在class上绑定的事件,点击图片的时候无法触发
<div id="files" class="files">
<div>
<p>
<canvas width="80" height="80"></canvas>
<br><span class="preview"></span><span class="name"></span><span class="size"></span><br>
<button class="btn btn-primary">Upload</button>
</p>
</div>
</div>