最简单Ext.Tree扩展CheckBox的方法

< language=javascript type=text/javascript>var tree = null;var txtChkValue = document.getElementById("txtChkValue");Ext.onReady(function(){    Ext.BLANK_IMAGE_URL = "../../Js/extjs2/resources/images/default/s.gif"    // shorthand    var Tree = Ext.tree;        tree = new Tree.TreePanel({        el:'tree-div',        autoScroll:true,        animate:true,        enableDD:false,        containerScroll: true,         onlyLeafCheckable: false,//对树所有结点都可选         loader: new Tree.TreeLoader({            dataUrl:'../../getTreeData.aspx'                    }),        margins:'15,15,15,15',        border:false            });        tree.on('checkchange', function(node, checked) {                    node.expand();                    node.attributes.checked = checked;                    var parentNode = node.parentNode;                    if(checked){                        if(parentNode!=null&&parentNode.id!='source'){                            //如果是选中,把父节点保持选中状态                            parentNode.ui.toggleCheck(true);                            parentNode.attributes.checked = true;                        }                    }else{                        //如果所有子节点都没选中，取消根节点选中状态                        if(parentNode!=null&&parentNode.id!='source'){                            var chk = false;                            parentNode.eachChild(function(child) {                                if(child.attributes.checked)chk=true;                            });                            parentNode.ui.toggleCheck(chk);                            parentNode.attributes.checked = chk;                        }                    }                    node.eachChild(function(child) {                        child.ui.toggleCheck(checked);                        child.attributes.checked = checked;                        child.fireEvent('checkchange', child, checked);                    });                    txtChkValue.value = tree.getChecked('id');                }, tree);    // set the root node    var root = new Tree.AsyncTreeNode({        text: '请选择要生成的栏目',        draggable:false,        id:'source'    });    tree.setRootNode(root);    // render the tree    tree.render();    root.expand();});