) KeyButton kb=new KeyButton(keys.charAt(i); kb.addKeyListener(this); kb.setBackground(Color.pink); kb.setForeground(Color.black);add(kb);setSize(200, 200);show();public static void main(Str

3、ing args) new exam_77();class KeyButton extends Component KeyListener keyListener;boolean highlighted;char key;KeyButton(char k) this.key=k; addMouseListener(new MouseEventHandler(); public void paint(Graphics g) int w=getSize().width;int h=getSize().height;String s=""+key;FontMetrics fm=g

4、.getFontMetrics();if (highlighted) g.setColor(getBackground();g.fillRoundRect(O, 0, w-1, h-1, 10, 10);g.setColor(getForeground();g.drawRoundRect(0, 0, w-1, h-1, 10, 10);g.drawString(s, (w-fm.stringWidth(s)/2, (h-fm.getHeight()/2+fm.getAscent();class MouseEventHandler extends MouseAdapter public void

5、 mousePressed(MouseEvent evt) if (keyListener != null) keyListener.keyTyped(new KeyEvent(KeyButton.this, KeyEvent.KEY_TYPED,System.currentTimeMillis(),0, KeyEvent.VK_UNDEFINED, key);public void mouseEntered(MouseEvent evt) highlighted=true;repaint();public void mouseExited(MouseEvent evt) highlighte

6、d=false;repaint();public synchronized void addKeyListener(KeyListener l) keyListener=AWTEventMulticaster.add(keyListener, l);public synchronized void removeKeyListener(KeyListener l) keyListener=AWTEventMulticaster.remove(keyListener, l);(分数：33.00 ) 正确答案：()解析：第 1 处：int i=0; i < keys.length(); i+第

7、 2 处：kb.addKeyListener(new KeyEventHandler()第 3 处：2. 本程序的功能是监听鼠标在哪个组件上方。窗口中有四个按钮和一个文本标签，当鼠标移到其中一个按 钮上面时，文本标签将显示在按钮上显示的对应提示信息，如图所示。class exam_78 extends Frame Label statusbar=new Label("Ready");exam_78() super("exam_78");addWindowListener(new WindowAdapter() public void windowClos

8、ing(WindowEvent e) System.exit(O););MainButton b;mhandler=new MouseEventHandler();Panel toolbar=new Panel(new FlowLayout();b=new MainButton("Create", "Create a new document.");b.addMouseListener(mhandler);toolbar.add(b);b=new MainButton("Open", "Open an existing do

9、cument."); b.addMouseListener(mhandler);toolbar.add(b);b=new MainButton("Save", "Save the current document."); b.addMouseListener(mhandler);toolbar.add(b);b=new MainButton("Close", "Close the current document.");b.addMouseListener(mhandler);toolbar.add(b)

10、;add(toolbar, BorderLayout.CENTER);add(statusbar, BorderLayout.SOUTH);pack();show();class MouseEventHandler extends MouseAdapter public void mouseOvered(MouseEvent evt) statusbar.setText(MainButton)evt.getSource().getDescription();public void mouseExited(MouseEvent evt) statusbar.setText(null);publi

11、c static void main(String args) new exam_78();class MainButton extends Button String desc;MainButton(String label) super(label); this.desc=desc;String getDescription() return desc;(分数：33.00 ) 正确答案：()解析：第 1 处： MouseEventHandler mhandler = new MouseEventHandler()第 2 处：public void mouseEntered(MouseEve

12、nt evt)第 3 处：MainButton(String label, String desc)3. 本程序的功能是监听鼠标在窗口中的位置和操作。程序窗口背景色为黄色，窗口中有四个方向不同的白 色三角形，当鼠标置于其中一个三角形上时，三角形变为红色，当鼠标按键按下时，三角形变为蓝色，当 鼠标按钮松开或鼠标移开后，颜色恢复原样，如图所示。public class exam_79 extends Frame exam_79() super("exam_79");addWindowListener(new WindowAdapter() public void windowC

13、losing(WindowEvent e) System.exit(0););Component c;setBackground(yellow);GridBagLayout gbl=new GridBagLayout();setLayout(gbl);add(c=new ArrowButton(ArrowButton.NORTH);setConstraints(gbl, c, 1,0);add(c=new ArrowButton(ArrowButton.WEST);setConstraints(gbl, c, 0, 1);add(c=new ArrowButton(ArrowButton.SO

14、UTH);setConstraints(gbl, c, 1,2);add(c=new ArrowButton(ArrowButton.EAST);setConstraints(gbl, c, 2, 1);pack();show();void setConstraints(GridBagLayout gbl, Component comp, int x, int y) GridBagConstraints cbc=new GridBagConstraints();cbc.gridx=x;cbc.gridy=y;cbc.insets=new Insets(2, 2, 2, 2);gbl.setCo

15、nstraints(comp, cbc);public static void main(String args) new exam_79();ArrowButton extends Component implements MouseListener static final int NORTH=0;static final int WEST=1;static final int SOUTH=2;static final int EAST=3;corners=1,0, 0, 0, 0,1, 1,1 ;double tips=.5, 0, 0, .5, .5, 1, 1, .5;int wid

16、th=30;int height=30;int orient;boolean highlight;boolean down;Polygon shape=new Polygon();ArrowButton(int o) orient=o;int o1=(o+1)% corners.length;int o2=(o+2)% corners.length;int o3=(o+3)% corners.length;int w=width-1;int h=height-1;shape.addPoint(int) (tipso0*w), (int) (tipso1*h); shape.addPoint(c

17、ornerso20*w, cornerso21*h); shape.addPoint(cornerso30*w, cornerso31*h); addMouseListener(this);public void paint(Graphics g) if (highlight) if (down) g.setColor(Color.blue); else g.setColor(Color.red); else g.setColor(Color.white);g.fillPolygon(shape);g.setColor(Color.black);g.drawPolygon(shape);pub

18、lic void mouseClicked(MouseEvent evt) public void mousePressed(MouseEvent evt) down=true;repaint();public void mouseReleased(MouseEvent evt) if (down) processActionEvent(new ActionEvent(this, ActionEvent.ACTION_PERFORMED, ""+orient);down=false; repaint();public void mouseEntered(MouseEvent evt) highlight=true;repaint();public void mouseExited(MouseEvent evt) highlight=false;repaint();public boolean contains(int x, int y) return shape.contains(x, y);public Dimension getMinimumSize() return new Dimension(width, height);public Dimen