Part of my PlayerExpChangeEvent is being overridden by vanilla - plugins

Question

I'm making a spigot plugin (version 1.8.8) that has an function that I know works because it fires flawlessly through my command. However, when I call it at the end of a PlayerExpChangeEvent, it seems like vanilla leveling overrides the bar, making it go up way more that it is supposed to. Running the command/function after this happens makes the bar go back to how it is supposed to be. I've tried setting my event's priority to highest (and when that didn't work, to lowest) but no matter what my function appears to be completely ignored when called inside the event.
Here is some code:
#EventHandler(priority=EventPriority.HIGHEST)
public void onXpGain(PlayerExpChangeEvent event)
{
// Load custom levels from config
ArrayList<String> levelList = new ArrayList<String>(plugin.getConfig().getStringList("levels"));
if (!((String)levelList.get(0)).equals("none"))
{
Player player = event.getPlayer();
Iterator<String> var4 = levelList.iterator();
while (var4.hasNext())
{
String s = (String)var4.next();
String[] splits = s.split(" ");
int levelCompare = Integer.parseInt(splits[0]);
int playerLvl = player.getLevel();
// Detect if on correct tier, else continue iteration
if (playerLvl == levelCompare - 1)
{
// Calculate the player's new XP amount
int totalXp = player.getTotalExperience() + event.getAmount();
player.setTotalExperience(totalXp);
updateBar(event.getPlayer()); // <-- THIS IS THE FUNCTION
return;
}
}
// At max level
player.setTotalExperience(player.getTotalExperience() + event.getAmount());
player.setLevel(getHighestLevel(levelList));
player.setExp(1.0f);
}
}
And here is the function itself. Keep in mind that it works fine when called through a command and not an event. It's purpose is to use the player's total XP to set the level and bar. Neither set correctly in the event; it instead embraces vanilla leveling.
public static void updateBar(Player player) {
ArrayList<String> levelList = new ArrayList<String>(plugin.getConfig().getStringList("levels"));
int totalXp = player.getTotalExperience();
player.setLevel(getHighestLevelForXp(totalXp, levelList));
if (player.getLevel() < getHighestLevel(levelList)) {
int lvlDiff = getTotalXpToLevel(player.getLevel() + 1,levelList) - getTotalXpToLevel(player.getLevel(),levelList);
int xpDiff = totalXp - getTotalXpToLevel(player.getLevel(),levelList);
player.setExp((float)xpDiff/lvlDiff);
} else {
player.setLevel(getHighestLevel(levelList));
player.setExp(0.0f);
}
return;
}
The command where the function works correctly is a bare-bones call to the function and doesn't need a mention here. Does anyone know how to get my event to override vanilla xp gain? The update works through the command, just not natural xp gain. It is already confirmed that the event DOES fire, as the rest of the event changes the internal xp amount, but the visual effects are overridden by vanilla. Can anyone help? Thanks.

Answer 1

Only setting the Player's EXP won't be enough for your desired behaviour. The Vanilla behaviour will still complete, as you're not changing how the event will add EXP to the player.
Currently, your event is working like this:
And PlayerExpGainEvent isn't cancellable, so you cannot undo it's addition of EXP.
What you can do instead is to set the EXP the event will add to 0, therefore not changing the player's EXP after your interception.
event.setAmount(0); //Cancelling the EXP addition
I would recommend to set your event to a high priority, so that other events that depend on Experience gain won't trigger when you set the amount gained to 0.