带有输入提示的 Java JTextField

Java JTextField with input hint

提问by Wienczny

I would like to add a hint value to my javax.swing.JTextField. It should look like Firefox rendering of <input type="text" title="bla">. This creates an edit field with the text 'bla' in the background. If the textbox has focus the title-text disappears and just reappears if the user leaves the editbox without text.

我想向我的javax.swing.JTextField. 它应该看起来像 Firefox 呈现的<input type="text" title="bla">. 这会在背景中创建一个带有文本“bla”的编辑字段。如果文本框具有焦点，则标题文本会消失，如果用户离开没有文本的编辑框，则只会重新出现。

Is there a (free) swing component that does something like this?

是否有（免费）摆动组件可以执行此类操作？

采纳答案by Dmitry

Take a look at this one: http://code.google.com/p/xswingx/

看看这个：http: //code.google.com/p/xswingx/

It is not very difficult to implement it by yourself, btw. A couple of listeners and custom renderer and voila.

自己实现它并不是很难，顺便说一句。几个监听器和自定义渲染器，瞧。

回答by Matt

For any Swing component (that is, anything that extends JComponent), you can call the setToolTipText(String) method.

对于任何 Swing 组件（即任何扩展 JComponent 的组件），您都可以调用 setToolTipText(String) 方法。

For more information, reference the following links:

有关更多信息，请参考以下链接：

• API Documentation for setToolTipText
• "How to Use Tool Tips" tutorial

• setToolTipText 的 API 文档
• “如何使用工具提示”教程

回答by Bart Kiers

You could create your own:

您可以创建自己的：

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;
import javax.swing.*;

public class Main {

  public static void main(String[] args) {

    final JFrame frame = new JFrame();

    frame.setLayout(new BorderLayout());

    final JTextField textFieldA = new HintTextField("A hint here");
    final JTextField textFieldB = new HintTextField("Another hint here");

    frame.add(textFieldA, BorderLayout.NORTH);
    frame.add(textFieldB, BorderLayout.CENTER);
    JButton btnGetText = new JButton("Get text");

    btnGetText.addActionListener(new ActionListener() {
      @Override
      public void actionPerformed(ActionEvent e) {
        String message = String.format("textFieldA='%s', textFieldB='%s'",
            textFieldA.getText(), textFieldB.getText());
        JOptionPane.showMessageDialog(frame, message);
      }
    });

    frame.add(btnGetText, BorderLayout.SOUTH);
    frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    frame.setVisible(true);
    frame.pack();
  }
}

class HintTextField extends JTextField implements FocusListener {

  private final String hint;
  private boolean showingHint;

  public HintTextField(final String hint) {
    super(hint);
    this.hint = hint;
    this.showingHint = true;
    super.addFocusListener(this);
  }

  @Override
  public void focusGained(FocusEvent e) {
    if(this.getText().isEmpty()) {
      super.setText("");
      showingHint = false;
    }
  }
  @Override
  public void focusLost(FocusEvent e) {
    if(this.getText().isEmpty()) {
      super.setText(hint);
      showingHint = true;
    }
  }

  @Override
  public String getText() {
    return showingHint ? "" : super.getText();
  }
}

If you're still on Java 1.5, replace the this.getText().isEmpty()with this.getText().length() == 0.

如果你仍然在Java 1.5中，替换this.getText().isEmpty()用this.getText().length() == 0。

回答by culmat

Here is a single class copy/paste solution:

这是一个单类复制/粘贴解决方案：

import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;

import javax.swing.plaf.basic.BasicTextFieldUI;
import javax.swing.text.JTextComponent;


public class HintTextFieldUI extends BasicTextFieldUI implements FocusListener {

    private String hint;
    private boolean hideOnFocus;
    private Color color;

    public Color getColor() {
        return color;
    }

    public void setColor(Color color) {
        this.color = color;
        repaint();
    }

    private void repaint() {
        if(getComponent() != null) {
            getComponent().repaint();           
        }
    }

    public boolean isHideOnFocus() {
        return hideOnFocus;
    }

    public void setHideOnFocus(boolean hideOnFocus) {
        this.hideOnFocus = hideOnFocus;
        repaint();
    }

    public String getHint() {
        return hint;
    }

    public void setHint(String hint) {
        this.hint = hint;
        repaint();
    }
    public HintTextFieldUI(String hint) {
        this(hint,false);
    }

    public HintTextFieldUI(String hint, boolean hideOnFocus) {
        this(hint,hideOnFocus, null);
    }

    public HintTextFieldUI(String hint, boolean hideOnFocus, Color color) {
        this.hint = hint;
        this.hideOnFocus = hideOnFocus;
        this.color = color;
    }

    @Override
    protected void paintSafely(Graphics g) {
        super.paintSafely(g);
        JTextComponent comp = getComponent();
        if(hint!=null && comp.getText().length() == 0 && (!(hideOnFocus && comp.hasFocus()))){
            if(color != null) {
                g.setColor(color);
            } else {
                g.setColor(comp.getForeground().brighter().brighter().brighter());              
            }
            int padding = (comp.getHeight() - comp.getFont().getSize())/2;
            g.drawString(hint, 2, comp.getHeight()-padding-1);          
        }
    }

    @Override
    public void focusGained(FocusEvent e) {
        if(hideOnFocus) repaint();

    }

    @Override
    public void focusLost(FocusEvent e) {
        if(hideOnFocus) repaint();
    }
    @Override
    protected void installListeners() {
        super.installListeners();
        getComponent().addFocusListener(this);
    }
    @Override
    protected void uninstallListeners() {
        super.uninstallListeners();
        getComponent().removeFocusListener(this);
    }
}

Use it like this:

像这样使用它：

TextField field = new JTextField();
field.setUI(new HintTextFieldUI("Search", true));

Note that it is happening in protected void paintSafely(Graphics g).

请注意，它发生在protected void paintSafely(Graphics g).

回答by user814168

If you still look for a solution, here's one that combined other answers (Bart Kiers and culmat) for your reference:

如果您仍在寻找解决方案，这里有一个结合了其他答案（Bart Kiers 和 culmat）供您参考：

import javax.swing.*;
import javax.swing.text.JTextComponent;
import java.awt.*;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;


public class HintTextField extends JTextField implements FocusListener
{

    private String hint;

    public HintTextField ()
    {
        this("");
    }

    public HintTextField(final String hint)
    {
        setHint(hint);
        super.addFocusListener(this);
    }

    public void setHint(String hint)
    {
        this.hint = hint;
        setUI(new HintTextFieldUI(hint, true));
        //setText(this.hint);
    }


    public void focusGained(FocusEvent e)
    {
        if(this.getText().length() == 0)
        {
            super.setText("");
        }
    }

    public void focusLost(FocusEvent e)
    {
        if(this.getText().length() == 0)
        {
            setHint(hint);
        }
    }

    public String getText()
    {
        String typed = super.getText();
        return typed.equals(hint)?"":typed;
    }
}

class HintTextFieldUI extends javax.swing.plaf.basic.BasicTextFieldUI implements FocusListener
{

    private String hint;
    private boolean hideOnFocus;
    private Color color;

    public Color getColor()
    {
        return color;
    }

    public void setColor(Color color)
    {
        this.color = color;
        repaint();
    }

    private void repaint()
    {
        if(getComponent() != null)
        {
            getComponent().repaint();
        }
    }

    public boolean isHideOnFocus()
    {
        return hideOnFocus;
    }

    public void setHideOnFocus(boolean hideOnFocus)
    {
        this.hideOnFocus = hideOnFocus;
        repaint();
    }

    public String getHint()
    {
        return hint;
    }

    public void setHint(String hint)
    {
        this.hint = hint;
        repaint();
    }

    public HintTextFieldUI(String hint)
    {
        this(hint, false);
    }

    public HintTextFieldUI(String hint, boolean hideOnFocus)
    {
        this(hint, hideOnFocus, null);
    }

    public HintTextFieldUI(String hint, boolean hideOnFocus, Color color)
    {
        this.hint = hint;
        this.hideOnFocus = hideOnFocus;
        this.color = color;
    }


    protected void paintSafely(Graphics g)
    {
        super.paintSafely(g);
        JTextComponent comp = getComponent();
        if(hint != null && comp.getText().length() == 0 && (!(hideOnFocus && comp.hasFocus())))
        {
            if(color != null)
            {
                g.setColor(color);
            }
            else
            {
                g.setColor(Color.gray);
            }
            int padding = (comp.getHeight() - comp.getFont().getSize()) / 2;
            g.drawString(hint, 5, comp.getHeight() - padding - 1);
        }
    }


    public void focusGained(FocusEvent e)
    {
        if(hideOnFocus) repaint();

    }


    public void focusLost(FocusEvent e)
    {
        if(hideOnFocus) repaint();
    }

    protected void installListeners()
    {
        super.installListeners();
        getComponent().addFocusListener(this);
    }

    protected void uninstallListeners()
    {
        super.uninstallListeners();
        getComponent().removeFocusListener(this);
    }
}



Usage:
HintTextField field = new HintTextField();
field.setHint("Here's a hint");

回答by Adam Gawne-Cain

Here is a simple way that looks good in any L&F:

这是一种在任何 L&F 中看起来都不错的简单方法：

public class HintTextField extends JTextField {
    public HintTextField(String hint) {
        _hint = hint;
    }
    @Override
    public void paint(Graphics g) {
        super.paint(g);
        if (getText().length() == 0) {
            int h = getHeight();
            ((Graphics2D)g).setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING,RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
            Insets ins = getInsets();
            FontMetrics fm = g.getFontMetrics();
            int c0 = getBackground().getRGB();
            int c1 = getForeground().getRGB();
            int m = 0xfefefefe;
            int c2 = ((c0 & m) >>> 1) + ((c1 & m) >>> 1);
            g.setColor(new Color(c2, true));
            g.drawString(_hint, ins.left, h / 2 + fm.getAscent() / 2 - 2);
        }
    }
    private final String _hint;
}

回答by user2473015

Have look at WebLookAndFeel at https://github.com/mgarin/weblaf/

在https://github.com/mgarin/weblaf/查看 WebLookAndFeel

WebTextField txtName = new com.alee.laf.text.WebTextField();

txtName.setHideInputPromptOnFocus(false);

txtName.setInputPrompt("Name");

txtName.setInputPromptFont(new java.awt.Font("Ubuntu", 0, 18));

txtName.setInputPromptForeground(new java.awt.Color(102, 102, 102));

txtName.setInputPromptPosition(0);

回答by Shivam Rajput

This can be achieved by using a focus listener to update the text field content.

这可以通过使用焦点侦听器更新文本字段内容来实现。

Make the class implement the focus listener interface:

使类实现焦点侦听器接口：

class YourClass implements FocusListener

Add a method to catch when focus is gained that blanks the field:

添加一个方法来捕捉获得焦点时使字段空白：

public void focusGained(FocusEvent e) {
    if(JTextField1.getText().equals("Username")) {
        JTextField1.setText("");
    }
}

Add a method to catch when focus is lost to redisplay the default entry if the field was blank:

添加一个在失去焦点时捕获的方法，以在字段为空时重新显示默认条目：

public void focusLost(FocusEvent e) {
    if(JTextField1.getText().equals("")) {
        JTextField1.setText("Username");
        // you should prevent the form from being processed in this state
        // as it will literally contain "Username" for the username
    }
}

Register your class as the focus listener for text field:

将您的类注册为文本字段的焦点侦听器：

textField.addFocusListener(this);

Learn more at How to Write a Focus Listenerin the Java Tutorials.

在 Java 教程中的如何编写焦点侦听器中了解更多信息。

回答by Dave The Dane

Here is a fully working example based on Adam Gawne-Cain's earlier Posting. His solution is simple and actually works exceptionally well.

这是一个基于 Adam Gawne-Cain 早期发布的完整示例。他的解决方案很简单，实际上效果非常好。

I've used the following text in a Grid of multiple Fields:

我在多个字段的网格中使用了以下文本：

H__|__WWW__+__XXXX__+__WWW__|__H

this makes it possible to easily verify the x/y alignment of the hinted text.

这使得可以轻松验证提示文本的 x/y 对齐。

A couple of observations:
- there are any number of solutions out there, but many only work superficially and/or are buggy
- sun.tools.jconsole.ThreadTab.PromptingTextField is a simple solution, but it only shows the prompting text when the Field doesn't have the focus & it's private, but nothing a little cut-and-paste won't fix.

一些观察：
- 有许多解决方案，但许多只能在表面上工作和/或有问题
- sun.tools.jconsole.ThreadTab.PromptingTextField 是一个简单的解决方案，但它只在字段时显示提示文本没有焦点并且它是私密的，但是一点点剪切和粘贴都无法解决问题。

The following works on JDK 8 and upwards:

以下适用于 JDK 8 及更高版本：

import java.awt.*;
import java.util.stream.*;
import javax.swing.*;
/**
 * @author DaveTheDane, based on a suggestion from Adam Gawne-Cain
 */
public final class JTextFieldPromptExample extends JFrame {

    private static JTextField newPromptedJTextField (final String text, final String prompt) {

        final String promptPossiblyNullButNeverWhitespace = prompt == null || prompt.trim().isEmpty()  ?  null  :  prompt;

        return new JTextField(text) {
            @Override
            public void paintComponent(final Graphics    USE_g2d_INSTEAD) {
                final Graphics2D     g2d =  (Graphics2D) USE_g2d_INSTEAD;

                super.paintComponent(g2d);

//              System.out.println("Paint.: " + g2d);

                if (getText().isEmpty()
                &&  promptPossiblyNullButNeverWhitespace != null) {
                    g2d.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);

                    final Insets      ins = getInsets();
                    final FontMetrics fm  = g2d.getFontMetrics();

                    final int cB = getBackground().getRGB();
                    final int cF = getForeground().getRGB();
                    final int m  = 0xfefefefe;
                    final int c2 = ((cB & m) >>> 1) + ((cF & m) >>> 1); // "for X in (A, R, G, B) {Xnew = (Xb + Xf) / 2}"
                    /*
                     * The hint text color should be halfway between the foreground and background colors so it is always gently visible.
                     * The variables c0,c1,m,c2 calculate the halfway color's ARGB fields simultaneously without overflowing 8 bits.
                     * Swing sets the Graphics' font to match the JTextField's font property before calling the "paint" method,
                     * so the hint font will match the JTextField's font.
                     * Don't think there are any side effects because Swing discards the Graphics after painting.
                     * Adam Gawne-Cain, Aug 6 2019 at 15:55
                     */
                    g2d.setColor(new Color(c2, true));
                    g2d.drawString(promptPossiblyNullButNeverWhitespace, ins.left, getHeight() - fm.getDescent() - ins.bottom);
                    /*
                     * y Coordinate based on Descent & Bottom-inset seems to align Text spot-on.
                     * DaveTheDane, Apr 10 2020
                     */
                }
            }
        };
    }

    private static final GridBagConstraints GBC_LEFT  = new GridBagConstraints();
    private static final GridBagConstraints GBC_RIGHT = new GridBagConstraints();
    /**/    static {
        GBC_LEFT .anchor    = GridBagConstraints.LINE_START;
        GBC_LEFT .fill      = GridBagConstraints.HORIZONTAL;
        GBC_LEFT .insets    = new Insets(8, 8, 0, 0);

        GBC_RIGHT.gridwidth = GridBagConstraints.REMAINDER;
        GBC_RIGHT.fill      = GridBagConstraints.HORIZONTAL;
        GBC_RIGHT.insets    = new Insets(8, 8, 0, 8);
    }

    private <C extends Component> C addLeft (final C component) {
        this    .add           (component);
        this.gbl.setConstraints(component, GBC_LEFT);
        return                  component;
    }
    private <C extends Component> C addRight(final C component) {
        this    .add           (component);
        this.gbl.setConstraints(component, GBC_RIGHT);
        return                  component;
    }

    private static final String ALIGN = "H__|__WWW__+__XXXX__+__WWW__|__H";

    private final GridBagLayout gbl = new GridBagLayout();

    public JTextFieldPromptExample(final String title) {
        super(title);
        this.setLayout(gbl);

        final java.util.List<JTextField> texts = Stream.of(
                addLeft (newPromptedJTextField(ALIGN + ' ' + "Top-Left"    , ALIGN)),
                addRight(newPromptedJTextField(ALIGN + ' ' + "Top-Right"   , ALIGN)),

                addLeft (newPromptedJTextField(ALIGN + ' ' + "Middle-Left" , ALIGN)),
                addRight(newPromptedJTextField(                       null , ALIGN)),

                addLeft (new        JTextField("x"        )),
                addRight(newPromptedJTextField("x",   ""  )),

                addLeft (new        JTextField(null       )),
                addRight(newPromptedJTextField(null,  null)),

                addLeft (newPromptedJTextField(ALIGN + ' ' + "Bottom-Left" , ALIGN)),
                addRight(newPromptedJTextField(ALIGN + ' ' + "Bottom-Right", ALIGN)) ).collect(Collectors.toList());

        final JButton button = addRight(new JButton("Get texts"));
        /**/                   addRight(Box.createVerticalStrut(0)); // 1 last time forces bottom inset

        this.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        this.setPreferredSize(new Dimension(740, 260));
        this.pack();
        this.setResizable(false);
        this.setVisible(true);

        button.addActionListener(e -> {
            texts.forEach(text -> System.out.println("Text..: " + text.getText()));
        });
    }

    public static void main(final String[] args) {
        SwingUtilities.invokeLater(() -> new JTextFieldPromptExample("JTextField with Prompt"));
    }
}