notification的适配

1.1:Notification如果没有设置channelId,通知不会弹出，在logcat的error级别显示NotificationService提示日志：No Channel found for pkg=aaa, channelId=null,...notification=Notification(channel=null ...)

1.2:可见在安卓8.0及以上通知是必须配置ChannelId的。有两种方式给Notification对象添加channelId:

• 1.2.1:Notification notify = new NotificationCompat.Builder(this, channelId)...
• 1.2.2:NotificationCompat.Builder build.setChannelId(channelId)...

1.3:NotificationChannel的创建与注册

• public NotificationChannel(String id, CharSequence name, @Importance int importance)
• id 即 channelId
• name显示在通知管理里的标题
• importance代表此通道的重要性，从高到低限定了5个等级范围，有不同的表现行为

在NotificationManager#notify()前需要确保channelId已经被创建过: NotificationManager#createNotificationChannel(NotificationChannel);

2.1: 在实际开发中发现：即使按照官方规范添加了NotificationChannel,好多手机上依然无法弹出通知。追踪logcat发现有这么一句：

E/NotificationService: Suppressing notification from package by user request.

用户请求抑制此通知？追查源码NotificationManager#notify(int id, Notification notification) 最终调用了NotificationManagerService#enqueueNotificationInternal(......)

void enqueueNotificationInternal(final String pkg, final String opPkg, final int callingUid,final int callingPid, final String tag, final int id, final Notification notification,int incomingUserId) {
 ...
 if (!checkDisqualifyingFeatures(userId, notificationUid, id, tag, r)) {return;}
 ...
 mHandler.post(new EnqueueNotificationRunnable(userId, r));
}
private boolean checkDisqualifyingFeatures(int userId, int callingUid, int id, String tag,NotificationRecord r) {
  ...// blocked apps
  if (isBlocked(r, mUsageStats)) {return false;}
  return true;
}
protected boolean isBlocked(NotificationRecord r, NotificationUsageStats usageStats) {
  final String pkg = r.sbn.getPackageName();
  final int callingUid = r.sbn.getUid();
  final boolean isPackageSuspended = isPackageSuspendedForUser(pkg, callingUid);
  if (isPackageSuspended) {
      Slog.e(TAG, "Suppressing notification from package due to package suspended by administrator.");
      usageStats.registerSuspendedByAdmin(r);
      return isPackageSuspended;
  }
  
  final boolean isBlocked = mRankingHelper.getImportance(pkg, callingUid) == NotificationManager.IMPORTANCE_NONE
              || r.getChannel().getImportance() == NotificationManager.IMPORTANCE_NONE;
  if (isBlocked) {
      Slog.e(TAG, "Suppressing notification from package by user request.");
      usageStats.registerBlocked(r);
  }
  return isBlocked;
}

最终的isBlocked判断条件满足，导致notify操作被中断return。目前为止：通知权限在华为EMUI/魅族flyme/原生系统上默认是打开的，MIUI/VIVO/OPPO是默认关闭的，好吧为了通知能够正常使用先上一段权限工具代码试试：

boolean enabled = NotificationManagerCompat.from(context).areNotificationsEnabled();
if (enabled) {
    notificationManager.notify(notifyId, notification);
} else {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
        startActivity(new Intent(Settings.ACTION_APP_NOTIFICATION_SETTINGS)
                .putExtra(Settings.EXTRA_APP_PACKAGE, getPackageName()));
    } else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.GINGERBREAD) {
        Intent intent = new Intent(Settings.ACTION_APPLICATION_DETAILS_SETTINGS);
        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        intent.setData(Uri.fromParts("package",getPackageName(),null));
        startActivity(intent);
    } else {
        Intent intent = new Intent(Intent.ACTION_VIEW);
        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        intent.setClassName("com.android.settings","com.android.settings.InstalledAppDetails");
        intent.putExtra("com.android.settings.ApplicationPkgName", getPackageName());
        startActivity(intent);
    }
}

2.2: 事情还没结束：在oppo手机上发现即使引导用户打开了通知开关但是单个channel默认还是关闭的，需要两个开关都开启才能正常使用。而其他手机在开启通知时自动开启channelId的通知开关。

再改改：

Build.VERSION_CODES.O           =>  26
Build.VERSION_CODES.LOLLIPOP    =>  21
Build.VERSION_CODES.GINGERBREAD =>  9
NotificationChannel channelUsed = manager.getNotificationChannel(notification.getChannelId());
boolean isNotifyEnable = NotificationManagerCompat.from(this).areNotificationsEnabled();
boolean isChannelEnable = true;
if (Build.VERSION.SDK_INT >= 26) {
    isChannelEnable = channelUsed.getImportance() != NotificationManager.IMPORTANCE_NONE;
}
if (isNotifyEnable && isChannelEnable) {
    manager.notify(notifyId, notification);
} else if (!isNotifyEnable) {
    if (Build.VERSION.SDK_INT >= 26) {
        startActivity(new Intent(Settings.ACTION_APP_NOTIFICATION_SETTINGS)
                  .putExtra(Settings.EXTRA_APP_PACKAGE, getPackageName()));
    }else if (Build.VERSION.SDK_INT >= 21) {
        startActivity(new Intent("android.settings.APP_NOTIFICATION_SETTINGS")
                  .putExtra("android.provider.extra.APP_PACKAGE", getPackageName()));
    } else if (Build.VERSION.SDK_INT >= 9) {
        Intent intent = new Intent(Settings.ACTION_APPLICATION_DETAILS_SETTINGS);
        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        intent.setData(Uri.fromParts("package", getPackageName(), null));
        startActivity(intent);
    } else {
        Intent intent = new Intent(Intent.ACTION_VIEW);
        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        intent.setClassName("com.android.settings", "com.android.settings.InstalledAppDetails");
        intent.putExtra("com.android.settings.ApplicationPkgName", getPackageName());
        startActivity(intent);
    }
}else{
   用户打开了通知开关，但是没有允许当前channel的通知，根据通知重要性自行决定如何提示用户
}

• 注意点1：查看安卓5.0(api21)与8.0(api26)的源码可知Settings. ACTION_APP_NOTIFICATION_SETTINGS 的值其实就是 "android.settings. APP_NOTIFICATION_SETTINGS",只是在安卓8.0以下这个常量对开发者是隐藏的。因此上述代码如想简化可省略if(Build.VERSION.SDK_INT >= 26){...}这一块。
• 注意点2：NotificationChannel channelUsed 在构建通知的时候使用的NotificationChannel和真实使用的NotificationChannel可能是不同的。因为createNotificationChannels在service层实现的时候保存了一个record缓存，notify的时候是从record取的channel对象，此时importance的值极可能已经产生了变化。因此需要使用manager.getNotificationChannel(notification.getChannelId())返回的NotificationChannel对象
• 小插曲：测试时发现vivo X21有两个通知管理页面：
  明显右边很漂酿啊有木有 vivo的设计很符合我的审美哈哈，试试改下跳转，左边的太丑了不要了。通过shell 命令dumpsys activity | grep -i run找到落地页：com.android.systemui / com.vivo.systemui.statusbar.notification.settings.channels.NotificationSettingsActivity 先不管参数跑下试试，不出所料崩了，提示Permission Denial: starting Intent{...}not exported from uid 10023。activity没有设置exported属性为true，无法访问。暂时想不到怎么暴力破解...

boolean isNotifyEnable = NotificationManagerCompat.from(this).areNotificationsEnabled();
if(isNotifyEnable){
    manager.notify(notifyId,notification);
}else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
    startActivity(new Intent("android.settings.APP_NOTIFICATION_SETTINGS")
          .putExtra("android.provider.extra.APP_PACKAGE", getPackageName()));
} else/* if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.GINGERBREAD) */{
    Intent intent = new Intent(Settings.ACTION_APPLICATION_DETAILS_SETTINGS);
    intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
    intent.setData(Uri.fromParts("package", getPackageName(), null));
    startActivity(intent);
}   考虑到目前app没人再适配android 2.x,因此最后一个else省略