问题1：看下面代码
import java.awt.*;
import java.awt.event.*;
class Calculate extends Frame implements ActionListener {
TextField t1 = new TextField(5);
TextField t2 = new TextField(5);
TextField t3 = new TextField(5);
TextField t4 = new TextField(5);
Label L1 = new Label("=");
Button btn = new Button("计算");
Label L2 = new Label("第一个框里添被运算数，第二个框里添运算符仅限+、-、*、/四个, 第三个框里添运算数，按计算按扭结果会在第四个框中显示出来。老师让我做个类似windows计算器的GUI程序，呵呵，偷懒了。");
//为什么上面实例化的两个对象L1和L2没有正常的显示出来？？？？？？？？？？？？？？？？？？？？？？？？？
//编译是通过的
public Calculate() {
setLayout(new FlowLayout());
add(t1);
add(t2);
add(t3);
add(t4);
add(btn);
btn.addActionListener(this);
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
dispose();
System.exit(0);
}
});
}
public void actionPerformed(ActionEvent e) {
float x,y;
double result = 0;
String op;
try {
x = Float.parseFloat(t1.getText());
y = Float.parseFloat(t3.getText());
op = t2.getText();
if (op.equals("+")) {result = x + y;}
else if (op.equals("-")) {result = x - y;}
else if (op.equals("*")) {result = x * y;}
else if (op.equals("/")) {result = x / y;}
t4.setText(Double.toString(result));
}
catch(Exception ee){
t4.setText("数据类型错误！");
}
}
public static void main (String args[]) {
Calculate mainFrame = new Calculate();
mainFrame.setSize(500,150);
mainFrame.setTitle("musicyxy计算程序");
mainFrame.setVisible(true);
}
}
问题2：看下面代码
这是段Swing代码，目的是显示个加载程序的界面。
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class SplashWindow extends JWindow implements ActionListener {
JLabel back = new JLabel(new ImageIcon("back.jpg"));
JProgressBar progressBar = new JProgressBar(1,100);
Timer timer;
int n = 100;
public SplashWindow() {
setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));
progressBar.setStringPainted(true);
progressBar.setString("loading..........");
getContentPane().add(back,"Center");
getContentPane().add(progressBar,"South");
setSize(300,200);
toFront();
setLoaction(200,200); //编译到这个地方有了问题。下面是编译出错信息，为什么会有这样的信息呢？？？？？？
//cannot resolve symbol
//symbol : method setLocation(int,int)
// location : class SplashWindow
setLocation(200,200);
// ^
setVisible(true);
timer = new javax.swing.Timer(100,this);
timer.addActionListener(this);
timer.start();
}
public void actionPerformed(ActionEvent e) {
if(--n > 0) {
progressBar.setValue(100-n);
timer.restart();
}
else {
timer.stop();
dispose();
}
}
public static void main(String args[]) {
SplashWindow splashWindow = new SplashWindow();
}
}
