JTree多節點渲染器問題

Question

在以下JTreeBasics.java文件中，BlackBox和WhiteBox節點是否可以具有不同的圖像？

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.tree.*;
import java.lang.reflect.*;

public class JTreeBasics{
    JFrame f;
    DefaultMutableTreeNode root,n1,n2,ln1,ln2,ln3,ln4,ln3_1,ln3_2,ln3_1_1,ln3_1_2,ln3_1_2_1;
    DefaultTreeModel dtm;
    JTree tree;

    public JTreeBasics() {
        f=new JFrame("JTree Demo");
        f.setSize(400, 500) ;
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        root=new DefaultMutableTreeNode("BlackBox");

            n1=new DefaultMutableTreeNode("WhiteBox");
            root.add(n1);
                ln1=new DefaultMutableTreeNode("Item");
                n1.add(ln1);

            n2=new DefaultMutableTreeNode("BlackBox");
            root.add(n2);
                ln2=new DefaultMutableTreeNode("Item");
                n2.add(ln2);
                ln3=new DefaultMutableTreeNode("WhiteBox");
                n2.add(ln3);
                    ln3_1=new DefaultMutableTreeNode("WhiteBox");

                        ln3_1_1=new DefaultMutableTreeNode("Item");
                        ln3_1.add(ln3_1_1);
                        ln3_1_2=new DefaultMutableTreeNode("BlackBox");

                            ln3_1_2_1=new DefaultMutableTreeNode("Item");
                            ln3_1_2.add(ln3_1_2_1);

                        ln3_1.add(ln3_1_2);

                    ln3.add(ln3_1);
                    ln3_2=new DefaultMutableTreeNode("Item");
                    ln3.add(ln3_2);
                ln4=new DefaultMutableTreeNode("Item");
                n2.add(ln4);

        dtm=new DefaultTreeModel(root);
        tree=new JTree(dtm);

        //most imp. line of this code
        installingCustomRenderer() ;

        f.add(tree);
        f.setVisible(true);
    }

    private void installingCustomRenderer(){
        CustomTreeCellRenderer renderer = new CustomTreeCellRenderer();


        tree.setCellRenderer(renderer);
    }

    public static void main(String[] args){
        new JTreeBasics();
    }
}

class CustomTreeCellRenderer extends DefaultTreeCellRenderer{

    private Font plainFont = null;
    private Font italicFont = null;

    public Component getTreeCellRendererComponent(JTree tree,
        Object value, boolean selected, boolean expanded,
        boolean leaf, int row, boolean hasFocus){

        super.getTreeCellRendererComponent(tree, value,
        selected, expanded, leaf, row, hasFocus);

        plainFont = getFont();

        italicFont = plainFont.deriveFont(Font.ITALIC) ;

        setFont(italicFont);

        return this;
    }
}

Answer 1

是的，在getTreeCellRendererComponent您需要查詢value並使用適當的圖像調用setIcon() 。

注意：默認實現會查看expanded和leaf的值，以在打開，關閉或葉子圖標之間進行選擇。

Answer 2

在渲染器代碼中，將超級調用的返回值轉換為JLabel（因為DefaultTreeCellRenderer 是 JLabel），然后可以根據“值”在其上設置setIcon（）。