Question

在我的应用程序中，当用户单击JButton时，显示一个提示用户输入整数的JLabel，一个用户可以输入整数的JTextField，以及一个包含Double me文本的secondJButton。当用户单击第二个按钮时，整数加倍，答案显示在JTextField中。

当我点击第一个按钮时，我无法显示第二个按钮和文本字段...请帮助

import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JApplet;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JTextField;


public class JDouble extends JApplet implements ActionListener {
    private Container container = getContentPane();

    /**
     * The JButton.
     */
    private JButton button = new JButton("Click me");
    private JButton button2 = new JButton("Double me");

    /**
     * The JLabel.
     */
    private JLabel label = new JLabel("Enter Integer");
    private JTextField textfield = new JTextField(4);
    private JTextField textfield2 = new JTextField(4);

    public void init() {
        // set the layout to FlowLayout
        container.setLayout(new FlowLayout());

        // register the 'this' action listener for the button
        button.addActionListener(this);

        container.add(button);
    }

    public void init1(){
        container.setLayout(new FlowLayout());
        container.add(textfield);
        container.add(button2);
        container.add(textfield2);
        button2.addActionListener(this);
    }

    public void actionPerformed(ActionEvent actionEvent) {
        container.add(label);
    }

    public void actionPerformed1(ActionEvent actionEvent) {
        String me = textfield.getText();
        int computation = Integer.parseInt(me);
        computation = computation*2;
        String changecomputation = Integer.toString(computation);
        textfield2.setText(changecomputation);
        container.remove(button);

        container.add(label);

        repaint();
        validate();
    }

}

Answer 1

你的init（）方法：

   public void init() {  
        // set the layout to FlowLayout
        container.setLayout(new FlowLayout());
        // register the 'this' action listener for the button
        button.addActionListener(this);
        container.add(button);
}

我们将使用此功能在单击“Click Me”时显示其他字段...

  private showInputFields(){
        container.add(textfield);
        button2.addActionListener(this);
        container.add(button2);
        container.add(textfield2);
  }

让我们修复你的动作监听器。如果您想在启动时显示“Click Me”按钮，init()会处理此问题。当用户点击“Click Me”时，我们会调用showInputFields()来显示其他组件;我们会处理“Double me”点击使用相同的监听器，我们只需检查事件源以便正确处理......

    private boolean inputFieldsDisplayed; 
    public void actionPerformed(ActionEvent actionEvent) {
        if( actionEvent.getSource() == button && !inputFieldsDisplayed){
            showInputFields();
            inputFieldsDisplayed = true;

        } else if ( actionEvent.getSource() == button2){                
            String me = textfield.getText();
            int computation = Integer.parseInt(me);
            computation = computation*2;
            String changecomputation = Integer.toString(computation);
            textfield2.setText(changecomputation);                
        }
        validate();
        repaint();            
    }

Java applet布局和动作处理程序问题

1 个答案: