如何将图标转换为图像
Posted
技术标签:
【中文标题】如何将图标转换为图像【英文标题】：How can I convert an Icon to an Image 【发布时间】：2011-08-15 09:22:06 【问题描述】：我正在尝试使用此代码将图标 (javax.swing.Icon) 转换为图像 (java.awt.Image)：
private Image iconToImage(Icon icon)
if(icon instanceof ImageIcon)
return ((ImageIcon) icon).getImage();
else
BufferedImage image = new BufferedImage(icon.getIconWidth(), icon.getIconHeight(), BufferedImage.TYPE_INT_RGB);
icon.paintIcon(null, image.getGraphics(), 0, 0);
return image;
问题是，paintIcon 函数会在 image.getGraphics() 上抛出一个 NullPointerException。
为了记录，icon 值是默认的CheckBox 图标（通过UIManager.getIcon("CheckBox.icon") 获得）
这里是抛出异常的详细信息：
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at com.sun.java.swing.plaf.windows.WindowsIconFactory$CheckBoxIcon.paintIcon(WindowsIconFactory.java:306)
at utils.WarningRenderer.iconToImage(WarningRenderer.java:50)
at utils.WarningRenderer.<init>(WarningRenderer.java:38)
at deliveryexpress.DeliveryExpressView.setWarnings(DeliveryExpressView.java:278)
at deliveryexpress.DeliveryExpressView.updateLists(DeliveryExpressView.java:218)
at deliveryexpress.DeliveryExpressView.access$1100(DeliveryExpressView.java:47)
at deliveryexpress.DeliveryExpressView$5.addCheck(DeliveryExpressView.java:183)
at org.japura.gui.model.DefaultListCheckModel.fireCheckListModelListeners(Unknown Source)
at org.japura.gui.model.DefaultListCheckModel.fireAddCheckListModelListeners(Unknown Source)
at org.japura.gui.model.DefaultListCheckModel.addCheck(Unknown Source)
at org.japura.gui.CheckList$1.mouseClicked(Unknown Source)
at java.awt.AWTEventMulticaster.mouseClicked(AWTEventMulticaster.java:253)
at java.awt.Component.processMouseEvent(Component.java:6292)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3267)
at java.awt.Component.processEvent(Component.java:6054)
at java.awt.Container.processEvent(Container.java:2041)
at java.awt.Component.dispatchEventImpl(Component.java:4652)
at java.awt.Container.dispatchEventImpl(Container.java:2099)
at java.awt.Component.dispatchEvent(Component.java:4482)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4577)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4247)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4168)
at java.awt.Container.dispatchEventImpl(Container.java:2085)
at java.awt.Window.dispatchEventImpl(Window.java:2478)
at java.awt.Component.dispatchEvent(Component.java:4482)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:644)
at java.awt.EventQueue.access$000(EventQueue.java:85)
at java.awt.EventQueue$1.run(EventQueue.java:603)
at java.awt.EventQueue$1.run(EventQueue.java:601)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:98)
at java.awt.EventQueue$2.run(EventQueue.java:617)
at java.awt.EventQueue$2.run(EventQueue.java:615)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:614)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
如果您需要更多详细信息，请告诉我，我会编辑我的帖子以添加它们。
谢谢！
【问题讨论】：
完美的问题，给出了所有必要的细节:-) 【参考方案1】：刚刚找到了一个代码 sn-p，如果您想更频繁地包装那些行为不端的 LAF 提供的图标，它可能会有所帮助：
/**
* Some ui-icons misbehave in that they unconditionally class-cast to the
* component type they are mostly painted on. Consequently they blow up if
* we are trying to paint them anywhere else (f.i. in a renderer).
*
* This Icon is an adaption of a cool trick by Darryl Burke/Rob Camick found at
* http://tips4java.wordpress.com/2008/12/18/icon-table-cell-renderer/#comment-120
*
* The base idea is to instantiate a component of the type expected by the icon,
* let it paint into the graphics of a bufferedImage and create an ImageIcon from it.
* In subsequent calls the ImageIcon is used.
*
*/
public static class SafeIcon implements Icon
private Icon wrappee;
private Icon standIn;
public SafeIcon(Icon wrappee)
this.wrappee = wrappee;
@Override
public int getIconHeight()
return wrappee.getIconHeight();
@Override
public int getIconWidth()
return wrappee.getIconWidth();
@Override
public void paintIcon(Component c, Graphics g, int x, int y)
if (standIn == this)
paintFallback(c, g, x, y);
else if (standIn != null)
standIn.paintIcon(c, g, x, y);
else
try
wrappee.paintIcon(c, g, x, y);
catch (ClassCastException e)
createStandIn(e, x, y);
standIn.paintIcon(c, g, x, y);
/**
* @param e
*/
private void createStandIn(ClassCastException e, int x, int y)
try
Class<?> clazz = getClass(e);
JComponent standInComponent = getSubstitute(clazz);
standIn = createImageIcon(standInComponent, x, y);
catch (Exception e1)
// something went wrong - fallback to this painting
standIn = this;
private Icon createImageIcon(JComponent standInComponent, int x, int y)
BufferedImage image = new BufferedImage(getIconWidth(),
getIconHeight(), BufferedImage.TYPE_INT_ARGB);
Graphics g = image.createGraphics();
try
wrappee.paintIcon(standInComponent, g, 0, 0);
return new ImageIcon(image);
finally
g.dispose();
/**
* @param clazz
* @throws IllegalAccessException
*/
private JComponent getSubstitute(Class<?> clazz) throws IllegalAccessException
JComponent standInComponent;
try
standInComponent = (JComponent) clazz.newInstance();
catch (InstantiationException e)
standInComponent = new AbstractButton()
;
((AbstractButton) standInComponent).setModel(new DefaultButtonModel());
return standInComponent;
private Class<?> getClass(ClassCastException e) throws ClassNotFoundException
String className = e.getMessage();
className = className.substring(className.lastIndexOf(" ") + 1);
return Class.forName(className);
private void paintFallback(Component c, Graphics g, int x, int y)
g.drawRect(x, y, getIconWidth(), getIconHeight());
g.drawLine(x, y, x + getIconWidth(), y + getIconHeight());
g.drawLine(x + getIconWidth(), y, x, y + getIconHeight());
要在您的 sn-p 中使用，只需传入任意组件：
icon = new SafeIcon(icon);
BufferedImage image = new BufferedImage(icon.getIconWidth(), icon.getIconHeight(), BufferedImage.TYPE_INT_RGB);
icon.paintIcon(new JPanel(), image.getGraphics(), 0, 0);
【讨论】：
谢谢，成功了！它不包括 alpha，但我会尝试自己解决这个问题：p @oliholz 可能遗漏了一些东西，但是使用支持 alpha 的类型（如 TYPE_INT_ARGB）创建 BufferedImage 有什么问题？【参考方案2】：试试这个：
static Image iconToImage(Icon icon)
if (icon instanceof ImageIcon)
return ((ImageIcon)icon).getImage();
else
int w = icon.getIconWidth();
int h = icon.getIconHeight();
GraphicsEnvironment ge =
GraphicsEnvironment.getLocalGraphicsEnvironment();
GraphicsDevice gd = ge.getDefaultScreenDevice();
GraphicsConfiguration gc = gd.getDefaultConfiguration();
BufferedImage image = gc.createCompatibleImage(w, h);
Graphics2D g = image.createGraphics();
icon.paintIcon(null, g, 0, 0);
g.dispose();
return image;
一个完整的示例，我们将 laf 提供的图标转换为图像并将其用于 Windows 系统托盘。
import java.awt.*;
import java.awt.image.*;
import java.awt.event.*;
import javax.swing.*;
public class SysTrayDemo
protected static TrayIcon trayIcon;
private static PopupMenu createTrayMenu()
ActionListener exitListener = new ActionListener()
public void actionPerformed(ActionEvent e)
System.out.println("Bye from the tray");
System.exit(0);
;
ActionListener executeListener = new ActionListener()
public void actionPerformed(ActionEvent e)
JOptionPane.showMessageDialog
(null, "Popup from the action on the systray!",
"User action", JOptionPane.INFORMATION_MESSAGE);
trayIcon.displayMessage
("Done", "You can do it again if you want!",
TrayIcon.MessageType.INFO);
;
PopupMenu menu = new PopupMenu();
MenuItem execItem = new MenuItem("Action...");
execItem.addActionListener(executeListener);
menu.add(execItem);
MenuItem exitItem = new MenuItem("Exit");
exitItem.addActionListener(exitListener);
menu.add(exitItem);
return menu;
/**
* using a built-in icon
* we need to convert the icon to an Image
*/
private static TrayIcon createTrayIconFromBuiltInIcon()
Icon icon = UIManager.getIcon("OptionPane.warningIcon");
PopupMenu popup = createTrayMenu();
Image image = iconToImage(icon);
TrayIcon ti = new TrayIcon(image, "Java System Tray Demo", popup);
ti.setImageAutoSize(true);
return ti;
static Image iconToImage(Icon icon)
if (icon instanceof ImageIcon)
return ((ImageIcon)icon).getImage();
else
int w = icon.getIconWidth();
int h = icon.getIconHeight();
GraphicsEnvironment ge =
GraphicsEnvironment.getLocalGraphicsEnvironment();
GraphicsDevice gd = ge.getDefaultScreenDevice();
GraphicsConfiguration gc = gd.getDefaultConfiguration();
BufferedImage image = gc.createCompatibleImage(w, h);
Graphics2D g = image.createGraphics();
icon.paintIcon(null, g, 0, 0);
g.dispose();
return image;
public static void main(String[] args) throws Exception
if (!SystemTray.isSupported())
System.out.println
("System tray not supported on this platform");
System.exit(1);
try
SystemTray sysTray = SystemTray.getSystemTray();
trayIcon = createTrayIconFromBuiltInIcon();
sysTray.add(trayIcon);
trayIcon.displayMessage("Ready",
"Tray icon started and tready", TrayIcon.MessageType.INFO);
catch (AWTException e)
System.out.println("Unable to add icon to the system tray");
System.exit(1);
【讨论】：
一个小时前已经评论过，再做一次：您认为这将如何帮助解决异常的原因，即 laf 提供的图标无法处理空组件？ ...这个错误的答案怎么会卷土重来？ @kleopatra，可能是因为它工作正常，如我的测试用例所示。 所以你很幸运使用了 OptionPane.warningIcon ;-) 尝试使用 checkbox.icon (metal-/windowsLAF)，这是要解决的问题... 很高兴知道，@kleopatra。其他一些人也出现了同样的问题（CheckBoxMenuItem），但大多数都可以。我给你+1 ;-) @RealHowTo 您测试了多少 LAF？试试 Windows 经典版。【参考方案3】：试试这个：
icon.paintIcon(new JCheckBox(), image.getGraphics(), 0, 0);
我无法准确解释为什么它需要JCheckBox。也许它因图标而异？ NullPointerException 来自MetalIconFactory 中的这一行，用于"CheckBox.icon"：
ButtonModel model = ((JCheckBox)c).getModel();
【讨论】：
仅供参考：与状态相关的图标绘制在 windowsCheckBoxIcon 中类似。这些图标实现非常糟糕，因为它们假定给定组件是 JCheckBox 类型。按照约定，paintIcon必须处理任意组件类型，包括根本没有以上是关于如何将图标转换为图像的主要内容，如果未能解决你的问题，请参考以下文章