java退格键运行代码 java里面如何退格( 二 )


private String lastCommand;//保存+,-,*,/,=命令0
private double result;//保存计算结果
private boolean start;//判断是否为数字的开始
private JMenuBar menubar;
private JMenuItem m_exit,m2_ejz,m2_bjz;
private Dialog dialog;
private Label label_dialog;
private JButton button_sqrt,button_plusminus,button_CE,button_cancel,button_1,button_2,
button_3,button_4,button_5,button_6,button_7,button_8,button_9,button_0,
button_plus,button_minus,button_multiply,button_divide,button_point,
button_equal,button_log,button_tan,button_cos,button_sin,button_exp;
public Calculator()//构造方法设置布局、为按钮注册事件监听器
{
super("Calculator");
this.setLocation(240,200);
this.setSize(350,300);
this.setResizable(true);
this.setLayout(new GridLayout(7,1));
this.addmyMenu();//调用成员方法添加菜单
displayField=new JTextField(30);
this.add(displayField);
displayField.setEditable(true);
start=true;
result=0;
lastCommand = "=";
JPanel panel0=new JPanel();
panel0.setLayout(new GridLayout(1,4,4,4));
JPanel panel1=new JPanel();
panel1.setLayout(new GridLayout(1,5,4,4));
this.add(panel1);
button_sqrt=new JButton("sqrt");
button_plusminus=new JButton("+/-");
button_exp=new JButton("exp");
button_CE=new JButton("退格");
button_cancel=new JButton("C");
JPanel panel2=newJPanel();
panel2.setLayout(new GridLayout(1,5,4,4));
this.add(panel2);
button_7=new JButton("7");
button_8=new JButton("8");
button_9=new JButton("9");
button_log=new JButton("log");
button_divide=new JButton("/");
JPanel panel3=new JPanel();
panel3.setLayout(new GridLayout(1,5,4,4));
this.add(panel3);
button_4=new JButton("4");
button_5=new JButton("5");
button_6=new JButton("6");
button_tan=new JButton("tan");
button_multiply=new JButton("*");
JPanel panel4=newJPanel();
panel4.setLayout(new GridLayout(1,5,4,4));
this.add(panel4);
button_1=new JButton("1");
button_2=new JButton("2");
button_3=new JButton("3");
button_cos=new JButton("cos");
button_minus=new JButton("-");
JPanel panel5=newJPanel();
panel5.setLayout(new GridLayout(1,5,4,4));
this.add(panel5);
button_0=new JButton("0");
button_point=new JButton(".");
button_equal=new JButton("=");
button_sin=new JButton("sin");
button_plus=new JButton("+");
panel1.add(button_sqrt);
panel1.add(button_plusminus);
panel1.add(button_exp);
panel1.add(button_CE);
panel1.add(button_cancel);
panel2.add(button_7);
panel2.add(button_8);
panel2.add(button_9);
panel2.add(button_log);
panel2.add(button_divide);
panel3.add(button_4);
panel3.add(button_5);
panel3.add(button_6);
panel3.add(button_tan);
panel3.add(button_multiply);
panel4.add(button_1);
panel4.add(button_2);
panel4.add(button_3);
panel4.add(button_cos);
panel4.add(button_minus);
panel5.add(button_0);
panel5.add(button_point);
panel5.add(button_equal);
panel5.add(button_sin);
panel5.add(button_plus);
button_sqrt.addActionListener(this);
button_plusminus.addActionListener(this);
button_exp.addActionListener(this);
button_CE.addActionListener(this);
button_cancel.addActionListener(this);
button_7.addActionListener(this);
button_8.addActionListener(this);
button_9.addActionListener(this);
button_log.addActionListener(this);
button_divide.addActionListener(this);
button_4.addActionListener(this);
button_5.addActionListener(this);
button_6.addActionListener(this);
button_tan.addActionListener(this);
button_multiply.addActionListener(this);

推荐阅读