I hope the below code will help you most to understand which properties ate most important to display heads-up notifications and also by using this code I didn't find the issue of not working sometimes.
@Override
public void onMessageReceived(RemoteMessage remoteMessage) {
sendNotification(remoteMessage.getNotification().getTitle(),
remoteMessage.getNotification().getBody(),remoteMessage.getData());
}
private void sendNotification(String messageTitle, String messageBody,
Map<String, String> data) {
Intent intent = HomeActivity.getHomeActivityIntent(this,data.get(Constants.PUSH_URL));
PendingIntent pendingIntent = PendingIntent.getActivity(this, 0 /* Request code */, intent,
PendingIntent.FLAG_ONE_SHOT);
NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(this, "1")
.setSmallIcon(R.drawable.icon_notification)
.setContentTitle(messageTitle)
.setContentText(messageBody)
.setContentIntent(pendingIntent)
.setDefaults(DEFAULT_SOUND | DEFAULT_VIBRATE) //Important for heads-up notification
.setPriority(Notification.PRIORITY_MAX); //Important for heads-up notification
Notification buildNotification = mBuilder.build();
int notifyId = (int) System.currentTimeMillis(); //For each push the older one will not be replaced for this unique id
// Since android Oreo notification channel is needed.
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
String name = getString(R.string.channel_name);
String description = getString(R.string.channel_description);
int importance = NotificationManager.IMPORTANCE_HIGH; //Important for heads-up notification
NotificationChannel channel = new NotificationChannel(getResources().getString(R.string.default_notification_channel_id),
name,
importance);
channel.setDescription(description);
channel.setShowBadge(true);
channel.setLockscreenVisibility(Notification.VISIBILITY_PUBLIC);
NotificationManager notificationManager = getSystemService(NotificationManager.class);
if (notificationManager != null) {
notificationManager.createNotificationChannel(channel);
notificationManager.notify(notifyId, buildNotification);
}
}else{
NotificationManager mNotifyMgr = (NotificationManager)getSystemService(NOTIFICATION_SERVICE);
if (mNotifyMgr != null) {
mNotifyMgr.notify(notifyId, buildNotification);
}
}
}
To display heads-up, copy and paste the whole code and also fix errors based on strings and imports. After getting successful heads-up, remove or add anything as your requirement.
You may also follow my post on medium at this link for more detail answer.