break;
}
// 从上向下取消的时候
if(index == children.size())
{
for(int i = 0; i < children.size(); ++ i)
{
CheckBoxTreeNode node = (CheckBoxTreeNode)children.get(i);
if(node.isSelected() != _isSelected)
node.setSelected(_isSelected);
}
}
}
// 向上取消，只要存在一个子节点不是选上的，那么父节点就不应该被选上。
CheckBoxTreeNode pNode = (CheckBoxTreeNode)parent;
if(pNode != null && pNode.isSelected() != _isSelected)
pNode.setSelected(_isSelected);
}
}
}
第一个差异通过继承DefaultMutableTreeNode定义CheckBoxTreeNode解决了，接下来需要解决第二个差异。第二个差异是外观上的差异，JTree的每个结点是通过TreeCellRenderer进行显示的。为了解决第二个差异，我们定义一个新的类CheckBoxTreeCellRenderer，该类实现了TreeCellRenderer接口。CheckBoxTreeRenderer的源代码如下：
package demo;
import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import javax.swing.JCheckBox;
import javax.swing.JPanel;
import javax.swing.JTree;
import javax.swing.UIManager;
import javax.swing.plaf.ColorUIResource;
import javax.swing.tree.TreeCellRenderer;
public class CheckBoxTreeCellRenderer extends JPanel implements TreeCellRenderer
{
protected JCheckBox check;
protected CheckBoxTreeLabel label;
public CheckBoxTreeCellRenderer()
{
setLayout(null);
add(check = new JCheckBox());
add(label = new CheckBoxTreeLabel());
check.setBackground(UIManager.getColor("Tree.textBackground"));
label.setForeground(UIManager.getColor("Tree.textForeground"));
/**
* 返回的是一个
JPanel对象，该对象中包含一个JCheckBox对象* 和一个
JLabel对象。并且根据每个结点是否被选中来决定JCheckBox* 是否被选中。
*/
@Override
public Component getTreeCellRendererComponent(JTree tree, Object value,
boolean selected, boolean expanded, boolean leaf, int row,
boolean hasFocus)
{
String stringValue = tree.convertValueToText(value, selected, expanded, leaf, row, hasFocus);
setEnabled(tree.isEnabled());
check.setSelected(((CheckBoxTreeNode)value).isSelected());
label.setFont(tree.getFont());
label.setText(stringValue);
label.setSelected(selected);
label.setFocus(hasFocus);
if(leaf)
label.setIcon(UIManager.getIcon("Tree.leafIcon"));
else if(expanded)
label.setIcon(UIManager.getIcon("Tree.openIcon"));
else
label.setIcon(UIManager.getIcon("Tree.closedIcon"));
return this;
}
@Override
public Dimension getPreferredSize()
{
Dimension dCheck = check.getPreferredSize();
Dimension dLabel = label.getPreferredSize();
return new Dimension(dCheck.width + dLabel.width, dCheck.height < dLabel.height dLabel.height: dCheck.height);
}
@Override
public void doLayout()
{
Dimension dCheck = check.getPreferredSize();
Dimension dLabel = label.getPreferredSize();
int yCheck = 0;
int yLabel = 0;
if(dCheck.height < dLabel.height)
yCheck = (dLabel.height - dCheck.height) / 2;