In this tutorial, you'll learn how to create a User Interface (UI) in this case, will be an hp bar. We'll do a quick walkthrough of the process step by step, covering the basics of using the CustomUI class and performing simple calculations in Lua. By the end of this guide, you'll be able to implement a functional and visually appealing HP bar in your game.

• Using the CustomUI Class: Understand how use the CustomUI class to create dynamic UI elements.
• Basic Lua Calculations: Learn how to perform basic calculations such as the ones necessary for scaling the HP bar based on the player's current and maximum health.

Before continuing with the tutorial, let's see the result first.

• Background: This is a picture component that serves as the backdrop for the HP bar. It lies underneath the HP bar itself.
• HP Bar: Another picture component that represents the actual HP bar, which will visually decrease as the player loses health.
• Text Display: A word component that displays the current HP and maximum HP values. This helps players understand their exact health status at a glance.

You can see the order of the components in the image below.

After taking a look at the code. We will make a quick explanation of the code and its parts. Remember to replace the ids with the ones of your elements.

local CurUi = {
 
    Id = [[7377127869834574121]],
 
    HpBarBg = [[7377127869834574121_1]],
    HpBar = [[7377127869834574121_2]],
    HpBarText = [[7377127869834574121_3]],
 
    HpBarWidth = 445,
    HpBarLength = 80
}
 
function UpdateHpUi(e) 
 
    local playerid = e['eventobjid']
    local playerattr = e['playerattr'] or 2
 
    if playerattr == PLAYERATTR.CUR_HP then 
 
        local _, PlayerHp = Player:getAttr(playerid, PLAYERATTR.CUR_HP)
        local _, PlayerMaxHp = Player:getAttr(playerid, PLAYERATTR.MAX_HP)
 
        local ScaleRatio = (CurUi.HpBarWidth / PlayerMaxHp) * PlayerHp
 
        if PlayerMaxHp <= 0 then PlayerMaxHp = 0 end
 
        Customui:setText(playerid, CurUi.Id, CurUi.HpBarText, math.floor(PlayerHp) .. "/" .. PlayerMaxHp)
        Customui:setSize(playerid, CurUi.Id, CurUi.HpBar, ScaleRatio, CurUi.HpBarLength)
 
    end
 
end
 
ScriptSupportEvent:registerEvent([=[Game.AnyPlayer.EnterGame]=], UpdateHpUi)
ScriptSupportEvent:registerEvent([=[Player.ChangeAttr]=], UpdateHpUi)

After that, we will explain.

The code begins by defining a table named CurUi which stores various the id of all the elements in the HP bar, it stores:

• Id: The id of the UI component.
• HpBarBg: Id of the HP bar background.
• HpBar: Id for the actual HP bar that changes size based on the player's health.
• HpBarText: Id for the text component displaying the current and maximum HP.
• HpBarWidth: The maximum width of the HP bar.
• HpBarLength: The height (length) of the HP bar.

Next, a function named UpdateHpUi is defined. This function will update the HP bar whenever the player's health changes.

• Parameters: The function takes a parameter e, which contains event information. This includes details like the player's ID and the type of event.
• Check Player Attribute: The function checks if the event is related to the player's current health (HP) using if playerattr == PLAYERATTR.CUR_HP then it gets the:

• Current HP: Retrieves the player's current health using Player:getAttr(playerid, PLAYERATTR.CUR_HP).
• Maximum HP: Retrieves the player's maximum health using Player:getAttr(playerid, PLAYERATTR.MAX_HP).

Then it calculates the scale that the HP bar must have with the operation

(HpBarWidth / PlayerMaxHp) * PlayerHp

Update HP Text: Sets the text of the HP bar to display the current and maximum HP using Customui:setText(playerid, CurUi.Id, CurUi.HpBarText, math.floor(PlayerHp) .. “/” .. PlayerMaxHp). Update HP Bar Size: Adjusts the size of the HP bar to reflect the player's current health using Customui:setSize(playerid, CurUi.Id, CurUi.HpBar, ScaleRatio, CurUi.HpBarLength). Registering Events

Finally, the script registers the UpdateHpUi function to be called when any player enters the game, or when a player attribute changes, like in this case, the player's health.