如何让一个activity只要不在显示的时候就finish掉呢？ FLAG_ACTIVITY_NO_HISTORY

FLAG_ACTIVITY_NO_HISTORY  ：If set, the new activity is not kept in the history stack. As soon as the user navigates away from it, the activity is finished. This may also be set with the noHistoryattribute.

A 启动B 的时候 设置    intent.setFlags(Intent.FLAG_ACTIVITY_NO_HISTORY);  然后 B 启动 C  ，

然后  按返回键，这个时候界面显示不是B，而是 A 。注意B  是在这个时候执行的    finish  。