前言
通知可以說是Android系統最常見的功能之一，大多數應用處于背景收到服務端推送消息的時候，都會觸發系統狀态欄通知來提醒使用者特定的資訊，而NotificationManagerService作為通知服務，和系統通知功能息息相關，要了解NotificationManagerService服務，自然要先知道它是如何誕生的，本篇文章我們将會具體梳理一下NotificationManagerService的啟動流程。
一、SystemServer啟動NotificationManagerService的服務
1、系統啟動後會啟動JVM虛拟機，SystemServer 是虛拟機的第一個程序，由init 程序fork 産生。主要用來啟動frameworks層中的服務。SystemServer程序裡面有個main()方法，main 方法如下：
frameworks/base/service/java/com/android/server/SystemServer.java
public final class SystemServer {
public static void main(String[] args) {
new SystemServer().run();
}
}
2、main 方法裡啟動了 run() 方法，而在 run 方法中調用了startOtherServices() 方法：
public final class SystemServer {
private void run() {
...
// Start services.
try {
traceBeginAndSlog("StartServices");
startBootstrapServices();//啟動引導服務
startCoreServices();//啟動核心服務
startOtherServices();//啟動其他服務
SystemServerInitThreadPool.shutdown();
} catch (Throwable ex) {
Slog.e("System", "******************************************");
Slog.e("System", "************ Failure starting system services", ex);
throw ex;
} finally {
traceEnd();
}
...
}
}
3、startOtherServices方法和NotificationManagerService服務啟動相關的代碼如下所示。
public final class SystemServer {
private SystemServiceManager mSystemServiceManager;
private ActivityManagerService mActivityManagerService;
private void startOtherServices(@NonNull TimingsTraceAndSlog t) {
...代碼省略...
traceBeginAndSlog("StartNotificationManager");
mSystemServiceManager.startService(NotificationManagerService.class);
SystemNotificationChannels.createAll(context);
notification = INotificationManager.Stub.asInterface(
ServiceManager.getService(Context.NOTIFICATION_SERVICE));
traceEnd();
...代碼省略...
}
}
4、SystemServiceManager的startService方法如下所示：
frameworks/base/services/core/java/com/android/server/SystemServiceManager.java
public class SystemServiceManager {
/**
* Creates and starts a system service. The class must be a subclass of
* {@link com.android.server.SystemService}.
*
* @param serviceClass A Java class that implements the SystemService interface.
* @return The service instance, never null.
* @throws RuntimeException if the service fails to start.
*/
@SuppressWarnings("unchecked")
public <T extends SystemService> T startService(Class<T> serviceClass) {
try {
final String name = serviceClass.getName();
Slog.i(TAG, "Starting " + name);
Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, "StartService " + name);
// Create the service.
if (!SystemService.class.isAssignableFrom(serviceClass)) {
throw new RuntimeException("Failed to create " + name
+ ": service must extend " + SystemService.class.getName());
}
final T service;
try {
Constructor<T> constructor = serviceClass.getConstructor(Context.class);
service = constructor.newInstance(mContext);
} catch (InstantiationException ex) {
throw new RuntimeException("Failed to create service " + name
+ ": service could not be instantiated", ex);
} catch (IllegalAccessException ex) {
throw new RuntimeException("Failed to create service " + name
+ ": service must have a public constructor with a Context argument", ex);
} catch (NoSuchMethodException ex) {
throw new RuntimeException("Failed to create service " + name
+ ": service must have a public constructor with a Context argument", ex);
} catch (InvocationTargetException ex) {
throw new RuntimeException("Failed to create service " + name
+ ": service constructor threw an exception", ex);
}
startService(service);
return service;
} finally {
Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);
}
}
public void startService(@NonNull final SystemService service) {
// Register it.
mServices.add(service);
// Start it.
long time = SystemClock.elapsedRealtime();
try {
service.onStart();
} catch (RuntimeException ex) {
throw new RuntimeException("Failed to start service " + service.getClass().getName()
+ ": onStart threw an exception", ex);
}
warnIfTooLong(SystemClock.elapsedRealtime() - time, service, "onStart");
}
}
startService方法首先通過反射建立了NotificationManagerService對象，緊接着會調用NotificationManagerService的onStart方法。
二、NotificationManagerService啟動
1、NotificationManagerService的onStart方法如下所示：
frameworks/base/services/core/java/com/android/server/notification/NotificationManagerService.java
public class NotificationManagerService extends SystemService {
@Override
public void onStart() {
SnoozeHelper snoozeHelper = new SnoozeHelper(getContext(), new SnoozeHelper.Callback() {
@Override
public void repost(int userId, NotificationRecord r) {
try {
if (DBG) {
Slog.d(TAG, "Reposting " + r.getKey());
}
enqueueNotificationInternal(r.sbn.getPackageName(), r.sbn.getOpPkg(),
r.sbn.getUid(), r.sbn.getInitialPid(), r.sbn.getTag(), r.sbn.getId(),
r.sbn.getNotification(), userId);
} catch (Exception e) {
Slog.e(TAG, "Cannot un-snooze notification", e);
}
}
}, mUserProfiles);
final File systemDir = new File(Environment.getDataDirectory(), "system");
//調用init方法，賦予目前線程的looper對象給init方法
init(Looper.myLooper(),
AppGlobals.getPackageManager(), getContext().getPackageManager(),
getLocalService(LightsManager.class),
new NotificationListeners(AppGlobals.getPackageManager()),
new NotificationAssistants(getContext(), mNotificationLock, mUserProfiles,
AppGlobals.getPackageManager()),
new ConditionProviders(getContext(), mUserProfiles, AppGlobals.getPackageManager()),
null, snoozeHelper, new NotificationUsageStats(getContext()),
new AtomicFile(new File(systemDir, "notification_policy.xml"), "notification-policy"),
(ActivityManager) getContext().getSystemService(Context.ACTIVITY_SERVICE),
getGroupHelper(), ActivityManager.getService(),
LocalServices.getService(UsageStatsManagerInternal.class),
LocalServices.getService(DevicePolicyManagerInternal.class));
//注冊廣播接收者，監聽系統事件
// register for various Intents
IntentFilter filter = new IntentFilter();
filter.addAction(Intent.ACTION_SCREEN_ON);//螢幕亮
filter.addAction(Intent.ACTION_SCREEN_OFF);//螢幕滅
filter.addAction(TelephonyManager.ACTION_PHONE_STATE_CHANGED);
filter.addAction(Intent.ACTION_USER_PRESENT);
filter.addAction(Intent.ACTION_USER_STOPPED);
filter.addAction(Intent.ACTION_USER_SWITCHED);
filter.addAction(Intent.ACTION_USER_ADDED);
filter.addAction(Intent.ACTION_USER_REMOVED);
filter.addAction(Intent.ACTION_USER_UNLOCKED);
filter.addAction(Intent.ACTION_MANAGED_PROFILE_UNAVAILABLE);
getContext().registerReceiver(mIntentReceiver, filter);
//注冊廣播接收者，監聽應用包名的各種變化
IntentFilter pkgFilter = new IntentFilter();
pkgFilter.addAction(Intent.ACTION_PACKAGE_ADDED);
pkgFilter.addAction(Intent.ACTION_PACKAGE_REMOVED);
pkgFilter.addAction(Intent.ACTION_PACKAGE_CHANGED);
pkgFilter.addAction(Intent.ACTION_PACKAGE_RESTARTED);
pkgFilter.addAction(Intent.ACTION_QUERY_PACKAGE_RESTART);
pkgFilter.addDataScheme("package");
getContext().registerReceiverAsUser(mPackageIntentReceiver, UserHandle.ALL, pkgFilter, null,
null);
IntentFilter suspendedPkgFilter = new IntentFilter();
suspendedPkgFilter.addAction(Intent.ACTION_PACKAGES_SUSPENDED);
suspendedPkgFilter.addAction(Intent.ACTION_PACKAGES_UNSUSPENDED);
getContext().registerReceiverAsUser(mPackageIntentReceiver, UserHandle.ALL,
suspendedPkgFilter, null, null);
IntentFilter sdFilter = new IntentFilter(Intent.ACTION_EXTERNAL_APPLICATIONS_UNAVAILABLE);
getContext().registerReceiverAsUser(mPackageIntentReceiver, UserHandle.ALL, sdFilter, null,
null);
IntentFilter timeoutFilter = new IntentFilter(ACTION_NOTIFICATION_TIMEOUT);
timeoutFilter.addDataScheme(SCHEME_TIMEOUT);
getContext().registerReceiver(mNotificationTimeoutReceiver, timeoutFilter);
IntentFilter settingsRestoredFilter = new IntentFilter(Intent.ACTION_SETTING_RESTORED);
getContext().registerReceiver(mRestoreReceiver, settingsRestoredFilter);
IntentFilter localeChangedFilter = new IntentFilter(Intent.ACTION_LOCALE_CHANGED);
getContext().registerReceiver(mLocaleChangeReceiver, localeChangedFilter);
publishBinderService(Context.NOTIFICATION_SERVICE, mService, /* allowIsolated= */ false,
DUMP_FLAG_PRIORITY_CRITICAL | DUMP_FLAG_PRIORITY_NORMAL);
publishLocalService(NotificationManagerInternal.class, mInternalService);
}
}
onStart方法會先調用init方法，然後注冊一些廣播來監聽一些常見的系統事件.
2、init方法如下所示：
public class NotificationManagerService extends SystemService {
private NotificationListeners mListeners;//主要用于管理通知的接收者.
void init(Looper looper, IPackageManager packageManager,
PackageManager packageManagerClient,
LightsManager lightsManager, NotificationListeners notificationListeners,
NotificationAssistants notificationAssistants, ConditionProviders conditionProviders,
ICompanionDeviceManager companionManager, SnoozeHelper snoozeHelper,
NotificationUsageStats usageStats, AtomicFile policyFile,
ActivityManager activityManager, GroupHelper groupHelper, IActivityManager am,
UsageStatsManagerInternal appUsageStats, DevicePolicyManagerInternal dpm) {
Resources resources = getContext().getResources();
mMaxPackageEnqueueRate = Settings.Global.getFloat(getContext().getContentResolver(),
Settings.Global.MAX_NOTIFICATION_ENQUEUE_RATE,
DEFAULT_MAX_NOTIFICATION_ENQUEUE_RATE);
mAccessibilityManager =
(AccessibilityManager) getContext().getSystemService(Context.ACCESSIBILITY_SERVICE);
mAm = am;
mPackageManager = packageManager;
mPackageManagerClient = packageManagerClient;
mAppOps = (AppOpsManager) getContext().getSystemService(Context.APP_OPS_SERVICE);
mVibrator = (Vibrator) getContext().getSystemService(Context.VIBRATOR_SERVICE);
mAppUsageStats = appUsageStats;
mAlarmManager = (AlarmManager) getContext().getSystemService(Context.ALARM_SERVICE);
mCompanionManager = companionManager;
mActivityManager = activityManager;
mDeviceIdleController = IDeviceIdleController.Stub.asInterface(
ServiceManager.getService(Context.DEVICE_IDLE_CONTROLLER));
mDpm = dpm;
//建立運作在system_server程序中的WorkerHandler
mHandler = new WorkerHandler(looper);
mRankingThread.start();
String[] extractorNames;
try {
extractorNames = resources.getStringArray(R.array.config_notificationSignalExtractors);
} catch (Resources.NotFoundException e) {
extractorNames = new String[0];
}
mUsageStats = usageStats;
mMetricsLogger = new MetricsLogger();
mRankingHandler = new RankingHandlerWorker(mRankingThread.getLooper());
mConditionProviders = conditionProviders;
mZenModeHelper = new ZenModeHelper(getContext(), mHandler.getLooper(), mConditionProviders);
mZenModeHelper.addCallback(new ZenModeHelper.Callback() {
@Override
public void onConfigChanged() {
savePolicyFile();
}
@Override
void onZenModeChanged() {
sendRegisteredOnlyBroadcast(NotificationManager.ACTION_INTERRUPTION_FILTER_CHANGED);
getContext().sendBroadcastAsUser(
new Intent(NotificationManager.ACTION_INTERRUPTION_FILTER_CHANGED_INTERNAL)
.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY_BEFORE_BOOT),
UserHandle.ALL, android.Manifest.permission.MANAGE_NOTIFICATIONS);
synchronized (mNotificationLock) {
updateInterruptionFilterLocked();
}
mRankingHandler.requestSort();
}
@Override
void onPolicyChanged() {
sendRegisteredOnlyBroadcast(NotificationManager.ACTION_NOTIFICATION_POLICY_CHANGED);
mRankingHandler.requestSort();
}
});
mRankingHelper = new RankingHelper(getContext(),
mPackageManagerClient,
mRankingHandler,
mZenModeHelper,
mUsageStats,
extractorNames);
mSnoozeHelper = snoozeHelper;
mGroupHelper = groupHelper;
// This is a ManagedServices object that keeps track of the listeners.
mListeners = notificationListeners;
// This is a MangedServices object that keeps track of the assistant.
mAssistants = notificationAssistants;
// Needs to be set before loadPolicyFile
mAllowedManagedServicePackages = this::canUseManagedServices;
mPolicyFile = policyFile;
loadPolicyFile();
mStatusBar = getLocalService(StatusBarManagerInternal.class);
if (mStatusBar != null) {
mStatusBar.setNotificationDelegate(mNotificationDelegate);
}
mNotificationLight = lightsManager.getLight(LightsManager.LIGHT_ID_NOTIFICATIONS);
mAttentionLight = lightsManager.getLight(LightsManager.LIGHT_ID_ATTENTION);
mFallbackVibrationPattern = getLongArray(resources,
R.array.config_notificationFallbackVibePattern,
VIBRATE_PATTERN_MAXLEN,
DEFAULT_VIBRATE_PATTERN);
mInCallNotificationUri = Uri.parse("file://" +
resources.getString(R.string.config_inCallNotificationSound));
mInCallNotificationAudioAttributes = new AudioAttributes.Builder()
.setContentType(AudioAttributes.CONTENT_TYPE_SONIFICATION)
.setUsage(AudioAttributes.USAGE_VOICE_COMMUNICATION)
.build();
mInCallNotificationVolume = resources.getFloat(R.dimen.config_inCallNotificationVolume);
mUseAttentionLight = resources.getBoolean(R.bool.config_useAttentionLight);
// Don't start allowing notifications until the setup wizard has run once.
// After that, including subsequent boots, init with notifications turned on.
// This works on the first boot because the setup wizard will toggle this
// flag at least once and we'll go back to 0 after that.
if (0 == Settings.Global.getInt(getContext().getContentResolver(),
Settings.Global.DEVICE_PROVISIONED, 0)) {
mDisableNotificationEffects = true;
}
mZenModeHelper.initZenMode();
mInterruptionFilter = mZenModeHelper.getZenModeListenerInterruptionFilter();
mUserProfiles.updateCache(getContext());
listenForCallState();
mSettingsObserver = new SettingsObserver(mHandler);
mArchive = new Archive(resources.getInteger(
R.integer.config_notificationServiceArchiveSize));
mIsTelevision = mPackageManagerClient.hasSystemFeature(FEATURE_LEANBACK)
|| mPackageManagerClient.hasSystemFeature(FEATURE_TELEVISION);
}
}
init方法中類型為NotificationListeners的變量mListeners比較重要，用于管理通知的接收者。
二、總結
關于NotificationManagerService的啟動流程，我們就簡單介紹這麼多，接下來我們将會具體分析一下SystemUI元件系統狀态欄StatusBar是如何監聽系統服務接受各種通知事件的。
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