引言

今天我们主要讲的是SystemUI状态栏里面另一个常见的icons——notification icons，该icons主要用于显示app或者framework发送的各种notification icon，表示当前有新的通知来了，需要下拉通知栏进行查看，以达到提示用户的目的。

正文

本文主要从两个方面讲述下notification icon功能，主要分为初始化流程和通知icon显示流程
话不多说，我们开始吧。

初始化流程

首先我们看下状态栏的布局文件 status_bar.xml

<!-- The alpha of this area is controlled from both PhoneStatusBarTransitions andPhoneStatusBar (DISABLE_NOTIFICATION_ICONS). --><com.android.systemui.statusbar.AlphaOptimizedFrameLayoutandroid:id="@+id/notification_icon_area"android:layout_width="0dip"android:layout_height="match_parent"android:layout_weight="1"android:orientation="horizontal" /><com.android.keyguard.AlphaOptimizedLinearLayout android:id="@+id/system_icon_area"android:layout_width="wrap_content"android:layout_height="match_parent"android:orientation="horizontal">

我们今天讲的notification icons就是这个 android:id="@+id/notification_icon_area" 了。
同样它最外层是一个AlphaOptimizedFrameLayout控件,前文已经说过类似的了,
SystemUI之状态栏status icon加载流程
该控件实现了hasOverlappingRendering()方法,该方法用来标记当前view是否存在过度绘制。

接下来我们看下SystemUI是怎么加载这个AlphaOptimizedFrameLayout

CollapsedStatusBarFragment.java

public void initNotificationIconArea(NotificationIconAreaControllernotificationIconAreaController) {ViewGroup notificationIconArea = mStatusBar.findViewById(R.id.notification_icon_area);mNotificationIconAreaInner =notificationIconAreaController.getNotificationInnerAreaView();if (mNotificationIconAreaInner.getParent() != null) {((ViewGroup) mNotificationIconAreaInner.getParent()).removeView(mNotificationIconAreaInner);}notificationIconArea.addView(mNotificationIconAreaInner);// Default to showing until we know otherwise.showNotificationIconArea(false);}

NotificationIconAreaController.java

/*** Initializes the views that will represent the notification area.*/protected void initializeNotificationAreaViews(Context context) {reloadDimens(context);LayoutInflater layoutInflater = LayoutInflater.from(context);mNotificationIconArea = inflateIconArea(layoutInflater);mNotificationIcons = (NotificationIconContainer) mNotificationIconArea.findViewById(R.id.notificationIcons);mNotificationScrollLayout = mStatusBar.getNotificationScrollLayout();}protected View inflateIconArea(LayoutInflater inflater) {return inflater.inflate(R.layout.notification_icon_area, null);}

如上,我们就找到了初始化的地方,主要是通过inflate这个R.layout.notification_icon_area文件,通过addView的方式添加到了AlphaOptimizedFrameLayout,下面就是看下R.layout.notification_icon_area这个文件了

<com.android.keyguard.AlphaOptimizedLinearLayoutxmlns:android="http://schemas.android.com/apk/res/android"android:id="@+id/notification_icon_area_inner"android:layout_width="match_parent"android:layout_height="match_parent" ><com.android.systemui.statusbar.phone.NotificationIconContainerandroid:id="@+id/notificationIcons"android:layout_width="match_parent"android:layout_height="match_parent"android:layout_alignParentStart="true"android:gravity="center_vertical"android:orientation="horizontal"/>
</com.android.keyguard.AlphaOptimizedLinearLayout>

/*** A container for notification icons. It handles overflowing icons properly and positions them* correctly on the screen.*/
public class NotificationIconContainer extends AlphaOptimizedFrameLayout {}

从备注就能够看出来,这个就是所有notification icons的父控件,所有icons最后都是添加到这里面来的,
好了，到这里我们的第一部分初始化流程就讲完了。

通知icon显示流程

首先我们需要看下notification生成的地方

StatusBar.java

public void onNotificationPosted(final StatusBarNotification sbn,final RankingMap rankingMap) {if (isUpdate) {updateNotification(sbn, rankingMap);} else {addNotification(sbn, rankingMap);}
}public void addNotification(StatusBarNotification notification, RankingMap ranking)throws InflationException {String key = notification.getKey();if (DEBUG) Log.d(TAG, "addNotification key=" + key);mNotificationData.updateRanking(ranking);Entry shadeEntry = createNotificationViews(notification);protected NotificationData.Entry createNotificationViews(StatusBarNotification sbn)throws InflationException {if (DEBUG) {Log.d(TAG, "createNotificationViews(notification=" + sbn);}NotificationData.Entry entry = new NotificationData.Entry(sbn);Dependency.get(LeakDetector.class).trackInstance(entry);entry.createIcons(mContext, sbn);// Construct the expanded view.inflateViews(entry, mStackScroller);return entry;}
}

层层调用之后,最后会通过entry.createIcons(mContext, sbn)生成notification icon,然后存放在NotificationData里面,感兴趣的可以看下entry.createIcons(mContext, sbn), 该函数里面主要生成了一个StatusBarIconView对象,这个就是最终显示在状态栏的icon。

notification生成的过程大致就是通过inflateViews(entry, mStackScroller)--->AsyncInflationTask处理加载然后生成ExpandableNotificationRow等的信息,最后通过StatusBar.java

@Overridepublic void onAsyncInflationFinished(Entry entry) {mPendingNotifications.remove(entry.key);// If there was an async task started after the removal, we don't want to add it back to// the list, otherwise we might get leaks.boolean isNew = mNotificationData.get(entry.key) == null;if (isNew && !entry.row.isRemoved()) {addEntry(entry);} else if (!isNew && entry.row.hasLowPriorityStateUpdated()) {mVisualStabilityManager.onLowPriorityUpdated(entry);updateNotificationShade();//  此处完成添加}entry.row.setLowPriorityStateUpdated(false);}private void updateNotificationShade() {................................................for (int i=0; i<toShow.size(); i++) {View v = toShow.get(i);if (v.getParent() == null) {mVisualStabilityManager.notifyViewAddition(v);mStackScroller.addView(v);}}................................................// Let's also update the iconsmNotificationIconAreaController.updateNotificationIcons(mNotificationData);//添加notification icons
}

updateNotificationShade这个函数回调完成view的添加,这个函数先是把inflate出来的通知,添加到NotificationScrollLayout里面,然后再添加notification icon,接下来我们就看下updateNotificationIcons里面的逻辑了。

NotificationIconAreaController.java

private NotificationIconContainer mNotificationIcons;
/*** Updates the notifications with the given list of notifications to display.*/public void updateNotificationIcons(NotificationData notificationData) {updateIconsForLayout(notificationData, entry -> entry.icon, mNotificationIcons,false /* showAmbient */);//  添加status bar notification iconupdateIconsForLayout(notificationData, entry -> entry.expandedIcon, mShelfIcons,NotificationShelf.SHOW_AMBIENT_ICONS);//  添加 notification self iconapplyNotificationIconsTint();}

主要的添加动作就在updateIconsForLayout这个函数中了

private void updateIconsForLayout(NotificationData notificationData,Function<NotificationData.Entry, StatusBarIconView> function,NotificationIconContainer hostLayout, boolean showAmbient) {ArrayList<StatusBarIconView> toShow = new ArrayList<>(mNotificationScrollLayout.getChildCount());// Filter out ambient notifications and notification children.for (int i = 0; i < mNotificationScrollLayout.getChildCount(); i++) {View view = mNotificationScrollLayout.getChildAt(i);if (view instanceof ExpandableNotificationRow) {NotificationData.Entry ent = ((ExpandableNotificationRow) view).getEntry();if (shouldShowNotificationIcon(ent, notificationData, showAmbient)) {toShow.add(function.apply(ent));}}}..................................................................................................................final FrameLayout.LayoutParams params = generateIconLayoutParams();for (int i = 0; i < toShow.size(); i++) {View v = toShow.get(i);// The view might still be transiently added if it was just removed and added againhostLayout.removeTransientView(v);if (v.getParent() == null) {hostLayout.addView(v, i, params);}}}

首先从mNotificationScrollLayout取出NotificationData,然后把NotificationData存放的StatusBarIconView取出添加到toShow里面,最后遍历添加到NotificationIconContainer中,这样就完成了往NotificationIconContainer添加icon的过程。

到这里，notification icon加载流程已经讲完，后面有时间还会讲下signal icon的加载流程，敬请关注。