在Android Oreo中，FCM（Firebase Cloud Messaging）推送通知需要做一些额外的适配工作。以下是一个解决Android Oreo中FCM推送通知问题的示例代码：

1. 在AndroidManifest.xml文件中添加渠道声明：

2. 在res/values/strings.xml文件中定义默认通知渠道ID：

    default_channel

3. 创建一个NotificationHelper类来处理通知相关操作：

import android.app.NotificationChannel;
import android.app.NotificationManager;
import android.content.Context;
import android.os.Build;

public class NotificationHelper {
    private static final String CHANNEL_ID = "default_channel";
    private static final String CHANNEL_NAME = "Default Channel";
    private static final String CHANNEL_DESCRIPTION = "Default notification channel";

    public static void createNotificationChannel(Context context) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            NotificationManager notificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
            NotificationChannel channel = new NotificationChannel(CHANNEL_ID, CHANNEL_NAME, NotificationManager.IMPORTANCE_DEFAULT);
            channel.setDescription(CHANNEL_DESCRIPTION);
            notificationManager.createNotificationChannel(channel);
        }
    }
}

4. 在FirebaseMessagingService中调用NotificationHelper类的方法：

import com.google.firebase.messaging.FirebaseMessagingService;
import com.google.firebase.messaging.RemoteMessage;

public class MyFirebaseMessagingService extends FirebaseMessagingService {
    @Override
    public void onMessageReceived(RemoteMessage remoteMessage) {
        // 处理收到的消息
        showNotification(remoteMessage.getNotification().getTitle(), remoteMessage.getNotification().getBody());
    }

    private void showNotification(String title, String body) {
        NotificationHelper.createNotificationChannel(this);

        // 创建通知
        NotificationCompat.Builder builder = new NotificationCompat.Builder(this, NotificationHelper.CHANNEL_ID)
                .setContentTitle(title)
                .setContentText(body)
                .setSmallIcon(R.drawable.ic_notification)
                .setAutoCancel(true);

        NotificationManagerCompat notificationManager = NotificationManagerCompat.from(this);
        notificationManager.notify(0, builder.build());
    }
}

这样，在Android Oreo中，你就能够正确地显示FCM推送的通知了。请记得将代码中的图标和通知内容替换为你自己的内容。