某些东西似乎与试图设置字符串变量的代码块有关,不管我在运行程序时做什么,对话框总是显示otto。有谁知道我在这里做错了吗?java初学者if/else如果问题
感谢, 猎食
import java.awt.FlowLayout;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.JOptionPane;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;
public class SmallTingz extends JFrame {
private JLabel item1;
private JTextField tf;
private JTextField tf2;
private JTextField tf3;
private JPasswordField pf;
public SmallTingz() {
super("The Title");
setLayout(new FlowLayout());
JTextField tf = new JTextField("Cool Beans");
JTextField tf2 = new JTextField("UnCool Beans");
JTextField tf3 = new JTextField("Hot Beans");
JPasswordField pf = new JPasswordField("password");
add(tf);
add(tf2);
add(tf3);
add(pf);
thehandler handler = new thehandler();
tf.addActionListener(handler);
tf2.addActionListener(handler);
tf3.addActionListener(handler);
pf.addActionListener(handler);
}
private class thehandler implements ActionListener {
public void actionPerformed(ActionEvent event) {
String string;
if (event.getSource() == tf)
string=String.format("field1: %s", event.getActionCommand());
else if (event.getSource() == tf2)
string=String.format("field2: %s", event.getActionCommand());
else if (event.getSource() == tf3)
string=String.format("field3: %s", event.getActionCommand());
else if (event.getSource() == pf)
string=String.format("passfield: %s", event.getActionCommand());
else
string="otto";
JOptionPane.showMessageDialog(null, string);
}
}
}
您应该在if语句中使用“.equals()”而不是“==”。例如if(event.getSource()。equals(tf))“tf”和“event.getSource()”必须是相同类型 – fsonmezay
尝试通过调试器运行此操作,打破actionPerformed。然后检查事件的运行时间值。 – jpm
@fsonmezay getSource()返回发出源的实际组件的引用。因此,在这种情况下,对参考平等进行测试实际上是正确的。否则,如果您有两个subl压缩的JButton,其overrode等于基于它们的标签,则无法区分两个不同按钮之间按下等同标签的区别。 – jpm