FLAG_ACTIVITY_TASK_ON_HOME :把当前新启动的任务置于Home任务之上，也就是按back键从这个任务返回的时候会回到home，即使这个不是他们最后看见的activity
注意这个标记必须和FLAG_ACTIVITY_NEW_TASK一起使用。
实例：
一个apk中有MainActivity,ActivityA，点击MainActivity启动ActivityA,
public void onClick(View arg0) {
// TODO Auto-generated method stub
Log.i(TAG, "--onClick--task id = " + getCurrentTaskId());
Intent intent = new Intent("com.leaves.ipanel.ActivityA");
intent.addFlags(Intent.FLAG_ACTIVITY_TASK_ON_HOME | Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);
} ACTIVITY MANAGER ACTIVITIES (dumpsys activity activities)
Main stack:
TaskRecord{43bb4e48 #7 A com.leaves.ipanel.ActivityA U 0} Intent { act=com.leaves.ipanel.ActivityA flg=0x10004000 cmp=com.leaves.ipanel/.ActivityA }
Hist #2: ActivityRecord{4274a5c0 u0 com.leaves.ipanel/.ActivityA}
Intent { act=com.leaves.ipanel.ActivityA flg=0x10004000 cmp=com.leaves.ipanel/.ActivityA }
ProcessRecord{4267a850 1924:com.leaves.ipanel/u0a10061}
TaskRecord{426f4820 #2 A com.android.launcher U 0}
Intent { act=android.intent.action.MAIN cat=[android.intent.category.HOME] flg=0x10600000 cmp=com.android.launcher/com.android.launcher2.Launcher }
Hist #1: ActivityRecord{4291c7b0 u0 com.android.launcher/com.android.launcher2.Launcher}
Intent { act=android.intent.action.MAIN cat=[android.intent.category.HOME] flg=0x10000000 cmp=com.android.launcher/com.android.launcher2.Launcher }
ProcessRecord{4267f0b8 636:com.android.launcher/1000}
TaskRecord{4360ab48 #5 A com.leaves.ipanel U 0}
Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.leaves.ipanel/.MainActivity bnds=[163,708][307,852] }
Hist #0: ActivityRecord{426b6380 u0 com.leaves.ipanel/.MainActivity}
Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.leaves.ipanel/.MainActivity bnds=[163,708][307,852] }
ProcessRecord{4267a850 1924:com.leaves.ipanel/u0a10061} 堆栈信息中我们可以看出，ActivityA位于了Launcher即Home之上，而MainActivity被移动到了后台，所以这个时候我们按返回键，将返回到Home，而不是MainActivity
