Question

我正在使用CustomCellRenderer来显示JTree的节点以显示具有节点的图像如下所示： -

class CustomTreeCellRenderer extends DefaultTreeCellRenderer{

    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);

        JLabel label = (JLabel) this ;

        label.setIcon( new ImageIcon("white.png") ) ;

        return this;
    }
}

我的要求是在某些外部操作上更改节点的图像。我正在尝试重新加载JTree的模型，但它的工作方式如下所示： -

public void actionPerformed(ActionEvent ae) {

        DefaultTreeModel model = (DefaultTreeModel) tree.getModel() ;

        JLabel label = (JLabel) tree.getCellRenderer() ;
        System.out.println(label.getIcon()); //displaying white.png

        label.setIcon( new ImageIcon("black.gif") ) ;


        model.reload() ;
    }

我做错了什么??????

Answer 1

将您的Icon作为字段添加到渲染器类。

更改此字段的值并重新绘制JTree。

class CustomTreeCellRenderer extends DefaultTreeCellRenderer{


    ImageIcon rendererIcon;


    public void setRendererIcon(ImageIcon myIcon){
         this.rendererIcon = myIcon;
    };


    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);

        JLabel label = (JLabel) this ;

        label.setIcon( rendererIcon ) ;

        return this;
    }
}

修改：解释

在您的情况下，更改模型毫无用处。用于显示每个节点的图标是渲染器的一部分。

JTree的渲染器对象不必强制为JComponent。当代码调用JComponent时，它必须是一个提供getTreeCellRendererComponent的对象。

在你的情况下，将getCellRenderer（）转换为JLabel只是运气，因为DefaultTreeCellRenderer的默认实现是JLabel的扩展。

事实上，由于渲染器本身调用了setIcon，因此getIcon方法为您提供放入渲染器的最后一个图标是正常的。

完整代码工作：

import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTree;
import javax.swing.SwingUtilities;
import javax.swing.tree.DefaultTreeCellRenderer;

public class TestJTree {

    private static ImageIcon iconWhite = new ImageIcon("white.jpg");

    private static ImageIcon iconBlack = new ImageIcon("black.jpg");;

    public static void main(String[] args) {
        TestJTree me = new TestJTree();
        me.process();
    }

    private void process() {
        SwingUtilities.invokeLater(new Runnable() {

            public void run() {
                initGui();

            }

        });

    }

    protected void initGui() {
        JFrame frame = new JFrame("Test JTree");
        frame.setContentPane(new JPanel(new BorderLayout()));

        final JTree tree = new JTree();
        frame.getContentPane().add(tree);

        final CustomTreeCellRenderer renderer = new CustomTreeCellRenderer();
        renderer.setRendererIcon(iconWhite);
        tree.setCellRenderer(renderer);

        JPanel panelButtons = new JPanel();

        JButton buttonWhite = new JButton("");
        buttonWhite.setIcon(iconWhite);
        JButton buttonBlack = new JButton("");
        buttonBlack.setIcon(iconBlack);

        buttonBlack.addActionListener(new ActionListener(){

            public void actionPerformed(ActionEvent e) {
                renderer.setRendererIcon(iconBlack);
                tree.repaint();
            }

        });

        panelButtons.add(buttonBlack);
        panelButtons.add(buttonWhite);
        frame.getContentPane().add(panelButtons,BorderLayout.SOUTH);

        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(500,500);
        frame.setVisible(true);


    }

    @SuppressWarnings("serial")
    private static class CustomTreeCellRenderer extends DefaultTreeCellRenderer{


        ImageIcon rendererIcon;


        public void setRendererIcon(ImageIcon myIcon){
             this.rendererIcon = myIcon;
        };


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

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

            JLabel label = (JLabel) ret ;

            label.setIcon( rendererIcon ) ;

            return ret;
        }
    }
}

Answer 2

几点：

使用actionPerformed等方法从表中抓取渲染器并修改它并不常见。您应该注意渲染器是共享的，因此您将影响使用该渲染器的列中的所有单元格
即使您在Icon期间在渲染器实例上设置了actionPerformed，也始终会通过getTreeCellRendererComponent方法访问渲染器以进行绘画，并且您始终将图标设置为“white.png”，所以你永远不会得到“black.gif”来显示。

您拥有的选项是在actionPerformed方法中在模型上设置状态，然后在getTreeCellRendererComponent内，您可以在模型中查询要显示的图标。

例如：

public void actionPerformed(ActionEvent ae) {

    MyCustomTreeModel model = (MyCustomTreeModel) tree.getModel() ;
    ...
    model.setMyState(state); //set the state based on the action
}

：

public Component getTreeCellRendererComponent(JTree tree,
    Object value, boolean selected, boolean expanded,
    boolean leaf, int row, boolean hasFocus)
{
     MyCustomTreeModel model = (MyCustomTreeModel) tree.getModel();
     ....
     setIcon(model.getMyIconBasedOnTheStateISetInActionPerformed());
     return this;    
}

动态更改JTree的节点映像

2 个答案: