本文介绍了java swing JTextField 设置PlaceHolder的处理方法，对大家解决问题具有一定的参考价值
问题描述
我创建了一个 JTextField，现在我想在该 JTextField 上设置占位符，但我不知道如何设置?请帮忙.这是我的代码:
I created a JTextField and now I want to set the placeholder on that JTextField, but I don't know how? Please help. Here is my code:
JTextField database=new JTextField("Enter Data Base Name");
database.setPreferredSize(database.getPreferredSize());
database.setText("");
推荐答案
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;
}
}
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