Bootstrap Collapse的使用

1、效果图：

2、当点击B或C时，A自动收缩：

3、html代码：

<div class="panel-group" id="accordion" role="tablist" aria-multiselectable="true">
												<div class="panel panel-default">
													<div class="panel-heading" role="tab" id="headingOne">
														<h4 class="panel-title">
															<a class="collapsed" role="button" data-toggle="collapse" data-parent="#accordion" href="#collapseOne" aria-expanded="true" aria-controls="collapseOne">
																A
															a>
														h4>
													div>
													<div id="collapseOne" class="panel-collapse  collapse in" role="tabpanel" aria-labelledby="headingOne">
														<ul class="list-group">
															<li class="list-group-item">1li>
															<li class="list-group-item">2li>
															<li class="list-group-item">3li>
														ul>
													div>
												div>

												<div class="panel panel-default">
													<div class="panel-heading" role="tab" id="headingTwo">
														<h4 class="panel-title">
															<a class="collapsed" role="button" data-toggle="collapse" data-parent="#accordion" href="#collapseTwo" aria-expanded="false" aria-controls="collapseTwo">
																B
															a>
														h4>
													div>
													<div id="collapseTwo" class="panel-collapse collapse" role="tabpanel" aria-labelledby="headingTwo">
														<ul class="list-group">
															<li class="list-group-item">1li>
															<li class="list-group-item">2li>
															<li class="list-group-item">3li>
														ul>
													div>
												div>

												<div class="panel panel-default">
													<div class="panel-heading" role="tab" id="headingThree">
														<h4 class="panel-title">
															<a class="collapsed" role="button" data-toggle="collapse" data-parent="#accordion" href="#collapseThree" aria-expanded="false" aria-controls="collapseThree">
																C
															a>
														h4>
													div>
													<div id="collapseThree" class="panel-collapse collapse" role="tabpanel" aria-labelledby="headingThree">
														<ul class="list-group">
															<li class="list-group-item">1li>
															<li class="list-group-item">2li>
															<li class="list-group-item">3li>
														ul>
													div>
												div>
											div>

其中最关键的是：data-parent=“#accordion”、aria-expanded=“true”、class=“panel-collapse collapse in”
（1）data-parent=“#accordion”：它指定的当前折叠框是在哪个下边，就是类似于分组，是指的在哪个分组下，该分组指定了ID（

（2）aria-expanded="true"表示默认展开，此属性需要配合class="panel-collapse collapse in"使用，否则会无法无法展开。
另需要注意：aria-controls、aria-labelledby的值。