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带有输入提示的Java JTextField

java swing input

带有输入提示的Java JTextField,java,swing,input,jtextfield,hint,Java,Swing,Input,Jtextfield,Hint,我想在javax.swing.JTextField中添加一个提示值。它应该看起来像Firefox对的渲染。这将创建一个文本为“bla”的编辑字段。如果文本框具有焦点，则标题文本将消失，如果用户离开编辑框而没有文本，则标题文本将重新出现 有这样的（自由）swing组件吗？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 有关更多信息，请参考以下链接： 看看这个： 顺便说一句，您自己实现它并不困难。几个侦听器和自定义渲

我想在javax.swing.JTextField中添加一个提示值。它应该看起来像Firefox对
的渲染。这将创建一个文本为“bla”的编辑字段。如果文本框具有焦点，则标题文本将消失，如果用户离开编辑框而没有文本，则标题文本将重新出现

有这样的（自由）swing组件吗？

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

有关更多信息，请参考以下链接：

看看这个：

顺便说一句，您自己实现它并不困难。几个侦听器和自定义渲染器以及瞧。

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();
  }
}
如果您仍然使用Java 1.5，请将
this.getText（）.isEmpty（）
替换为
this.getText（）.length（）==0

以下是一个单类复制/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);
    }
}
像这样使用它：

TextField field = new JTextField();
field.setUI(new HintTextFieldUI("Search", true));
请注意，它发生在
受保护的虚空油漆安全（图形g）

中，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）的解决方案供您参考：

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");
以下是一种在任何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;
}
看看网页，感受一下

这可以通过使用焦点侦听器来更新文本字段内容来实现

使类实现焦点侦听器接口：

class YourClass实现了FocusListener
添加一个方法，以便在获得焦点时捕捉空白字段：

public void focus获得（FocusEvent e）{
if（JTextField1.getText（）.equals（“用户名”））{
JTextField1.setText（“”）；
}
}
添加一个方法，以便在焦点丢失时捕获，以便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（“用户名”）；
//应防止在此状态下处理表单
//因为它将字面上包含用户名的“Username”
}
}
将类注册为文本字段的焦点侦听器：

textField.addFocusListener(this);
在Java教程中了解更多信息。

这里是一个基于Adam Gawne Cain先前帖子的完整示例。他的解决方案很简单，实际上效果非常好

我在多个字段的网格中使用了以下文本：

H__|__WWW__+__XXXX__+__WWW__|__H
这使得可以轻松验证提示文本的x/y对齐方式

几个观察结果：
-有很多解决方案，但其中许多只是表面上的和/或有缺陷
-sun.tools.jconsole.ThreadTab.PromptingTextField是一个简单的解决方案，但它仅在字段没有焦点时显示提示文本&它是私有的，但任何一点剪切和粘贴都无法修复

以下是JDK 8及以上版本的工作：

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"));
    }
}

import java.awt.*；
导入java.util.stream.*；
导入javax.swing.*；
/**
*@作者Davethesdane，根据Adam Gawne Cain的建议
*/
公共最终类JTextFieldPromptExample扩展了JFrame{
私有静态JTextField newPromptedJTextField（最终字符串文本，最终字符串提示）{
最后一个字符串promptPossiblyNullButNeverWhitespace=prompt==null | | prompt.trim（）.isEmpty（）？null:prompt；
返回新的JTextField（文本）{
@凌驾
公共虚空绘制组件（最终图形使用_g2d_）{
最终图形2d g2d=（图形2d）改用_g2d_；
超级油漆组件（g2d）；
//系统输出打印项次（“油漆：”+g2d）；
if（getText（）.isEmpty（））
&&promptPossiblyNullButNeverWhitespace！=null）{
g2d.setRenderingHint（renderingHits.KEY\u TEXT\u ANTIALIAS，renderingHits.VALUE\u TEXT\u ANTIALIAS\u ON）；
最终插入ins=getInsets（）；
final FontMetrics fm=g2d.getFontMetrics（）；
final int cB=getBackground（）.getRGB（）；
final int cF=get前台（）.getRGB（）；
最终整数m=0xfefe；
最终整数c2=（（cB&m）>>>1）+（（cF&m）>>>1）；/“对于（A，R，G，B）中的X，{Xnew=（Xb+Xf）/2}”
/*
*提示文本颜色应介于前景色和背景色之间，以便始终柔和可见。
*变量c0、c1、m、c2在不溢出8位的情况下同时计算中间色的ARGB字段。
*Swing在调用“paint”方法之前，将图形的字体设置为与JTextField的字体属性相匹配，
*因此提示字体将与JTextField的字体匹配。
*不要认为有任何副作用，因为Swing会在绘制后丢弃图形。
*亚当·加恩·凯恩，2019年8月6日15:55
*/
g2d.setColor（新颜色（c2，真））；
g2d.drawString（promptPossiblyNullButNeverWhitespace，ins.left，getHeight（）-fm.getDescent（）-ins.bottom）；
/*
*基于下降和底部插入的y坐标似乎与文本点对齐。
*达维瑟丹，2020年4月10日
*/
}
}
};
}
私有静态最终GridBagConstraints GBC_LEFT=新GridBagConstraints（）；
私有静态最终GridBagConstraints GBC_RIGHT=新GridBagConstraints（）；
/**/静止的{
GBC_LEFT.anchor=GridBagConstraints.LINE_START；
GBC_LEFT.fill=GridBagConstraints.HORIZONTAL；
GBC_左。插图=新插图（8,8,0,0）；
GBC_RIGHT.gridwidth=GridBagConstraints.rements；
GBC_RIGHT.fill=GridBagConstraints.HORIZONTAL；
GBC_RIGHT.insets=新的插图（8,8,0,8

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"));
    }
}