取消选择JTextfield上的默认选择

Question

使用JTextFields时，我喜欢设置默认文本。

然后我运行程序，这个默认文本会自动被选中（至少当你只有一个字段时）。换句话说，如果我马上输入一个字母，默认的文字将被删除并被新的字母替换。

我的问题是我如何改变默认设置，让我键入一个字母而不删除默认文本？我希望这封信可以添加在默认文本的末尾。

这里是我的代码：

public class ButtonsNText extends JPanel implements ActionListener, KeyListener { 

private JTextField TextLine; 
private JToggleButton UpperCaseButton; 
private JToggleButton LowerCaseButton; 
private JCheckBox ContinuousButton; 
private ButtonGroup myButtonGroup; 

public ButtonsNText(){ 
    TextLine = new JTextField(10); 
    add(TextLine); TextLine.setName("TextLine"); 
    TextLine.setText("default text"); 
    TextLine.setCaretPosition(TextLine.getText().length()); 
    TextLine.addKeyListener(this); 
    myButtonGroup = new ButtonGroup(); 
    UpperCaseButton = new JToggleButton("Upper case"); 
    add(UpperCaseButton);UpperCaseButton.setName("UpperCaseButton"); 
    LowerCaseButton = new JToggleButton("Lower case"); 
    add(LowerCaseButton); LowerCaseButton.setName("LowerCaseButton"); 
    ContinuousButton = new JCheckBox("Continuous?"); 
    add(ContinuousButton); ContinuousButton.setName("ContinuousButton"); 
    myButtonGroup.add(UpperCaseButton); myButtonGroup.add(LowerCaseButton); 
    UpperCaseButton.addActionListener(this); 
    LowerCaseButton.addActionListener(this); 
    ContinuousButton.addActionListener(this); 

} 
public static void main(String[] args) { 
    JFrame frame = new JFrame("Hello world example"); 
    frame.add(new ButtonsNText()); 
    frame.pack(); 
    frame.setVisible(true); 
} 
@Override 
public void actionPerformed(ActionEvent e) { 
    if(e.getSource() == UpperCaseButton){ 
     TextLine.setText(TextLine.getText().toUpperCase()); 
    } 
    else if(e.getSource() == LowerCaseButton){ 
     TextLine.setText(TextLine.getText().toLowerCase()); 
    } 
} 
@Override 
public void keyReleased(KeyEvent k) { 
    if(ContinuousButton.isSelected()){ 
     if(UpperCaseButton.isSelected()){ 
      int pos = TextLine.getCaretPosition(); 
      TextLine.setText(TextLine.getText().toUpperCase()); 
      TextLine.setCaretPosition(pos); 
     } 
     else if(LowerCaseButton.isSelected()){ 
      int pos = TextLine.getCaretPosition(); 
      TextLine.setText(TextLine.getText().toLowerCase()); 
      TextLine.setCaretPosition(pos); 

     } 
    } 
    int key = k.getKeyCode(); 
    if(key == KeyEvent.VK_ENTER){ 
     if(UpperCaseButton.isSelected()){ 
      TextLine.setText(TextLine.getText().toUpperCase()); 
     } 
     else if(LowerCaseButton.isSelected()){ 
      TextLine.setText(TextLine.getText().toLowerCase()); 
     } 
    } 
} 

}

我试图像isFocusable（），setFocusable（），setCaterPosition（）和其他类似方法的东西，但在这里，我想我需要一个不同的方法。

Answer 1

，将被删除

import java.awt.*; 
import javax.swing.*; 
import javax.swing.text.DefaultCaret; 
import javax.swing.text.DefaultHighlighter; 
import javax.swing.text.Highlighter; 

public class TestTextComponents extends JFrame { 

    private static final long serialVersionUID = 1L; 
    private JTextField jTextField1; 
    private JTextField jTextField2; 

    public TestTextComponents() { 
     initComponents(); 
    } 

    private void initComponents() { 
     jTextField1 = new JTextField(); 
     jTextField2 = new JTextField(); 
     getContentPane().setLayout(new FlowLayout()); 
     setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE); 
     setTitle("Text component persistent selection"); 
     setResizable(false); 
     getContentPane().add(new JLabel(
       "Please skip between text fields and watch persistent selection: ")); 
     jTextField1.setText("jTextField1"); 
     getContentPane().add(jTextField1); 
     jTextField2.setText("jTextField2"); 
     getContentPane().add(jTextField2); 
     jTextField1.setCaret(new HighlightCaret()); 
     jTextField2.setCaret(new HighlightCaret()); 
     //Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize(); 
     // setBounds((screenSize.width - 600)/2, (screenSize.height - 70)/2, 600, 70); 
    } 

    public static void main(String args[]) { 
     SwingUtilities.invokeLater(new Runnable() { 

      @Override 
      public void run() { 
       new TestTextComponents().setVisible(true); 
      } 
     }); 
    } 
} 

class HighlightCaret extends DefaultCaret { 

    private static final Highlighter.HighlightPainter unfocusedPainter = 
      new DefaultHighlighter.DefaultHighlightPainter(new Color(230, 230, 210)); 
    private static final long serialVersionUID = 1L; 
    private boolean isFocused; 

    @Override 
    protected Highlighter.HighlightPainter getSelectionPainter() { 
     return isFocused ? super.getSelectionPainter() : unfocusedPainter; 
    } 

    @Override 
    public void setSelectionVisible(boolean hasFocus) { 
     if (hasFocus != isFocused) { 
      isFocused = hasFocus; 
      super.setSelectionVisible(false); 
      super.setSelectionVisible(true); 
     } 
    } 
} 

Answer 2

如果您将脱字号移动到最后？

txt.setCaretPosition(txt.getText().length()); 

Answer 3

只需添加对焦一个的FocusListener后获得了，这会为你tfield2.setCaretPosition一起做（tfield2.getDocument（）的getLength（））; 这里看到您的帮助代码：为@Pete

import java.awt.event.*; 

import javax.swing.*; 

public class TextFieldExample extends JFrame 
{ 
    public TextFieldExample() 
    { 
     setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     setLocationRelativeTo(null); 

     JPanel contentPane = new JPanel(); 
     JTextField tfield = new JTextField(10); 
     final JTextField tfield2 = new JTextField(10); 
     tfield2.setText("default text"); 
     tfield2.addFocusListener(new FocusListener() 
     { 
      public void focusGained(FocusEvent fe) 
      { 
       tfield2.setCaretPosition(tfield2.getDocument().getLength()); 
      } 

      public void focusLost(FocusEvent fe) 
      { 
      } 
     }); 

     contentPane.add(tfield); 
     contentPane.add(tfield2); 

     setContentPane(contentPane); 

     pack(); 
     setVisible(true); 
    } 

    public static void main(String... args) 
    { 
     SwingUtilities.invokeLater(new Runnable() 
     { 
      public void run() 
      { 
       new TextFieldExample(); 
      } 
     }); 
    } 
}