Android 4.0 ICS SystemUI浅析——StatusBar加载流程之Notification

前面三篇文章《Android 4.0 ICS SystemUI浅析——SystemUI启动流程》、《Android
4.0 ICS SystemUI浅析——StatusBar结构分析》、《Android 4.0 ICS SystemUI浅析——StatusBar加载流程分析》逐步分析了SystemUI中StatusBar的启动以及加载流程，本文主要分析StatusBar上的Notification的加载，如有不正之处还恳请各位帮忙指正。

本文来自：http://blog.csdn.net/yihongyuelan 欢迎转载 请务必注明出处！

在上一篇文章《Android 4.0 ICS SystemUI浅析——StatusBar加载流程分析》中，我们主要分析了StatusBar上的系统Icons加载的过程，包括了耳机图标、蓝牙图标、禁音图标等等，此文是紧接着上文分析的，因此我们首先看到/SourceCode/frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/StatusBar.java的start()：

[java] view
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public void start() {

// First set up our views and stuff.首先准备我们需要显示的view以及原材料

//我们先跟踪这里的makeStatusBarView

View sb = makeStatusBarView();

// Connect in to the status bar manager service

//初始化各个存储器，用于存储各类信息，这些信息通过StatusBarManagerService获取

//iconsList用于存放icons

StatusBarIconList iconList = new StatusBarIconList();

//nodificationKeys保存以Binder为Key的notification

ArrayList<IBinder> notificationKeys = new ArrayList<IBinder>();

//保存StatusBarNotification类型的notifications

ArrayList<StatusBarNotification> notifications = new ArrayList<StatusBarNotification>();

//mCommandQueue是和IStatusBarService进行交互的IBinder

mCommandQueue = new CommandQueue(this, iconList);

//这里实际上获取的是StatusBarManagerService

mBarService = IStatusBarService.Stub.asInterface(

ServiceManager.getService(Context.STATUS_BAR_SERVICE));

int[] switches = new int[7];

ArrayList<IBinder> binders = new ArrayList<IBinder>();

try {

//通过StatusBarManagerService中的registerStatusBar来获取初始设置

mBarService.registerStatusBar(mCommandQueue, iconList, notificationKeys, notifications,

switches, binders);

} catch (RemoteException ex) {

// If the system process isn't there we're doomed anyway.

}

... ...

// Set up the initial notification state

//加载notifications，本文的分析主要从这里开始！

N = notificationKeys.size();

if (N == notifications.size()) {

for (int i=0; i<N; i++) {

addNotification(notificationKeys.get(i), notifications.get(i));

}

} else {

Log.wtf(TAG, "Notification list length mismatch: keys=" + N

+ " notifications=" + notifications.size());

}

... ...

lp.gravity = getStatusBarGravity();

lp.setTitle("StatusBar");

lp.packageName = mContext.getPackageName();

lp.windowAnimations = R.style.Animation_StatusBar;

//在Window上显示StatusBar界面

WindowManagerImpl.getDefault().addView(sb, lp);

mDoNotDisturb = new DoNotDisturb(mContext);

}

我们可以看到addNotification()方法主要完成Notification图标的加载。跟进去看看(因为我们分析的是Phone因此选择PhoneStatusBar)，代码如下：

[java] view
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public void addNotification(IBinder key, StatusBarNotification notification) {

//该方法主要构造Notification Icons以及Expaned View

StatusBarIconView iconView = addNotificationViews(key, notification);

if (iconView == null) return;

boolean immersive = false;

try {

//判断当前栈顶Activity是否具有android:immersive属性。该属性在Android 4.0中新加入的属性，如果该属性为true则该Activity不能被其他Activity或者Notification所打断。

immersive = ActivityManagerNative.getDefault().isTopActivityImmersive();

if (DEBUG) {

Slog.d(TAG, "Top activity is " + (immersive?"immersive":"not immersive"));

}

} catch (RemoteException ex) {

}

//因为这里我们返回的是false，所以不会执行

if (immersive) {

if ((notification.notification.flags & Notification.FLAG_HIGH_PRIORITY) != 0) {

Slog.d(TAG, "Presenting high-priority notification in immersive activity");

// special new transient ticker mode

// 1. Populate mIntruderAlertView

ImageView alertIcon = (ImageView) mIntruderAlertView.findViewById(R.id.alertIcon);

TextView alertText = (TextView) mIntruderAlertView.findViewById(R.id.alertText);

alertIcon.setImageDrawable(StatusBarIconView.getIcon(

alertIcon.getContext(),

iconView.getStatusBarIcon()));

alertText.setText(notification.notification.tickerText);

View button = mIntruderAlertView.findViewById(R.id.intruder_alert_content);

button.setOnClickListener(

new NotificationClicker(notification.notification.contentIntent,

notification.pkg, notification.tag, notification.id));

// 2. Animate mIntruderAlertView in

mHandler.sendEmptyMessage(MSG_SHOW_INTRUDER);

// 3. Set alarm to age the notification off (TODO)

mHandler.removeMessages(MSG_HIDE_INTRUDER);

mHandler.sendEmptyMessageDelayed(MSG_HIDE_INTRUDER, INTRUDER_ALERT_DECAY_MS);

}

//这里的fullScreenIntent=null因此也不执行

} else if (notification.notification.fullScreenIntent != null) {

// not immersive & a full-screen alert should be shown

Slog.d(TAG, "Notification has fullScreenIntent; sending fullScreenIntent");

try {

notification.notification.fullScreenIntent.send();

} catch (PendingIntent.CanceledException e) {

}

} else {

// usual case: status bar visible & not immersive

// show the ticker

//因此StatusBar可见同时不具有immersive属性，因此显示tiker

tick(notification);

}

// Recalculate the position of the sliding windows and the titles.

// 重新计算滑动窗口的位置和标题

setAreThereNotifications();

// 更新ExpanedView

updateExpandedViewPos(EXPANDED_LEAVE_ALONE);

}

通过对以上代码的分析，我们可以大致知道，Notification的加载主要分为三步：

1.addNotificationViews(key, notification);

2.tick(notification);

3.setAreThereNotifications()和updateExpandedViewPos(EXPANDED_LEAVE_ALONE);

那么接下来我们就通过这三个方法来分析Notification的加载。

(1). addNotificationViews(key, notification);

跟踪查看代码如下：

[java] view
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StatusBarIconView addNotificationViews(IBinder key, StatusBarNotification notification) {

if (DEBUG) {

Slog.d(TAG, "addNotificationViews(key=" + key + ", notification=" + notification);

}

// Construct the icon.

// 初始化iconView

final StatusBarIconView iconView = new StatusBarIconView(mContext,

notification.pkg + "/0x" + Integer.toHexString(notification.id),

notification.notification);

//设置icons按照什么方式显示

iconView.setScaleType(ImageView.ScaleType.CENTER_INSIDE);

// 对全局变量赋值

final StatusBarIcon ic = new StatusBarIcon(notification.pkg,

notification.notification.icon,

notification.notification.iconLevel,

notification.notification.number,

notification.notification.tickerText);

// 设置显示icons 和上一篇文章提到的系统icons图标设置是一样的 如果返回true则表示设置成功

if (!iconView.set(ic)) {

handleNotificationError(key, notification, "Couldn't create icon: " + ic);

return null;

}

// Construct the expanded view.

// 将Notification在ExpandedView上显示出来

NotificationData.Entry entry = new NotificationData.Entry(key, notification, iconView);

if (!inflateViews(entry, mPile)) {

handleNotificationError(key, notification, "Couldn't expand RemoteViews for: "

+ notification);

return null;

}

// Add the expanded view and icon.

//mNotificationData中保存着当前显示的Notification的数量及其属性

int pos = mNotificationData.add(entry);

if (DEBUG) {

Slog.d(TAG, "addNotificationViews: added at " + pos);

}

//更新图标

updateNotificationIcons();

return iconView;

}

根据以上代码，我们可以知道在addNotificationViews()中，又可以细分为三步：设置icons，设置ExpanedView，更新图标。其中，设置icons实际上和上一篇文章中设置系统Icons类似。主要区别在设置ExpandedView和更新图标。那跟踪inflateViews()方法可以看到：

[java] view
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private boolean inflateViews(NotificationData.Entry entry, ViewGroup parent) {

StatusBarNotification sbn = entry.notification;

//初始化remoteViews(如果有过自定义Notification经验的朋友肯定对这个很熟悉，不了解的朋友可以自己去试试)

RemoteViews remoteViews = sbn.notification.contentView;

if (remoteViews == null) {

return false;

}

// create the row view

LayoutInflater inflater = (LayoutInflater)mContext.getSystemService(

Context.LAYOUT_INFLATER_SERVICE);

// 加载布局文件，默认的通知信息在ExpandedView中是以一行来显示的，左侧是图标，右侧是通知标题和内容

View row = inflater.inflate(R.layout.status_bar_notification_row, parent, false);

//这个所谓的button实际上是在清除单个通知信息时调用的

View vetoButton = updateNotificationVetoButton(row, sbn);

//设置vetoButton的备注说明，作为一种辅助功能提供,为一些没有文字描述的View提供说明。这在界面上不会有效果，可临时放一点字符串数据

vetoButton.setContentDescription(mContext.getString(

R.string.accessibility_remove_notification));

// the large icon

//如果有largeIcon则进行设置。这里提到的largeIcon我也不知道具体用处是什么

ImageView largeIcon = (ImageView)row.findViewById(R.id.large_icon);

if (sbn.notification.largeIcon != null) {

largeIcon.setImageBitmap(sbn.notification.largeIcon);

largeIcon.setContentDescription(sbn.notification.tickerText);

} else {

largeIcon.getLayoutParams().width = 0;

largeIcon.setVisibility(View.INVISIBLE);

}

largeIcon.setContentDescription(sbn.notification.tickerText);

// bind the click event to the content area

ViewGroup content = (ViewGroup)row.findViewById(R.id.content);

// XXX: update to allow controls within notification views

content.setDescendantFocusability(ViewGroup.FOCUS_BLOCK_DESCENDANTS);

// content.setOnFocusChangeListener(mFocusChangeListener);

PendingIntent contentIntent = sbn.notification.contentIntent;

if (contentIntent != null) {

//绑定largIcons和content区域的点击事件

final View.OnClickListener listener = new NotificationClicker(contentIntent,

sbn.pkg, sbn.tag, sbn.id);

largeIcon.setOnClickListener(listener);

content.setOnClickListener(listener);

} else {

largeIcon.setOnClickListener(null);

content.setOnClickListener(null);

}

View expanded = null;

Exception exception = null;

try {

// Inflates视图对象并且应用到所有的动作中

expanded = remoteViews.apply(mContext, content);

}

catch (RuntimeException e) {

exception = e;

}

if (expanded == null) {

final String ident = sbn.pkg + "/0x" + Integer.toHexString(sbn.id);

Slog.e(TAG, "couldn't inflate view for notification " + ident, exception);

return false;

} else {

//content 添加显示view

content.addView(expanded);

// 获取view中的图像前需要设为true

row.setDrawingCacheEnabled(true);

}

// 设置这些通知信息原始背景

applyLegacyRowBackground(sbn, content);

// 将设置好的属性回传给entry

entry.row = row;

entry.content = content;

entry.expanded = expanded;

entry.largeIcon = largeIcon;

return true;

}

对于ExpanedView中的Notification设置，可能这里有点模糊，那请看以下图1和图2：



图 1



图2

通过图1和图2我们可以看到largeIcon以及vetoButton触发时间。对于ExpandedView，后面会有较为详细的分析。

上面分析了ExpandedView中的Notification的设置，在addNotificationViews(key, notification);中就还剩下最后一个步骤了，即更新图标，那么查看addNotificationView()中的updateNotificationIcons()方法，代码如下：

[java] view
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private void updateNotificationIcons() {

// 该方法主要用于将通知信息在ExpandedView中显示 如果注释掉则通知将不会在ExpandedView中显示

loadNotificationShade();

// 下面的操作主要完成在StatusBar添加通知提示图标

final LinearLayout.LayoutParams params

= new LinearLayout.LayoutParams(mIconSize + 2*mIconHPadding, mNaturalBarHeight);

int N = mNotificationData.size();

if (DEBUG) {

Slog.d(TAG, "refreshing icons: " + N + " notifications, mNotificationIcons=" + mNotificationIcons);

}

ArrayList<View> toShow = new ArrayList<View>();

for (int i=0; i<N; i++) {

toShow.add(mNotificationData.get(N-i-1).icon);

}

ArrayList<View> toRemove = new ArrayList<View>();

for (int i=0; i<mNotificationIcons.getChildCount(); i++) {

View child = mNotificationIcons.getChildAt(i);

if (!toShow.contains(child)) {

toRemove.add(child);

}

}

for (View remove : toRemove) {

mNotificationIcons.removeView(remove);

}

for (int i=0; i<toShow.size(); i++) {

View v = toShow.get(i);

if (v.getParent() == null) {

mNotificationIcons.addView(v, i, params);

}

}

}

通过以上代码的分析，我们可以知道updateNotificationIcons()主要做了两件事：更新ExpanddeView上的通知信息；更新StatusBar上的通知图标。更新方法都类似，先查通知看是否有效，如果不是则删除，如果是则添加。以上完成了加载Notification的第一步，那么我来看第二步tick(notification)。

(2).tick(notification)，跟踪代码如下：

[java] view
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private void tick(StatusBarNotification n) {

// Show the ticker if one is requested. Also don't do this

// until status bar window is attached to the window manager,

// because... well, what's the point otherwise? And trying to

// run a ticker without being attached will crash!

if (n.notification.tickerText != null && mStatusBarView.getWindowToken() != null) {

if (0 == (mDisabled & (StatusBarManager.DISABLE_NOTIFICATION_ICONS

| StatusBarManager.DISABLE_NOTIFICATION_TICKER))) {

//ticker执行方法

mTicker.addEntry(n);

}

}

}

跳转到mTicker.addEntry();方法中，代码路径：SourceCode/frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone/Ticker.java中，代码如下：

[java] view
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public void addEntry(StatusBarNotification n) {

int initialCount = mSegments.size();

// If what's being displayed has the same text and icon, just drop it

// (which will let the current one finish, this happens when apps do

// a notification storm).

if (initialCount > 0) {

final Segment seg = mSegments.get(0);

//判断该Notififacation是不是已经在StatusBar上显示了的(同一个Notification发送两次这里并么有执行，为什么？)

if (n.pkg.equals(seg.notification.pkg)

&& n.notification.icon == seg.notification.notification.icon

&& n.notification.iconLevel == seg.notification.notification.iconLevel

&& CharSequences.equals(seg.notification.notification.tickerText,

n.notification.tickerText)) {

return;

}

}

// 获取该Notification的icon

final Drawable icon = StatusBarIconView.getIcon(mContext,

new StatusBarIcon(n.pkg, n.notification.icon, n.notification.iconLevel, 0,

n.notification.tickerText));

// 将Notification的一些信息放入对象newSegment中，这里的Segment翻译过来是片段和部分的意思

// Segment是Ticker类的内部类，用于存放notification的部分信息以及对信息的一些处理，比如tickerText

final Segment newSegment = new Segment(n, icon, n.notification.tickerText);

// If there's already a notification schedule for this package and id, remove it.

// 若果该信息在Segment中已经存在，则删除掉

for (int i=0; i<mSegments.size(); i++) {

Segment seg = mSegments.get(i);

if (n.id == seg.notification.id && n.pkg.equals(seg.notification.pkg)) {

// just update that one to use this new data instead(什么时候触发？)

mSegments.remove(i--); // restart iteration here

}

}

// 将Notification的部分信息放到mSegments链表中。

mSegments.add(newSegment);

if (initialCount == 0 && mSegments.size() > 0) {

Segment seg = mSegments.get(0);

seg.first = false;

//初始化id/tickerIcon

mIconSwitcher.setAnimateFirstView(false);

mIconSwitcher.reset();

mIconSwitcher.setImageDrawable(seg.icon);

//初始化id/tickerText

mTextSwitcher.setAnimateFirstView(false);

mTextSwitcher.reset();

mTextSwitcher.setText(seg.getText());

//启动ticker

tickerStarting();

scheduleAdvance();

}

}

通过Open Implementation我们跳转到PhoneStatusBar中的tickerStatrting()中，代码如下：

[java] view
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@Override

public void tickerStarting() {

mTicking = true;

//这里的mIcons和ticker组成了整个StatusBar的布局，因此这里要线将它置为GONE

mIcons.setVisibility(View.GONE);

//显示tickerText

mTickerView.setVisibility(View.VISIBLE);

//加载ticker弹出时的动画

mTickerView.startAnimation(loadAnim(com.android.internal.R.anim.push_up_in, null));

mIcons.startAnimation(loadAnim(com.android.internal.R.anim.push_up_out, null));

}

这里可以发现ticker开加载动画并显示了，实际上Notification在StatusBar上的显示效果是加载了动画的原因。继续查看scheduleAdvance()方法：

[java] view
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private void scheduleAdvance() {

mHandler.postDelayed(mAdvanceTicker, TICKER_SEGMENT_DELAY);

}

通过Handler的PostDelay方法执行mAdvanceTicker这个Runnable中的run方法，代码如下：

[java] view
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private Runnable mAdvanceTicker = new Runnable() {

public void run() {

while (mSegments.size() > 0) {

Segment seg = mSegments.get(0);

if (seg.first) {

// this makes the icon slide in for the first one for a given

// notification even if there are two notifications with the

// same icon in a row

// 第一次显示时，设置tickerIcon的值，这里就是ticker最前方显示的那个icon

mIconSwitcher.setImageDrawable(seg.icon);

}

CharSequence text = seg.advance();

if (text == null) {

mSegments.remove(0);

continue;

}

// 显示用户设置的tickerText内容

mTextSwitcher.setText(text);

scheduleAdvance();

break;

}

if (mSegments.size() == 0) {

// 完成ticker的一次显示

tickerDone();

}

}

};

最后我们再来看看tickerDone()方法，该方法主要对应于tickerStarting()方法，代码如下：

[java] view
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@Override

public void tickerDone() {

//显示mIcons布局

mIcons.setVisibility(View.VISIBLE);

//tickerText消失

mTickerView.setVisibility(View.GONE);

//加载ticker消失的动画

mIcons.startAnimation(loadAnim(com.android.internal.R.anim.push_down_in, null));

mTickerView.startAnimation(loadAnim(com.android.internal.R.anim.push_down_out,

mTickingDoneListener));

}

至此，我们完成了Notification加载的前两步，分别是addNotificationViews(key, notification)和tick(notification)。剩下最后一步，即：setAreThereNotifications()和updateExpandedViewPos(EXPANDED_LEAVE_ALONE);

(3).setAreThereNotifications()和updateExpandedViewPos().这里先说一下setAreThereNotifications()方法，代码如下：

[java] view
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private void setAreThereNotifications() {

//是否有Notification

final boolean any = mNotificationData.size() > 0;

//该Notification是否可被清除

final boolean clearable = any && mNotificationData.hasClearableItems();

if (DEBUG) {

Slog.d(TAG, "setAreThereNotifications: N=" + mNotificationData.size()

+ " any=" + any + " clearable=" + clearable);

}

//对"清除所有通知"按钮进行设置

if (mClearButton.isShown()) {

if (clearable != (mClearButton.getAlpha() == 1.0f)) {

ObjectAnimator.ofFloat(mClearButton, "alpha",

clearable ? 1.0f : 0.0f)

.setDuration(250)

.start();

}

} else {

mClearButton.setAlpha(clearable ? 1.0f : 0.0f);

}

mClearButton.setEnabled(clearable);

...

}

继续分析updateExpandedViewPos(EXPANDED_LEAVE_ALONE);方法，代码如下；

[java] view
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void updateExpandedViewPos(int expandedPosition) {

if (SPEW) {

Slog.d(TAG, "updateExpandedViewPos before expandedPosition=" + expandedPosition

+ " mTrackingParams.y=" + ((mTrackingParams == null) ? "?" : mTrackingParams.y)

+ " mTrackingPosition=" + mTrackingPosition);

}

//获取StatusBar高度

int h = mStatusBarView.getHeight();

//获取当前分辨率高度

int disph = mDisplayMetrics.heightPixels;

// If the expanded view is not visible, make sure they're still off screen.

// Maybe the view was resized.

//如果ExpanedView不可见则执行

if (!mExpandedVisible) {

//更新mTrackingView属性，设置mExpandedDialog属性

updateExpandedInvisiblePosition();

return;

}

// tracking view...

//设置TriackingView的各种属性

int pos;

if (expandedPosition == EXPANDED_FULL_OPEN) {

pos = h;

}

else if (expandedPosition == EXPANDED_LEAVE_ALONE) {

//传递参数为EXPANDED_LEAVE_ALONE

pos = mTrackingPosition;

}

else {

if (expandedPosition <= disph) {

pos = expandedPosition;

} else {

pos = disph;

}

pos -= disph-h;

}

mTrackingPosition = mTrackingParams.y = pos;

mTrackingParams.height = disph-h;

WindowManagerImpl.getDefault().updateViewLayout(mTrackingView, mTrackingParams);

if (mExpandedParams != null) {

if (mCloseView.getWindowVisibility() == View.VISIBLE) {

mCloseView.getLocationInWindow(mPositionTmp);

final int closePos = mPositionTmp[1];

mExpandedContents.getLocationInWindow(mPositionTmp);

final int contentsBottom = mPositionTmp[1] + mExpandedContents.getHeight();

mExpandedParams.y = pos + mTrackingView.getHeight()

- (mTrackingParams.height-closePos) - contentsBottom;

if (SPEW) {

Slog.d(PhoneStatusBar.TAG,

"pos=" + pos +

" trackingHeight=" + mTrackingView.getHeight() +

" (trackingParams.height - closePos)=" +

(mTrackingParams.height - closePos) +

" contentsBottom=" + contentsBottom);

}

} else {

// If the tracking view is not yet visible, then we can't have

// a good value of the close view location. We need to wait for

// it to be visible to do a layout.

mExpandedParams.y = -mDisplayMetrics.heightPixels;

}

int max = h;

if (mExpandedParams.y > max) {

mExpandedParams.y = max;

}

int min = mTrackingPosition;

if (mExpandedParams.y < min) {

mExpandedParams.y = min;

}

boolean visible = (mTrackingPosition + mTrackingView.getHeight()) > h;

if (!visible) {

// if the contents aren't visible, move the expanded view way off screen

// because the window itself extends below the content view.

mExpandedParams.y = -disph;

}

mExpandedDialog.getWindow().setAttributes(mExpandedParams);

// As long as this isn't just a repositioning that's not supposed to affect

// the user's perception of what's showing, call to say that the visibility

// has changed. (Otherwise, someone else will call to do that).

if (expandedPosition != EXPANDED_LEAVE_ALONE) {

if (SPEW) Slog.d(TAG, "updateExpandedViewPos visibilityChanged(" + visible + ")");

visibilityChanged(visible);

}

}

if (SPEW) {

Slog.d(TAG, "updateExpandedViewPos after expandedPosition=" + expandedPosition

+ " mTrackingParams.y=" + mTrackingParams.y

+ " mTrackingPosition=" + mTrackingPosition

+ " mExpandedParams.y=" + mExpandedParams.y

+ " mExpandedParams.height=" + mExpandedParams.height);

}

}

以上代码主要完成对TrackingView的属性设置，ExpandedView实际上是包裹在TrackingView中的，因此这里也附带进行了设置，最后更新，完成了整个Notification的加载。

小结

通过对Notification加载流程的分析，对Notifification工作流程有了大致的了解。针对上文中的分析可能部分地方还有所偏颇，还需要加强自己的代码阅读能力。以下是简单的时序图，如图3：



图3