https://stackoverflow.com/questions/27829625/android-use-a-different-icon-for-recent-apps
试下这个里面的解决方案。在BaseActivity的onCreate 加入如下代码。
Bitmap recentsIcon; // Initialize this to whatever you want
String title; // You can either set the title to whatever you want or just use null and it will default to your app/activity name
int color; // Set the color you want to set the title to, it's a good idea to use the colorPrimary attribute
ActivityManager.TaskDescription description = new ActivityManager.TaskDescription(title, recentsIcon, color);
this.setTaskDescription(description);