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Android O---适配NotificationChannel

继之前跪在Android N的StrictMode上了。现在又跪在的Android O 的NotificationChannel上了

场景如下:

某些场景中需要上传图片,选择图片或者拍照时使用系统的图库会将自己的app置于后台,若选择图片的时间过长,则可能会导致自己的app会杀死。看了一下传承下来的代码,是在这种情况下发送一个前台通知startForeground,使此服务在前台运行。但是会在通知栏上显示一个应用正在运行的通知

通知

源码分析

查看Android 28的源码,发现调用链如下:

首先 Service.java中调用

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public final void startForeground(int id, Notification notification) {
try {
mActivityManager.setServiceForeground(
new ComponentName(this, mClassName), mToken, id,
notification, 0);
} catch (RemoteException ex) {
}
}

这里的mActivityManager的声明是private IActivityManager mActivityManager = null;在这里,IActivityManager的实现类是ActivityManagerService

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@Override
public void setServiceForeground(ComponentName className, IBinder token,
int id, Notification notification, int flags) {
synchronized(this) {
mServices.setServiceForegroundLocked(className, token, id, notification, flags);
}
}
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public void setServiceForegroundLocked(ComponentName className, IBinder token,
int id, Notification notification, int flags) {
final int userId = UserHandle.getCallingUserId();
final long origId = Binder.clearCallingIdentity();
try {
ServiceRecord r = findServiceLocked(className, token, userId);
if (r != null) {
setServiceForegroundInnerLocked(r, id, notification, flags);
}
} finally {
Binder.restoreCallingIdentity(origId);
}
}

finally中调用的Binder方法是一个native方法,主要看一下setServiceForegroundInnerLocked:

方法太长,关注一下我们需要的

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// Apps under strict background restrictions simply don't get to have foreground
// services, so now that we've enforced the startForegroundService() contract
// we only do the machinery of making the service foreground when the app
// is not restricted.
if (!ignoreForeground) {
if (r.foregroundId != id) {
cancelForegroundNotificationLocked(r);
r.foregroundId = id;
}
notification.flags |= Notification.FLAG_FOREGROUND_SERVICE;
r.foregroundNoti = notification;
if (!r.isForeground) {
final ServiceMap smap = getServiceMapLocked(r.userId);
if (smap != null) {
ActiveForegroundApp active = smap.mActiveForegroundApps.get(r.packageName);
if (active == null) {
active = new ActiveForegroundApp();
active.mPackageName = r.packageName;
active.mUid = r.appInfo.uid;
active.mShownWhileScreenOn = mScreenOn;
if (r.app != null) {
active.mAppOnTop = active.mShownWhileTop =
r.app.uidRecord.curProcState
<= ActivityManager.PROCESS_STATE_TOP;
}
active.mStartTime = active.mStartVisibleTime
= SystemClock.elapsedRealtime();
smap.mActiveForegroundApps.put(r.packageName, active);
requestUpdateActiveForegroundAppsLocked(smap, 0);
}
active.mNumActive++;
}
r.isForeground = true;
mAm.mAppOpsService.startOperation(
AppOpsManager.getToken(mAm.mAppOpsService),
AppOpsManager.OP_START_FOREGROUND, r.appInfo.uid, r.packageName,
true);
StatsLog.write(StatsLog.FOREGROUND_SERVICE_STATE_CHANGED,
r.appInfo.uid, r.shortName,
StatsLog.FOREGROUND_SERVICE_STATE_CHANGED__STATE__ENTER);
}
r.postNotification();
if (r.app != null) {
updateServiceForegroundLocked(r.app, true);
}
getServiceMapLocked(r.userId).ensureNotStartingBackgroundLocked(r);
mAm.notifyPackageUse(r.serviceInfo.packageName,
PackageManager.NOTIFY_PACKAGE_USE_FOREGROUND_SERVICE);
}

这里面的r.postNotification();这里的rServiceRecord的一个实例对象,在该方法中调用了ams.mHandler.post(new Runnable())方法,ams是ActivityManagerService的一个实例,在这里创建了一个匿名内部类:

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ams.mHandler.post(new Runnable() {
public void run() {
NotificationManagerInternal nm = LocalServices.getService(
NotificationManagerInternal.class);
if (nm == null) {
return;
}
Notification localForegroundNoti = _foregroundNoti;
try {
if (localForegroundNoti.getSmallIcon() == null) {
// It is not correct for the caller to not supply a notification
// icon, but this used to be able to slip through, so for
// those dirty apps we will create a notification clearly
// blaming the app.
Slog.v(TAG, "Attempted to start a foreground service ("
+ name
+ ") with a broken notification (no icon: "
+ localForegroundNoti
+ ")");

CharSequence appName = appInfo.loadLabel(
ams.mContext.getPackageManager());
if (appName == null) {
appName = appInfo.packageName;
}
Context ctx = null;
try {
ctx = ams.mContext.createPackageContextAsUser(
appInfo.packageName, 0, new UserHandle(userId));

Notification.Builder notiBuilder = new Notification.Builder(ctx,
localForegroundNoti.getChannelId());

// it's ugly, but it clearly identifies the app
notiBuilder.setSmallIcon(appInfo.icon);

// mark as foreground
notiBuilder.setFlag(Notification.FLAG_FOREGROUND_SERVICE, true);

Intent runningIntent = new Intent(
Settings.ACTION_APPLICATION_DETAILS_SETTINGS);
runningIntent.setData(Uri.fromParts("package",
appInfo.packageName, null));
PendingIntent pi = PendingIntent.getActivityAsUser(ams.mContext, 0,
runningIntent, PendingIntent.FLAG_UPDATE_CURRENT, null,
UserHandle.of(userId));
notiBuilder.setColor(ams.mContext.getColor(
com.android.internal
.R.color.system_notification_accent_color));
notiBuilder.setContentTitle(
ams.mContext.getString(
com.android.internal.R.string
.app_running_notification_title,
appName));
notiBuilder.setContentText(
ams.mContext.getString(
com.android.internal.R.string
.app_running_notification_text,
appName));
notiBuilder.setContentIntent(pi);

localForegroundNoti = notiBuilder.build();
} catch (PackageManager.NameNotFoundException e) {
}
}
if (nm.getNotificationChannel(localPackageName, appUid,
localForegroundNoti.getChannelId()) == null) {
int targetSdkVersion = Build.VERSION_CODES.O_MR1;
try {
final ApplicationInfo applicationInfo =
ams.mContext.getPackageManager().getApplicationInfoAsUser(
appInfo.packageName, 0, userId);
targetSdkVersion = applicationInfo.targetSdkVersion;
} catch (PackageManager.NameNotFoundException e) {
}
if (targetSdkVersion >= Build.VERSION_CODES.O_MR1) {
throw new RuntimeException(
"invalid channel for service notification: "
+ foregroundNoti);
}
}
if (localForegroundNoti.getSmallIcon() == null) {
// Notifications whose icon is 0 are defined to not show
// a notification, silently ignoring it. We don't want to
// just ignore it, we want to prevent the service from
// being foreground.
throw new RuntimeException("invalid service notification: "
+ foregroundNoti);
}
nm.enqueueNotification(localPackageName, localPackageName,
appUid, appPid, null, localForegroundId, localForegroundNoti,userId);

foregroundNoti = localForegroundNoti; // save it for amending next time
} catch (RuntimeException e) {
Slog.w(TAG, "Error showing notification for service", e);
// If it gave us a garbage notification, it doesn't
// get to be foreground.
ams.setServiceForeground(name, ServiceRecord.this,
0, null, 0);
ams.crashApplication(appUid, appPid, localPackageName, -1,
"Bad notification for startForeground: " + e);
}
}
});

首先检查一下getSmallIcon是不是空,如果是空的,打印日志,然后创建一个新的Notification。然后走不为空的判断:检查有没有NotificationChannel:

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nm.getNotificationChannel(localPackageName, appUid,localForegroundNoti.getChannelId()) == null

这里面如果targetSdkVersion >= Build.VERSION_CODES.O_MR1,则会抛出invalid channel for service notification异常。

如果一切正常,入队列发通知。


至此,应用中发生崩溃的原因找到了,targetSdk是28,又没有NotificationChannel。

那么,NotificationChannel又是个卵????

NotificationChannel

从Android 8.0系统开始,Google引入了通知渠道这个概念。

什么是通知渠道呢?顾名思义,就是每条通知都要属于一个对应的渠道。每个App都可以自由地创建当前App拥有哪些通知渠道,但是这些通知渠道的控制权都是掌握在用户手上的。用户可以自由地选择这些通知渠道的重要程度,是否响铃、是否振动、或者是否要关闭这个渠道的通知。

Google这次对于8.0系统通知渠道的推广态度还是比较强硬的。

首先,如果你升级了appcompat库,那么所有使用appcompat库来构建通知的地方全部都会进行废弃方法提示,如下所示:

通知

创建NotificationChannel

创建NotificationChannel对象(不必每次创建),并且创建通知渠道的代码只在第一次执行的时候才会创建,以后每次执行创建代码系统会检测到该通知渠道已经存在了,因此不会重复创建,也并不会影响任何效率。

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if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
String channelId = "take_photo";
String channelName = "拍照选择图片";
int importance = NotificationManager.IMPORTANCE_HIGH;
NotificationManager
notificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
NotificationChannel channel = notificationManager.getNotificationChannel(channelId);
if (channel == null) {
channel = new NotificationChannel(channelId, channelName, importance);
}
notificationManager.createNotificationChannel(channel);
if (channel.getImportance() == NotificationManager.IMPORTANCE_NONE) {
Intent intent = new Intent(Settings.ACTION_CHANNEL_NOTIFICATION_SETTINGS);
intent.putExtra(Settings.EXTRA_APP_PACKAGE, getPackageName());
intent.putExtra(Settings.EXTRA_CHANNEL_ID, channel.getId());
startActivity(intent);
Toast.makeText(this, "请手动将通知打开", Toast.LENGTH_SHORT).show();
} else {
Notification nf = new Notification.Builder(this, channelId)
.setContentText("setContentText")
.setSettingsText("setSettingsText")
.setContentTitle("setContentTitle")
.setSmallIcon(R.drawable.ic_launcher_background)
.build();
notificationManager.notify(1, nf);
}
}
}

首先要确保的是当前手机的系统版本必须是Android 8.0系统或者更高,因为低版本的手机系统并没有通知渠道这个功能,不做系统版本检查的话会在低版本手机上造成崩溃。创建一个通知渠道至少需要渠道ID、渠道名称以及重要等级这三个参数,其中渠道ID可以随便定义,只要保证全局唯一性就可以。渠道名称是给用户看的,需要能够表达清楚这个渠道的用途。重要等级的不同则会决定通知的不同行为,当然这里只是初始状态下的重要等级,用户可以随时手动更改某个渠道的重要等级,App是无法干预的。

创建通知的代码就不再多做解释了,和传统创建通知的方法没什么两样,只是在NotificationCompat.Builder中需要多传入一个通知渠道ID,那么这里我们传入刚刚创建的渠道ID。

管理通知渠道

通知渠道一旦创建之后就不能再通过代码修改了,如果用户不小心关闭了该渠道,我们可以通知用户手动去修改,就像动态权限申请一样:

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if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
NotificationChannel channel = manager.getNotificationChannel("chat");
if (channel.getImportance() == NotificationManager.IMPORTANCE_NONE) {
Intent intent = new Intent(Settings.ACTION_CHANNEL_NOTIFICATION_SETTINGS);
intent.putExtra(Settings.EXTRA_APP_PACKAGE, getPackageName());
intent.putExtra(Settings.EXTRA_CHANNEL_ID, channel.getId());
startActivity(intent);
Toast.makeText(this, "请手动将通知打开", Toast.LENGTH_SHORT).show();
}
}

通过getNotificationChannel()方法获取到了NotificationChannel对象,然后就可以读取该通知渠道下的所有配置了。这里我们判断如果通知渠道的importance等于IMPORTANCE_NONE,就说明用户将该渠道的通知给关闭了,这时会跳转到通知的设置界面提醒用户手动打开。

Android 8.0还赋予了我们删除通知渠道的功能,只需使用如下代码即可删除:

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NotificationManager manager = (NotificationManager)getSystemService(NOTIFICATION_SERVICE);
manager.deleteNotificationChannel(channelId);

NotificationChannel章节参考 https://mp.weixin.qq.com/s/PG8XxHEHpijL4AMZ4AGP8g


以上