从另一个类更改JLabel上的文本

所以，我一直试图弄清楚这一点，但无法弄清楚如何做到这一点。 我想在另一个类中使用我的一个按钮来更改GUI类中JLabel的文本。

以下是GUI类的代码：`import java.awt.Container;

import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JTextField; public class GUI extends JFrame{ Container pane = getContentPane(); JButton guess = new JButton("Guess"); JButton gen = new JButton("Generate number"); JTextField userInput = new JTextField(); JLabel Numbers = new JLabel("Press generate to start."); JLabel guessedNum = new JLabel(""); JLabel error = new JLabel(""); public void CreateGUI(){ final int WIDTH = 325; final int HEIGHT = 200; final int centerWIDTH = WIDTH / 4; final int centerHEIGHT = HEIGHT / 4; guessHandler guessHandle; genHandler genHandle; pane.setLayout(null); guessHandle = new guessHandler(); guess.addActionListener(guessHandle); genHandle = new genHandler(); gen.addActionListener(genHandle); userInput.setBounds(centerWIDTH - 20, centerHEIGHT, 200, 20); guess.setBounds(userInput.getX() - 35, (userInput.getY() + 25), 105, 50); gen.setBounds((guess.getX() + 105), guess.getY(), 165, 50); error.setBounds(70, 125, 300, 20); Numbers.setBounds(90, 0, 300, 20); guessedNum.setBounds(20, 25, 300, 20); pane.add(userInput); pane.add(guess); pane.add(gen); pane.add(Numbers); pane.add(guessedNum); pane.add(error); setSize(WIDTH,HEIGHT); setTitle("Number Guesser"); setDefaultCloseOperation(EXIT_ON_CLOSE); setVisible(true); setResizable(false); setLocation(350, 150); } } 

这里来自按钮的代码试图改变JLabel“错误”：`

 import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import javax.swing.JButton; import javax.swing.JLabel; import javax.swing.JTextField; public class guessHandler implements ActionListener{ public void actionPerformed(ActionEvent e) { GUI gui = new GUI(); gui.changePOS(4, 50, 0, 300, 20); gui.error.setText("HI from guessHandler.java"); } } 

Answer 1

首先，添加一个具有public访问权限的getter，以便您的第二个类可以访问该字段。 就像是，

 public JLabel getError() { return error; } 

或者（正如@MadProgrammer在评论中建议的，一个变异者）喜欢

 public void setError(String txt) { error.setText(txt); } 

然后修改你的第二个类，并在构造函数中将GUI实例传递给它。 喜欢，

 public class guessHandler implements ActionListener{ private GUI gui; public guessHandler(GUI gui) { this.gui = gui; } public void actionPerformed(ActionEvent e) { gui.changePOS(4, 50, 0, 300, 20); gui.setError("HI from guessHandler.java"); } }