Creating A Stamina Bar w/ New Unity Input system

5 min readJun 13, 2025

Objective: Learn how to build a stamina bar that depletes when holding the sprint key and recharges when the key is released.

· Add a UI Slider
· Registering Input
· Input Callbacks
· Coding the Stamina Bar
∘ Sprint Start
∘ Sprint Cancel
· Executing the Sprint Action and the Interactive Stamina Bar
· Bonus Code Tip on Courtines:
· The Result

Add a UI Slider

🎨 Want your slider to look like the one in the thumbnail? Here’s a quick style guide:

Start by adding a UI Slider to your scene.

Remove the handle

Change the Background color

Edit the Fill Area

Edit the Fill

Once styled, you’re ready to move on!

Registering Input

We’ll jump straight into the coding and won’t cover how to set up Input Actions or scripts in this guide.

💡 Need help setting up Input Actions Scripts? [Click here]
💡 New to the Input System? [Start here].

First, we declare two global variables :

🔍 Code Breakdown:

_slider: A reference to your UI Slider, made accessible in the Inspector using [SerializeField].
_isSprinting: A flag to track whether the player is currently sprinting.

Input Callbacks

Using Unity’s event-based callback system, create two methods:

One for when sprint starts (key is pressed)
One for when sprint stops (key is released)

Note: When using event notation, Unity auto-generates the callback methods for you. Just press Tab and then Enter after referencing the action.

For now, test the callbacks by printing messages to the console.

Coding the Stamina Bar

🧠What we need: The slider value should decrease while sprinting and increase while resting.
💡Solution: Use a coroutine to update the slider value over time based on the _isSprinting state.

Sprint Start

Let’s create our coroutine. We’ll start by creating the condition to track when the Player is spriting.

Code Breakdown

By using the boolean variable we created earlier, we can now actively track when the player is sprinting.
While this variable is true, the stamina slider's value decreases over time—this is achieved using Time.deltaTime, which ensures the change is smooth and frame-rate independent.
A Debug.Log statement is included to display the slider value during development for troubleshooting purposes. Be sure to remove it in the final version of your code.
Typically, coroutines use yield return new WaitForSeconds() to introduce a delay between executions. However, since our logic needs to update every frame without a fixed delay, we use yield return null instead. This keeps the coroutine running continuously, once per frame.

Sprint Cancel

Continuing within the same coroutine, we add logic to increase the slider value whenever the boolean is false.

The coroutine as a whole should look like this:

Executing the Sprint Action and the Interactive Stamina Bar

In your sprint start and cancel methods, update the _isSprinting flag and start the coroutine. The coroutine is only called from the Start method.

🔍 Code Breakdown:

The boolean is set to true when the sprint key is pressed, and false when it’s released.
We call the coroutine from the start input method to ensure the stamina bar responds appropriately—decreasing while sprinting and recharging when the key is no longer held.

Bonus Code Tip on Courtines:

If you want to control how long it takes for the coroutine to decrease or increase, simply divide the values by the number of seconds.

The Result

When divided by 10, the refill speed is noticeably slower. (Note: The GIF is cut short to keep the file size down — it doesn’t instantly refill. What you’re seeing is the GIF looping.)

Thanks for reading!
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