类概述

Helper class for managing multiple running embedded activities in the same process. This class is not normally used directly, but rather created for you as part of theActivityGroup implementation.

首先说明一下，意思就是说这个类不能单独使用，只能在ActivityGroup里面使用。他的作用是管理多个正在运行的嵌入的activity的界面。。。

关于成员方法的说明：

其实看SDK也就可以知道了。。。

主要的就是派遣方法，让某一个操作可以作用于在这个ActivityGroup里面的Activity

Window	destroyActivity(String id, boolean finish) 摧毁该ID的activity。。。。并且返回你删除的activity的view。。。Destroy the activity associated with a particular id.
void	dispatchCreate(Bundle state) Restore a state that was previously returned by saveInstanceState().
void	dispatchDestroy(boolean finishing) Called by the container activity in its onDestroy() so that LocalActivityManager can perform the corresponding action on the activities it holds.
void	dispatchPause(boolean finishing) Called by the container activity in its onPause() so that LocalActivityManager can perform the corresponding action on the activities it holds.
void	dispatchResume() Called by the container activity in its onResume() so that LocalActivityManager can perform the corresponding action on the activities it holds.
void	dispatchStop() Called by the container activity in its onStop() so that LocalActivityManager can perform the corresponding action on the activities it holds.
Activity	getActivity(String id) Return the Activity object associated with a string ID.
Activity	getCurrentActivity() Retrieve the Activity that is currently running.
String	getCurrentId() Retrieve the ID of the activity that is currently running.
void	removeAllActivities() Remove all activities from this LocalActivityManager, performing an onDestroy() on any that are currently instantiated.
Bundle	saveInstanceState() Retrieve the state of all activities known by the group.
Window	startActivity(String id, Intent intent) Start a new activity running in the group.

下面主要说明一下startActivity(String id, Intent intent)这个方法：

Start a new activity running in the group. Every activity you start must have a unique string ID associated with it -- this is used to keep track of the activity, so that if you later call startActivity() again on it the same activity object will be retained.

When there had previously been an activity started under this id, it may either be destroyed and a new one started, or the current one re-used, based on these conditions, in order:

• If the Intent maps to a different activity component than is currently running, the current activity is finished and a new one started.
• If the current activity uses a non-multiple launch mode (such as singleTop), or the Intent has the FLAG_ACTIVITY_SINGLE_TOP flag set, then the current activity will remain running and its Activity.onNewIntent() method called.
• If the new Intent is the same (excluding extras) as the previous one, and the new Intent does not have the FLAG_ACTIVITY_CLEAR_TOP set, then the current activity will remain running as-is.
• Otherwise, the current activity will be finished and a new one started.

If the given Intent can not be resolved to an available Activity, this method throws ActivityNotFoundException.

Warning: There is an issue where, if the Intent does not include an explicit component, we can restore the state for a different activity class than was previously running when the state was saved (if the set of available activities changes between those points).

参数

id	Unique identifier of the activity to be started
intent	The Intent describing the activity to be started

返回值

• Returns the window of the activity. The caller needs to take care of adding this window to a view hierarchy, and likewise dealing with removing the old window if the activity has changed.

简单的翻译一下就是：

新建并且运行一个activity在activitygroup里面，主要的说明就在这个String id里面，说尽量在新建时候不要是用同一个

id，因为这个样子就会到导致如果你使用再一次 startActivity() ，那么就会继续保留下去。。。

当这个activity需要被销毁的时候：

如果有以下的情况就可以不用销毁。其他都需要销毁。。。

1.已经有一个老的intent，而且新的intent没有使用FLAG_ACTIVITY_CLEAR_TOP 这个参数

2.当前的activity使用的是uses a non-multiple launch mode 的话

3.intent还有不从的界面组件。。。