had been doing是什么用法

1、had been doing是英语16种时态当中的一种，叫做过去完成进行时。表达的是动作在过去某一时间之前开始并延续到过去的这个时间,这一动作可能还在进行,也可能已经停止.。

2、举个例子：I had been looking for it for days before I found it.这东西我找了好多天才找着的

3、表示反复的动作。例句：You had been giving me everything.