在网上找了好久的上传头像并预览的例子，有是有，但就是不好改，或者是效果不是很好看，所以就决定自己写一个，个人觉得还不错，挺好的，需要的朋友可以下载下来看看！-The Internet looking for a long time to upload avatar and preview example, there is, but is not good, or the effect is not very good, so I decided to write one, personal f