创建JToolBar时出错

Question

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在将按钮添加到工具栏时，我会得到此错误。

Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: Sketcher.SketcherFrame$ColorAction cannot be cast to javax.swing.Icon

ColorAction是一个类，用于创建更改JFrame背景色的工具栏按钮。它扩展了javax.swing.AbstractAction。

ColorAction类型的按钮存储在ColorActions[]数组中，并将其SMALL_ICON属性设置为适当的值。

堆栈跟踪：

Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: Sketcher.SketcherFrame$ColorAction cannot be cast to javax.swing.Icon
    at javax.swing.AbstractButton.setIconFromAction(Unknown Source)
    at javax.swing.AbstractButton.configurePropertiesFromAction(Unknown Source)
    at javax.swing.AbstractButton.setAction(Unknown Source)
    at javax.swing.JButton.<init>(Unknown Source)
    at Sketcher.SketcherFrame.addToolBarButton(SketcherFrame.java:182)
    at Sketcher.SketcherFrame.createToolbar(SketcherFrame.java:174)
    at Sketcher.SketcherFrame.<init>(SketcherFrame.java:27)
    at Sketcher.Sketcher.createGUI(Sketcher.java:16)
    at Sketcher.Sketcher.access$1(Sketcher.java:15)
    at Sketcher.Sketcher$1.run(Sketcher.java:10)
    at java.awt.event.InvocationEvent.dispatch(Unknown Source)
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access$000(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)

高亮显示的方法

private void createColorMenu() {
    createElementColorActions();
    colorMenu = new JMenu("Color");
    colorMenu.setMnemonic('M');
    createRadioButtonDropDown(colorMenu,colorActions,blueAction);
    menuBar.add(colorMenu);
}  

和

private void createRadioButtonDropDown(JMenu menu, Action[] actions,Action selected){
        ButtonGroup group = new ButtonGroup();
        JRadioButtonMenuItem item = null;
        for(Action action : actions){
            group.add(menu.add(item = new JRadioButtonMenuItem(action)));
            if(action==selected){
                item.setSelected(true);
            }
        }
    }

和

private void addToolBarButton(Action action){
        >>JButton button = new JButton(action);
        button.setBorder(BorderFactory.createCompoundBorder(new EmptyBorder(2,5,5,2),
                            BorderFactory.createRaisedBevelBorder()));
        button.setHideActionText(true);
        toolBar.add(button);
    }

和

private void createToolbar(){
        for(FileAction action : fileActions){
            if(action!=exitAction && action!=closeAction){
                addToolBarButton(action);
            }
        }
        toolBar.addSeparator();
        for(ColorAction action : colorActions){
            >>addToolBarButton(action);
        }
        toolBar.addSeparator();
        for(TypeAction action : typeActions){
            addToolBarButton(action);
        }
    }

包含图像路径的常量文件

import java.awt.Color;
import javax.swing.*;
public class SketcherConstants {
    public final static int LINE = 101;
    public final static int RECTANGLE = 102;
    public final static int CIRCLE = 103;
    public final static int CURVE = 104;

    public final static int DEFAULT_ELEMENT_TYPE = LINE;
    public final static Color DEFAULT_ELEMENT_COLOR = Color.blue;

    public final static String imagePath = "H:/Fasih/SketcherIcons/";
    public static final Icon NEW16 = new ImageIcon(imagePath+"new.GIF");
    public static final Icon OPEN16 = new ImageIcon(imagePath+"open.GIF");
    public static final Icon SAVE16 = new ImageIcon(imagePath+"save.GIF");
    public static final Icon PRINT16 = new ImageIcon(imagePath+"print.GIF");
    public static final Icon SAVEAS16 = new ImageIcon(imagePath+"saveas.GIF");

    public static final Icon LINE16 = new ImageIcon(imagePath+"line.PNG");
    public static final Icon CURVE16 = new ImageIcon(imagePath+"curve.PNG");
    public static final Icon RECTANGLE16 = new ImageIcon(imagePath+"square.PNG");
    public static final Icon CIRCLE16 = new ImageIcon(imagePath+"circle.PNG");

    public static final Icon RED16= new ImageIcon(imagePath+"red.GIF");
    public static final Icon GREEN16= new ImageIcon(imagePath+"green.GIF");
    public static final Icon YELLOW16= new ImageIcon(imagePath+"yellow.GIF");
    public static final Icon BLUE16= new ImageIcon(imagePath+"blue.GIF");
}

和

class ColorAction extends AbstractAction {
        public ColorAction(String name,Color color){
            super(name);
            this.color = color;
        }
        public ColorAction(String name,Color color,char ch,int modifiers){
            this(name,color);
            putValue(ACCELERATOR_KEY,KeyStroke.getKeyStroke(ch,modifiers));
            int index = name.toUpperCase().indexOf(ch);
            if(index!=-1){
                putValue(DISPLAYED_MNEMONIC_INDEX_KEY,index);
            }
        }
        public void actionPerformed(ActionEvent e){
            elementColor = color;
            getContentPane().setBackground(color);
        }
        private Color color;
    }

如果我删除的颜色按钮，然后打开，关闭，保存按钮是添加很好。我不知道为什么这些不能加进去。

Answer 1

首先，请指出触发此异常的代码中的确切行。查看堆栈跟踪，我假设这是SketcherFrame.java第153行。这样更容易调试。

但是，即使没有这一点，您的问题似乎是您混淆了AbstractAction和Icon。不管抛出什么，异常都是期望Icon的实现，而您给了它一个AbstractAction的实现。

我可以提出两件事：

1. 还可以在Icon中实现SketcherFrame$ColorAction。无论如何，您可以实现多个接口。但是..。
2. ...in我的观点是，创建一个AbstractAction和Icon的类是一个错误的设计决策。由于您似乎在使用内部类，所以只需创建一个实现Icon的内部类，并将其传递给触发该异常的任何内容。