[英]How to add an ActionListener to a button in a frame in Java
我正在尝试测试按钮,但无法使动作监听器正常工作
public class ButtonTester implements ActionListener {
static JLabel Label = new JLabel("Hello Buttons! Will You Work?!");
public static void main(String[] args) {
//Creating a Label for step 3
// now for buttons
JButton Button1 = new JButton("Test if Button Worked");
// step 1: create the frame
JFrame frame = new JFrame ("FrameDemo");
//step 2: set frame behaviors (close buttons and stuff)
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//step 3: create labels to put in the frame
frame.getContentPane().add(Label, BorderLayout.NORTH);
frame.getContentPane().add(Button1, BorderLayout.AFTER_LAST_LINE);
//step 4: Size the frame
frame.pack();
//step 5: show the frame
frame.setVisible(true);
Button1.setActionCommand("Test");
Button1.setEnabled(true);
Button1.addActionListener(this); //this line here won't work
}
@Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
if("Test".equals(e.getActionCommand()))
{
Label.setText("It Worked!!!");
}
}
}
this
已经在没有上下文static
方法
而是尝试使用类似Button1.addActionListener(new ButtonTester());
代替...
更新
您可能还想看看Initial Threads,因为Swing有一些特殊要求。
静态方法不是一类的实例相关联,因此this
不能使用。
您可以将所有代码从main移到ButtonTester的非静态方法(例如, run()
,然后从main执行以下操作:
new ButtonTester().run();
您还可以为ActionListener使用匿名内部类:
Button1.addActionLister(new ActionListener() {
@Override public void actionPerformed (ActionEvent e) {
// ...
}
});
Java表示您不能从静态上下文访问非静态实体(这是指非静态且main()是静态的对象),因此我们使用构造函数进行初始化:
public class ButtonTester implements ActionListener {
static JLabel Label = new JLabel("Hello Buttons! Will You Work?!");
ButtonTester() //constructor
{
//Creating a Label for step 3
// now for buttons
JButton Button1 = new JButton("Test if Button Worked");
// step 1: create the frame
JFrame frame = new JFrame ("FrameDemo");
//step 2: set frame behaviors (close buttons and stuff)
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//step 3: create labels to put in the frame
frame.getContentPane().add(Label, BorderLayout.NORTH);
frame.getContentPane().add(Button1, BorderLayout.AFTER_LAST_LINE);
//step 4: Size the frame
frame.pack();
//step 5: show the frame
frame.setVisible(true);
Button1.setActionCommand("Test");
Button1.setEnabled(true);
Button1.addActionListener(this); //this line here won't work
}
public static void main(String[] args) {
ButtonTester test1=new ButtonTester();// constructor will be invoked and new object created
}
@Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
if("Test".equals(e.getActionCommand()))
{
Label.setText("It Worked!!!");
}
}
}
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.