无法在通道“ null”上发布通知，目标Api为26

Question

显示两个日志

1：不建议将流类型用于除音量控制之外的其他操作

2：有关如何将android.media.AudioAttributes用于限定播放用例的信息，请参见setSound（）的文档

Answer 1

从developer documentation：

当您以Android 8.0（API级别26）为目标时，必须实现一个或多个通知通道才能向用户显示通知。

int NOTIFICATION_ID = 234;
NotificationManager notificationManager = (NotificationManager) ctx.getSystemService(Context.NOTIFICATION_SERVICE);

if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
    String CHANNEL_ID = "my_channel_01";
    CharSequence name = "my_channel";
    String Description = "This is my channel";
    int importance = NotificationManager.IMPORTANCE_HIGH;
    NotificationChannel mChannel = new NotificationChannel(CHANNEL_ID, name, importance);
    mChannel.setDescription(Description);
    mChannel.enableLights(true);
    mChannel.setLightColor(Color.RED);
    mChannel.enableVibration(true);
    mChannel.setVibrationPattern(new long[]{100, 200, 300, 400, 500, 400, 300, 200, 400});
    mChannel.setShowBadge(false);
    notificationManager.createNotificationChannel(mChannel);
}

NotificationCompat.Builder builder = new NotificationCompat.Builder(ctx, CHANNEL_ID)
    .setSmallIcon(R.mipmap.ic_launcher)
    .setContentTitle(title)
    .setContentText(message);

Intent resultIntent = new Intent(ctx, MainActivity.class);
TaskStackBuilder stackBuilder = TaskStackBuilder.create(ctx);
stackBuilder.addParentStack(MainActivity.class);
stackBuilder.addNextIntent(resultIntent);
PendingIntent resultPendingIntent = stackBuilder.getPendingIntent(0, PendingIntent.FLAG_UPDATE_CURRENT);
builder.setContentIntent(resultPendingIntent);
notificationManager.notify(NOTIFICATION_ID, builder.build());

要注意的一件有趣的事情：如果已经存在一个通道，则调用createNotificationChannel无效，因此可以create all channels whenever you start your application。

Answer 2

如果您的最低API是Oreo，Gulzar Bhat的答案将非常有效。但是，如果最低要求较低，则必须将NotificationChannel代码包装在平台级别检查中。之后，您仍然可以使用id，在Oreo之前它将被忽略：

if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
    int importance = NotificationManager.IMPORTANCE_LOW;
    NotificationChannel notificationChannel = new NotificationChannel(NOTIFICATION_CHANNEL_ID, NOTIFICATION_CHANNEL_NAME, importance);
    notificationChannel.enableLights(true);
    notificationChannel.setLightColor(Color.RED);
    notificationChannel.enableVibration(true);
    notificationChannel.setVibrationPattern(new long[]{100, 200, 300, 400, 500, 400, 300, 200, 400});
    notificationManager.createNotificationChannel(notificationChannel);
}

NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(context, NOTIFICATION_CHANNEL_ID);

NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
notificationManager.notify((int)(System.currentTimeMillis()/1000), mBuilder.build());

Answer 3

您可以通过两种方式解决此问题，但是对于这两种方式，您都需要创建一个具有特定渠道ID的通知渠道。

NotificationManager mNotificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
String id = "my_channel_01";
int importance = NotificationManager.IMPORTANCE_LOW;
NotificationChannel mChannel = new NotificationChannel(id, name,importance);
mChannel.enableLights(true);
mNotificationManager.createNotificationChannel(mChannel);

第一种方法是在构造函数中设置通知通道：
Notification notification = new Notification.Builder(MainActivity.this , id).setContentTitle("Title");
mNotificationManager.notify("your_notification_id", notification);

第二种方法是通过Notificiation.Builder.setChannelId（）设置通道
Notification notification = new Notification.Builder(MainActivity.this).setContentTitle("Title").
setChannelId(id);
mNotificationManager.notify("your_notification_id", notification);

希望这会有所帮助

Answer 4

首先创建通知渠道：

public static final String NOTIFICATION_CHANNEL_ID = "4655";
//Notification Channel
        CharSequence channelName = NOTIFICATION_CHANNEL_NAME;
        int importance = NotificationManager.IMPORTANCE_LOW;
        NotificationChannel notificationChannel = new NotificationChannel(NOTIFICATION_CHANNEL_ID, NOTIFICATION_CHANNEL_NAME, importance);
        notificationChannel.enableLights(true);
        notificationChannel.setLightColor(Color.RED);
        notificationChannel.enableVibration(true);
        notificationChannel.setVibrationPattern(new long[]{100, 200, 300, 400, 500, 400, 300, 200, 400});


NotificationManager notificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
        notificationManager.createNotificationChannel(notificationChannel);

然后在构造函数中使用频道ID：
final NotificationCompat.Builder builder = new NotificationCompat.Builder(context, NOTIFICATION_CHANNEL_ID)
                .setDefaults(Notification.DEFAULT_ALL)
                .setSmallIcon(R.drawable.ic_timers)
                .setVibrate(new long[]{100, 200, 300, 400, 500, 400, 300, 200, 400})
                .setSound(null)
                .setContent(contentView)
                .setPriority(NotificationCompat.PRIORITY_DEFAULT)
                .setLargeIcon(picture)
                .setTicker(sTimer)
                .setContentIntent(timerListIntent)
                .setAutoCancel(false);

Answer 5

此问题与旧的FCM版本有关。

将您的依赖关系更新为com.google.firebase:firebase-messaging:15.0.2或更高。

这将纠正错误

failed to post notification on channel null

当您的应用在后台接收通知时，因为现在Firebase提供了具有基本设置的默认通知通道。
但是您也可以在清单中为FCM指定默认的通知通道。
<meta-data
android:name="com.google.firebase.messaging.default_notification_channel_id"
android:value="@string/default_notification_channel_id"/>

要了解更多here

Answer 6

我有一个类似的问题，但是将服务作为后台活动启动，该代码在服务中起作用：

public static final int PRIMARY_FOREGROUND_NOTIF_SERVICE_ID = 1001;

@Override
public void onCreate() {
    super.onCreate();

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {

        String id = "_channel_01";
        int importance = NotificationManager.IMPORTANCE_LOW;
        NotificationChannel mChannel = new NotificationChannel(id, "notification", importance);
        mChannel.enableLights(true);

        Notification notification = new Notification.Builder(getApplicationContext(), id)
                .setSmallIcon(R.drawable.ic_launcher)
                .setContentTitle("My chat")
                .setContentText("Listening for incoming messages")
                .build();

        NotificationManager mNotificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
        if (mNotificationManager != null) {
            mNotificationManager.createNotificationChannel(mChannel);
            mNotificationManager.notify(PRIMARY_FOREGROUND_NOTIF_SERVICE_ID, notification);
        }

        startForeground(PRIMARY_FOREGROUND_NOTIF_SERVICE_ID, notification);
    }
}

这不是最好的解决方案，而只是在后台启动服务确实起作用

Answer 7

如果出现此错误，请注意2个项目，它们会顺序排列：

NotificationChannel mChannel = new NotificationChannel(id, name, importance);
1. builder = new NotificationCompat.Builder(this, id);

也仅创建一次NotificationManager notifManager和NotificationChannel mChannel。

通知有必填项：

builder.setContentTitle() // required  
       .setSmallIcon()    // required 
       .setContentText()  // required  

请参见On Android 8.1 API 27 notification does not display中的示例。

Answer 8

String CHANNEL_ID = "my_channel";

NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this,CHANNEL_ID);