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
函数在 image.getGraphics()
上抛出 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!
最佳答案
刚刚找到一个代码片段,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());
}
}
要在您的代码段中使用,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);
关于java - 如何将图标转换为图像,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/5830533/