Android 8.0 通知栏适配

8.0新增了一个NotificationChannel这个特性，在target >=26的情况下，会发现无法展示通知。

解决方案

public void showNotification(){
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            String channelId = "chat";
            String channelName = "chat message";
            int importance = NotificationManager.IMPORTANCE_HIGH;
            createNotificationChannel(channelId, channelName, importance);
          }

     Notification notification = new NotificationCompat.Builder(this, "chat")
                .setContentTitle(title)
                .setContentText(body)
                .setCategory(NotificationCompat.CATEGORY_MESSAGE)
                .setFullScreenIntent(null, true)
                .setContentIntent(pendingIntentClick)
                .setWhen(System.currentTimeMillis())
                .setVisibility(Notification.VISIBILITY_PUBLIC)
                .setSmallIcon(R.drawable.ic_launcher)
                .setLargeIcon(BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher))
                .setAutoCancel(true)
                .build();
    }

    @RequiresApi(api = Build.VERSION_CODES.O)
    private void createNotificationChannel(String channelId, String channelName, int importance) {
        NotificationChannel channel = new NotificationChannel(channelId, channelName, importance);
        NotificationManager manager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
        manager.createNotificationChannel(channel);
    }