java swing JTextField设置占位符

Question

我创建了一个JTextField，现在我想在JTextField上设置占位符，但我不知道怎么做?请帮助。下面是我的代码:

JTextField database=new JTextField("Enter Data Base Name");
database.setPreferredSize(database.getPreferredSize());
database.setText("");

Answer 1

试试这个类:

package playground;
import java.awt.*;
import javax.swing.*;
import javax.swing.text.Document;
@SuppressWarnings("serial")
public class PlaceholderTextField extends JTextField {
    public static void main(final String[] args) {
        final PlaceholderTextField tf = new PlaceholderTextField("");
        tf.setColumns(20);
        tf.setPlaceholder("All your base are belong to us!");
        final Font f = tf.getFont();
        tf.setFont(new Font(f.getName(), f.getStyle(), 30));
        JOptionPane.showMessageDialog(null, tf);
    }
    private String placeholder;
    public PlaceholderTextField() {
    }
    public PlaceholderTextField(
        final Document pDoc,
        final String pText,
        final int pColumns)
    {
        super(pDoc, pText, pColumns);
    }
    public PlaceholderTextField(final int pColumns) {
        super(pColumns);
    }
    public PlaceholderTextField(final String pText) {
        super(pText);
    }
    public PlaceholderTextField(final String pText, final int pColumns) {
        super(pText, pColumns);
    }
    public String getPlaceholder() {
        return placeholder;
    }
    @Override
    protected void paintComponent(final Graphics pG) {
        super.paintComponent(pG);
        if (placeholder == null || placeholder.length() == 0 || getText().length() > 0) {
            return;
        }
        final Graphics2D g = (Graphics2D) pG;
        g.setRenderingHint(
            RenderingHints.KEY_ANTIALIASING,
            RenderingHints.VALUE_ANTIALIAS_ON);
        g.setColor(getDisabledTextColor());
        g.drawString(placeholder, getInsets().left, pG.getFontMetrics()
            .getMaxAscent() + getInsets().top);
    }
    public void setPlaceholder(final String s) {
        placeholder = s;
    }
}

Answer 2

JTextField searchText;

…在构造函数:

searchText = new JTextField("Search");
searchText.setForeground(Color.GRAY);
searchText.addFocusListener(new FocusListener() {
    @Override
    public void focusGained(FocusEvent e) {
        if (searchText.getText().equals("Search")) {
            searchText.setText("");
            searchText.setForeground(Color.BLACK);
        }
    }
    @Override
    public void focusLost(FocusEvent e) {
        if (searchText.getText().isEmpty()) {
            searchText.setForeground(Color.GRAY);
            searchText.setText("Search");
        }
    }
    });

Answer 3

所以简单地使用swingx jar然后像这样

JTextArea txtMSISDNList = new JTextArea();  
PromptSupport.setPrompt("01197585960,01197585961", txtMSISDNList);

Answer 4

如果我没理解错的话，文本提示显示了一种方法。