我搜索了答案,但我找到的只是工作,而不是原因,所以我问这个问题:
我是GUI编程的新手。在练习一些关于键事件处理的代码时,我遇到了一个JFxt中包含JTextArea的示例。 keylistener接口由Frame本身实现。按下某个键时,根据按下的键,文本区域会显示一些相关信息。代码工作正常。
但我尝试以不同的方式尝试将JTextarea注册到keyListenr而不是JFrame。但是,这不会对关键事件做出响应。这是下面的代码。请帮忙。
public class KeyDemoFrame extends JFrame
{
private String line1 = "";
private String line2 = "";
private String line3 = "";
private JTextArea textArea;
public KeyDemoFrame()
{
super("Demonstrating Keystrong events");
textArea = new JTextArea(10,21);
textArea.setText("Press any key on keyboard");
textArea.setEnabled(false);
textArea.setDisabledTextColor(Color.BLACK);
add(textArea);
//addKeyListener( this );
KeyEventHandler keyStrokeHandler = new KeyEventHandler();
addKeyListener(keyStrokeHandler);
}
private class KeyEventHandler implements KeyListener
{
public void keyPressed(KeyEvent event)
{
line1 = String.format("Your pressed the %s key", KeyEvent.getKeyText(event.getKeyCode()));
setLines2and3(event);
}
public void keyReleased(KeyEvent event)
{
line1 = String.format("You released %s key", KeyEvent.getKeyText(event.getKeyCode()));
setLines2and3(event);
}
public void keyTyped(KeyEvent event)
{
line1 = String.format("You typed %s key",KeyEvent.getKeyText(event.getKeyCode()));
setLines2and3(event);
}
private void setLines2and3(KeyEvent event)
{
line2 = String.format("This key is %san action key", (event.isActionKey()?"":"not "));
String temp = KeyEvent.getKeyModifiersText( event.getModifiers() );
line3 = String.format( "Modifier keys pressed: %s",( temp.equals( "" ) ? "none" : temp ) );
textArea.setText( String.format( "%s\n%s\n%s\n",line1, line2, line3 ) );
}
}
}
import javax.swing.JFrame;
public class KeyDemo
{
public static void main(String[] args)
{
KeyDemoFrame keyDemoFrame = new KeyDemoFrame();
keyDemoFrame.setSize(300, 100);
keyDemoFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
keyDemoFrame.setVisible(true);
}
}
答案 0 :(得分:2)
答案 1 :(得分:2)
此行为的原因是JTextComponent
处理KeyEvent
。正如mKorbel已经指出你应该使用DocumentListener
JTextComponent
s