文件复制是一个阻塞过程，它意味着你不会得到关于它的状态的任何指示，直到它完成，所以你的进度条将从0跳到100 ...如果仔细观察Windows文件进度条是实际上是一个'marquee'风格吧......

File copy is a blocking process, it means you will not get any indication about it's state until it finished, so your progress bar will jump from 0 to 100...If you look closely Windows file progress bar is in fact a 'marquee' style bar...