Java Swing JTextArea插入符号拒绝移动到左上角

Question

private void jTextArea2KeyPressed(java.awt.event.KeyEvent evt) {                                      
    if(evt.getKeyCode() == KeyEvent.VK_ENTER){
        try {
            sendCommand("hf", "ab4mw", jTextArea2.getText().trim());
            jTextArea1.append(TX + jTextArea2.getText().trim() + nl);
            jTextArea2.setText("");
            System.out.println("carat: " + jTextArea2.getCaretPosition());
            System.out.println("length: " + jTextArea2.getText().length());
            jTextArea2.setCaretPosition(0);
            //jTextArea2.moveCaretPosition(0);
            System.out.println("line: " + jTextArea2.getLineCount());
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
}

...无限。

我是不是错过了一些简单的东西？

Answer 1

将public void keyPressed（KeyEvent e）{方法更改为

public void keyReleased(KeyEvent e) {

好吧，为什么这只发生在按下键的上？我不太确定，但我的猜测是JTextArea首先处理JTextareA2.SetCaretPosition(0)；之后才会中断行（在TextArea中enter键自然会这样做）。当keyrelease时，情况显然不是这样，然后它在断行后调用jtextarea2.setcaretposition(0)；，这就是您想要的。

下面是一个例子：

import java.awt.Color;
import java.awt.GridLayout;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;

import javax.swing.JFrame;
import javax.swing.JTextArea;
import javax.swing.border.LineBorder;

public class Example extends JFrame {

    public Example() {

        JFrame frame = new JFrame();
        frame.setLayout(new GridLayout(2,0));

        JTextArea jTextArea1 = new JTextArea();
        jTextArea1.addKeyListener(new KeyAdapter() {
            public void keyPressed(KeyEvent e) {
                if (e.getKeyCode() == KeyEvent.VK_ENTER) {
                    jTextArea1.setText("");
                    System.out.println("carat: "
                            + jTextArea1.getCaretPosition());
                    System.out.println("length: "
                            + jTextArea1.getText().length());
                    jTextArea1.setCaretPosition(0);
                    // jTextArea2.moveCaretPosition(0);
                    System.out.println("line: " + jTextArea1.getLineCount());
                }
            }
        });
        jTextArea1.setBorder(new LineBorder(Color.BLACK));
        jTextArea1.setText("This TextArea will not work like you want it to");

        JTextArea jTextArea2 = new JTextArea();
        jTextArea2.addKeyListener(new KeyAdapter() {
            public void keyReleased(KeyEvent e) {
                if (e.getKeyCode() == KeyEvent.VK_ENTER) {
                    jTextArea2.setText("");
                    System.out.println("carat: "
                            + jTextArea2.getCaretPosition());
                    System.out.println("length: "
                            + jTextArea2.getText().length());
                    jTextArea2.setCaretPosition(0);
                    // jTextArea2.moveCaretPosition(0);
                    System.out.println("line: " + jTextArea2.getLineCount());
                }
            }
        });
        jTextArea2.setBorder(new LineBorder(Color.BLACK));
        jTextArea2.setText("This TextArea WILL");

        frame.add(jTextArea1);
        frame.add(jTextArea2);
        frame.setSize(500, 500);
        frame.setVisible(true);

    }

    public static void main(String[] args) {
        new Example();
    }
}