标签:jtextarea swing key-bindings backspace java
我有一个在特定设置下不可编辑的JTextArea.但是,在此设置下,用户仍然可以使用空格键和退格键.为了容纳空间,我有以下代码,
if (e.getKeyChar() == KeyEvent.VK_SPACE) {
editor.insert(" ", editor.getCaretPosition());
}
我在退格上有问题.我已经试过了
if (e.getKeyChar() == KeyEvent.VK_BACK_SPACE) {
editor.insert("\b", editor.getCaretPosition());
}
当按下退格键时,这似乎增加了一个很小的空间.它不像空格那么大,按一次几乎不明显.绝对不是退格.更糟糕的是,我将必须复制所有字符直到插入符号的位置-1并将它们附加到插入符号位置之后的所有字符,但是我不喜欢这种解决方案.
解决方法:
使用键绑定使空格键和退格键具有关联的操作,然后如果按下了退格键,则从JTextArea的Document中删除一个字符.
例如,
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import javax.swing.*;
import javax.swing.text.BadLocationException;
import javax.swing.text.PlainDocument;
@SuppressWarnings("serial")
public class TextAreaFun extends JPanel {
public static final String SPACE = "space";
public static final String BACK_SPACE = "back space";
private JTextArea textArea = new JTextArea(15, 50);
public TextAreaFun() {
// create our key bindings
// only allow key presses to initiate an action if the JTextArea has focus
int condition = JComponent.WHEN_FOCUSED;
InputMap taInputMap = textArea.getInputMap(condition);
ActionMap taActionMap = textArea.getActionMap();
taInputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_SPACE, 0), SPACE);
taInputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_BACK_SPACE, 0),
BACK_SPACE);
taActionMap.put(SPACE, new KeyAction(textArea, SPACE));
taActionMap.put(BACK_SPACE, new KeyAction(textArea, BACK_SPACE));
// checkbox that stops all editing except for that specified in the
// key bindings above
JCheckBox chkBox = new JCheckBox(new AbstractAction("Prevent Editing") {
{
putValue(SELECTED_KEY, Boolean.FALSE); // default to unchecked
putValue(MNEMONIC_KEY, KeyEvent.VK_P);
}
@Override
public void actionPerformed(ActionEvent evt) {
boolean selection = (Boolean) getValue(SELECTED_KEY);
textArea.setEditable(!selection);
}
});
JPanel bottomPanel = new JPanel();
bottomPanel.add(chkBox);
setLayout(new BoxLayout(this, BoxLayout.PAGE_AXIS));
add(new JScrollPane(textArea));
add(Box.createVerticalStrut(10));
add(bottomPanel);
}
private static void createAndShowGui() {
TextAreaFun mainPanel = new TextAreaFun();
JFrame frame = new JFrame("TextAreaFun");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
@SuppressWarnings("serial")
// action to be initiated by key bindings
class KeyAction extends AbstractAction {
private PlainDocument textAreaDocument;
private String title;
public KeyAction(JTextArea textArea, String title) {
this.textAreaDocument = (PlainDocument) textArea.getDocument();
this.title = title;
}
@Override
public void actionPerformed(ActionEvent e) {
if (title.equals(TextAreaFun.SPACE)) {
try {
textAreaDocument.insertString(textAreaDocument.getLength(), " ",
null);
} catch (BadLocationException e1) {
e1.printStackTrace();
}
} else if (title.equals(TextAreaFun.BACK_SPACE)) {
if (textAreaDocument.getLength() == 0) {
return;
}
try {
textAreaDocument.remove(textAreaDocument.getLength() - 1, 1);
} catch (BadLocationException e1) {
e1.printStackTrace();
}
}
}
}
标签:jtextarea,swing,key-bindings,backspace,java
来源: https://codeday.me/bug/20191201/2080753.html
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