1.源码路径:
frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/NotificationListener.java​

2.NotificationListener类是负责处理监听通知更新并将其传递给向用户显示的NotificationPresenter,也就是SystemUI中监听到系统通知的起点.

public class NotificationListener extends NotificationListenerWithPlugins {private static final String TAG = "NotificationListener";private static final boolean DEBUG = StatusBar.DEBUG;private final Context mContext;private final NotificationManager mNotificationManager;private final Handler mMainHandler;private final List<NotificationHandler> mNotificationHandlers = new ArrayList<>();private final ArrayList<NotificationSettingsListener> mSettingsListeners = new ArrayList<>();public NotificationListener(Context context,NotificationManager notificationManager,@Main Handler mainHandler) {mContext = context;mNotificationManager = notificationManager;mMainHandler = mainHandler;}public void addNotificationHandler(NotificationHandler handler) {if (mNotificationHandlers.contains(handler)) {throw new IllegalArgumentException("Listener is already added");}mNotificationHandlers.add(handler);}public void addNotificationSettingsListener(NotificationSettingsListener listener) {mSettingsListeners.add(listener);}@Overridepublic void onListenerConnected() {if (DEBUG) Log.d(TAG, "onListenerConnected");onPluginConnected();final StatusBarNotification[] notifications = getActiveNotifications();if (notifications == null) {Log.w(TAG, "onListenerConnected unable to get active notifications.");return;}final RankingMap currentRanking = getCurrentRanking();mMainHandler.post(() -> {final List<Ranking> newRankings = new ArrayList<>();for (StatusBarNotification sbn : notifications) {newRankings.add(getRankingOrTemporaryStandIn(currentRanking, sbn.getKey()));}final RankingMap completeMap = new RankingMap(newRankings.toArray(new Ranking[0]));for (StatusBarNotification sbn : notifications) {for (NotificationHandler listener : mNotificationHandlers) {listener.onNotificationPosted(sbn, completeMap);}}for (NotificationHandler listener : mNotificationHandlers) {listener.onNotificationsInitialized();}});onSilentStatusBarIconsVisibilityChanged(mNotificationManager.shouldHideSilentStatusBarIcons());}@Overridepublic void onNotificationPosted(final StatusBarNotification sbn,final RankingMap rankingMap) {if (DEBUG) Log.d(TAG, "onNotificationPosted: " + sbn);/*
1.当收到通知时,会调用该方法,然后把通知Handler更新界面,所以可以在这个屏蔽通知的显示,可以通过参数设置,或者通过设置系统参数,这样可以通过配置参数就可以自由控制通知的显示,如下面,设置android_statusbar_visible参数,默认值为false,即不显示通知,if(!SystemProperties.getBoolean("android_statusbar_visible",false)) return;*/if (sbn != null && !onPluginNotificationPosted(sbn, rankingMap)) {mMainHandler.post(() -> {processForRemoteInput(sbn.getNotification(), mContext);for (NotificationHandler handler : mNotificationHandlers) {handler.onNotificationPosted(sbn, rankingMap);}});}}@Overridepublic void onNotificationRemoved(StatusBarNotification sbn, RankingMap rankingMap,int reason) {if (DEBUG) Log.d(TAG, "onNotificationRemoved: " + sbn + " reason: " + reason);/*
2.  当通知被移除时,也需要坐下过滤if(!SystemProperties.getBoolean("android_statusbar_visible",false)) return;*/if (sbn != null && !onPluginNotificationRemoved(sbn, rankingMap)) {mMainHandler.post(() -> {for (NotificationHandler handler : mNotificationHandlers) {handler.onNotificationRemoved(sbn, rankingMap, reason);}});}}@Overridepublic void onNotificationRemoved(StatusBarNotification sbn, RankingMap rankingMap) {onNotificationRemoved(sbn, rankingMap, UNDEFINED_DISMISS_REASON);}@Overridepublic void onNotificationRankingUpdate(final RankingMap rankingMap) {if (DEBUG) Log.d(TAG, "onRankingUpdate");/*
3.这里是更新通知在通知列表上的排列,通知也需要坐下过滤if(!SystemProperties.getBoolean("android_statusbar_visible",false)) return;*/if (rankingMap != null) {RankingMap r = onPluginRankingUpdate(rankingMap);mMainHandler.post(() -> {for (NotificationHandler handler : mNotificationHandlers) {handler.onNotificationRankingUpdate(r);}});}}......
}