java 向 JTextfield 添加提示文本属性
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Adding a prompt text property to JTextfield
提问by Jayashri
I am using Netbeans IDE. I want to give the prompt text to JTextfieldin such a way that when user enters the text into JTextFieldit gets cleared and accepts the users input.
我正在使用 Netbeans IDE。我想以JTextfield这样一种方式提供提示文本，当用户输入文本时，JTextField它会被清除并接受用户输入。
采纳答案by David Kroukamp
You can add a simple focus listener to your textfield, and validate the data of the textfield when focus is Lost something like this:
您可以向文本字段添加一个简单的焦点侦听器，并在失去焦点时验证文本字段的数据，如下所示：
import java.awt.EventQueue;
import java.awt.GridLayout;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JTextField;
/**
*
* @author David
*/
public class Test extends JFrame {
private JTextField textField, textField2;
public Test() {
createAndShowUI();
}
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
Test test = new Test();
}
});
}
private void createAndShowUI() {
setTitle("Test");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
createComponents();
addComponentsToContentPane();
addListeners();
pack();
setVisible(true);
}
private void addComponentsToContentPane() {
getContentPane().setLayout(new GridLayout(2, 1));
getContentPane().add(textField);
getContentPane().add(textField2);
}
private void createComponents() {
textField = new JTextField(10);
textField2 = new JTextField("Click here to lose focus of above textField");
}
private void addListeners() {
textField.addFocusListener(new FocusListener() {
@Override
public void focusGained(FocusEvent fe) {
}
@Override
public void focusLost(FocusEvent fe) {
if (textField.getText().length() >=1) {
JOptionPane.showMessageDialog(null, "You entered valid data");
textField.setText("");
}else {
JOptionPane.showMessageDialog(null, "You entered invalid data");
textField.grabFocus();//make the textField in foucs again
}
}
});
}
}
To do this in NetBeans right click on the Component, select Events->Focus->focusLost.
为此，在 NetBeans 中右键单击Component，选择Events-> Focus-> focusLost。
回答by user3033626
I don't know what propt-text-fields David Kroukamp already saw, but with the following code I created those textFields who I know ;)
我不知道 David Kroukamp 已经看到了什么 propt-text-fields，但是使用以下代码我创建了我认识的那些 textFields ;)
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;
import javax.swing.JTextField;
public class PTextField extends JTextField {
public PTextField(final String proptText) {
super(proptText);
addFocusListener(new FocusListener() {
@Override
public void focusLost(FocusEvent e) {
if(getText().isEmpty()) {
setText(proptText);
}
}
@Override
public void focusGained(FocusEvent e) {
if(getText().equals(proptText)) {
setText("");
}
}
});
}
}
