You can do this by adding two buttons: one that expands and one that collapses all the top-level tree items.
为此，您可以添加两个按钮：一个用于展开所有顶级树项目，一个用于折叠树项目。
A useful feature to add to your applications is the capability to expand or collapse all top-level tree items.
可以向应用程序中添加一个有用的特性，那就是展开或折叠所有顶级树项目的功能。
Ten thousand years of tree rings show that the carbon-14 level rises and falls about every 420 years.
一万年的树木年轮显示，碳14水平大约每420年上升和下降一次。
One particular sequence in the first level has players scurry through backyards and finally climb into a tree house.
第一关的某特定情节要求玩家匆匆穿过后院，最后爬进一间树屋。
The tree top is level with the roof.
树梢和屋顶齐平。
Possible nodes on the tree would be age, income level, current number of cars, mariatl status, kids, homeowner, or renter.
这个树上的节点可以是年龄、收入水平、目前拥有的车的数量、婚姻状况、有无孩子、房主还是租户。
If so, then the current entry must be a folder, and you push its name and recursion level onto an auxiliary stack as well as adding it to the tree.
如果具有子代，那么当前条目必须是一个文件夹，您要将其名称和递归级别推到辅助堆栈上并将它们添加到树中。
This is why certain policies described later in the article, such as layout, component, and theme policies, can be defined at any level of the hierarchy of the device tree.
这就是某些策略在文章的后面才介绍的原因，像布局、组件、主题策略，这些都能被定义在设备树状图中的任何层次。
Perched above the forest floor, these tree houses are connected by zip lines and sky Bridges, accessible by stairs and ladders from the ground level.
坐落在森林的地面之上的这些树上小屋用铁链和空中桥梁连接着，还有通到地面上的梯子。
At rural or local level slaughtering is often either carried out under a tree or in deteriorated and outdated slaughter units without any waste treatment facilities.
在农村和当地，屠宰通常是在树下或老旧的屠宰房内进行，没有任何垃圾处理设施。
In DOM Level 2, renaming a node was a relatively expensive operation: You had to create a new node, copy all the data to the new node, insert the new node into the tree, and delete the old one.
在DOMLevel2中，重命名一个节点的操作代价较高：必须在树中创建一个新节点，并删除老的节点。
Each level of the Dojo tree consists of an icon and a label.
dojo树的每一层都包含一个图标和一个标签。
Limit the work-flow tree to the level of planners or contributors while not showing planning objects in the tree.
将工作流树限制到规划者（planner）或贡献者（contributor）级别，同时不在树中显示规划对象。
The sample application's custom JSF component created only 100 tree nodes (at the root level) and showed the option 'show more...' in the end.
本文例子应用的自定义JSF组件只创建100个树节点(在根一级上)并在最后显示‘Showmore…’选项。
However, if you have two elements where there is no direct parent-child relationship and they do not lie on the same level in the tree structure, their event firing sequence is not fixed.
但是，如果您拥有两个没有上下级关系的元素，而且它们在树形结构中不是同一层次，那么它们的事件引发序列就是不同的。
Discovering the entire inheritance tree structure from an existing system is particularly useful, because it helps you uncover what the top-level class is and what subclasses are in the tree.
从一个已存在系统中发现整个的继承树结构是相当有用的，因为它能向您揭露在树中什么是顶级类以及什么是子类。
In event tree studies, now an event tree is obviously a high level look at what things you need to function, to be able to successfully manage this particular accident.
在事件树的研究中，一个事件树明显是，高度注意你们需要运行什么事情，从而能够成功地，处理好这个特别的事故。
Mixed flocks of several species often travel together, but when they are feeding or resting you will spot different birds on the ground, at mid-level heights and at the tree tops.
很多种鸟常常混群共同迁徙，但是当他们停下来觅食休息的时候，你就会发现不同的种类有的在地面上，有的在中层高度，有的则在树顶处。
The complete set of class loaders make up a tree-structured hierarchy with different types of classes loaded at each level.
整个类装入器集合形成了树状结构的层次结构，在其每个层次上都可装入不同类型的类。
If the above checks result in a valid schema being found embedded in the WSDL at the correct level, the schema is copied to the output logical tree.
如果上面的检查得到了在WSDL中的正确级别嵌入的有效模式，会将该模式复制到数据逻辑树中。
The judges felt this represented a step change on the existing strategy tree, and laddered the concept to a whole new level.
评委们觉得这个词表达了现存“战略树”迈出了改进的一步，而且使(战略)概念跨向了一个全新的水准。
For each top-level feature, or facet, there is a sub-tree of possible values.
对于每个顶级特性或方面，都有一个可能值组成的子树。
Never let the water level fall below the base of the tree or the cut end may seal over, preventing further water intake.
不要让水位降到树基以下，或者树干截面以下，否则截面干涸以后，松树就无法充足的吸收水分了。
If scientists know what temperature and moisture level make the tree happy, they can use the thickness to gauge what the climate was like that year.
如果科学家弄清楚什么样的温度和湿度最适合树木生长，他们就可以推算出那一年的气候情况。
The algorithm is simple; it iterates through the top-level items of the tree and compares their text contents with the search string (lines 43 to 52 in listing 6).
算法很简单，它对树的顶级项目进行迭代，并将其文本内容与搜索字符串进行比较(清单6中的第43- 52行)。
If you find yourself needing to do this, consider whether a tree control or other element better suited to multiple-level hierarchies would be more appropriate.
如果你发现需要这样做，树状菜单或者其他的适合显示多级结构的元素可能更合适。
Indeed, DB2 can split a collection (or sub-tree) of nodes at any level of the document hierarchy as needed.
实际上，DB 2可以根据需要对文档层次结构中任何级别上的节点集合(即子树)进行拆分。
Well, notice again, on each level of the tree, when I actually do the merging, so this remember, is when I wrote down just the Numbers when I bottomed out with the list of size 1.
请注意，在这棵树中的每一层，我真正做合并时，就将每个大小为1的列表中的，数字写下来。
Further, it is interesting to note that the order in which DB2 has returned the results exposes how the recursion is processed one level at a time, instead of using a tree-walk.
而且，令人感兴趣的是，DB2返回结果时所依照的顺序暴露了递归如何逐层地而不是采用遍历树的方法进行处理。
"Hierarchy" implies a tree structure, where each process belongs to a higher level process (except for processes at the highest level).
“层次结构”意味着是树形结构，每个流程属于较高级别的流程(最高级别的流程除外)。
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