RecentsActivity简介

RecentsActivity 视图界面通过 RecentsPanelView 呈现；

RecentsPanelView 任务栈信息由 RecentTasksLoader 负责加载；

RecentTasksLoader 中由 ActivityManager 的 getRecentTasks 方法获取最近任务栈信息。

RecentTasksLoader 中获取最近任务栈：

final ActivityManager am = (ActivityManager) mContext.getSystemService(Context.ACTIVITY_SERVICE);

final List<ActivityManager.RecentTaskInfo> recentTasks = am.getRecentTasks(MAX_TASKS, ActivityManager.RECENT_IGNORE_UNAVAILABLE);

参数2说明：

    /**
     * Flag for use with {@link #getRecentTasks}: return all tasks, even those
     * that have set their
     * {@link android.content.Intent#FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS} flag.
     */
    public static final int RECENT_WITH_EXCLUDED = 0x0001;
   
    /**
     * Provides a list that does not contain any
     * recent tasks that currently are not available to the user.
     */
    public static final int RECENT_IGNORE_UNAVAILABLE = 0x0002;

getRecentsTasks源码：

  /**
     * Return a list of the tasks that the user has recently launched, with
     * the most recent being first and older ones after in order.
     *
     * @param maxNum The maximum number of entries to return in the list.  The
     * actual number returned may be smaller, depending on how many tasks the
     * user has started and the maximum number the system can remember.
     * @param flags Information about what to return.  May be any combination
     * of {@link #RECENT_WITH_EXCLUDED} and {@link #RECENT_IGNORE_UNAVAILABLE}.
     *
     * @return Returns a list of RecentTaskInfo records describing each of
     * the recent tasks.
     *
     * @throws SecurityException Throws SecurityException if the caller does
     * not hold the {@link android.Manifest.permission#GET_TASKS} permission.
     */
    public List<RecentTaskInfo> getRecentTasks(int maxNum, int flags)
            throws SecurityException {
        try {
            return ActivityManagerNative.getDefault().getRecentTasks(maxNum,
                    flags);
        } catch (RemoteException e) {
            // System dead, we will be dead too soon!
            return null;
        }
    }