SystemUI之状态栏notification icon加载流程

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

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(NotificationIconAreaController
            notificationIconAreaController) {
        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

/**
 * 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

@Override
    public 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

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 icon
        updateIconsForLayout(notificationData, entry -> entry.expandedIcon, mShelfIcons,
                NotificationShelf.SHOW_AMBIENT_ICONS);//  添加 notification self icon

        applyNotificationIconsTint();
    }

主要的添加动作就在updateIconsForLayout这个函数中了

private void updateIconsForLayout(NotificationData notificationData,
            Function function,
            NotificationIconContainer hostLayout, boolean showAmbient) {

        ArrayList 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 again
            hostLayout.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。

如有什么问题欢迎指正。

本文章已经独家授权ApeClub公众号使用。