Loading screens with coroutines in Unity - Mini Project: Build & Apply

Loading screens with coroutines

📖 Scenario: You are making a simple game in Unity. When the player moves to a new level, you want to show a loading screen. This screen will show a message while the game loads the new level in the background.

🎯 Goal: You will create a loading screen using a coroutine. The coroutine will wait for 3 seconds to simulate loading, then hide the loading screen.

📋 What You'll Learn

Create a GameObject variable called loadingScreen to hold the loading screen panel.

Create a float variable called loadingTime and set it to 3.

Write a coroutine method called LoadLevel that waits for loadingTime seconds.

Show the loading screen before waiting and hide it after waiting.

Start the coroutine LoadLevel in the Start method.

Print Loading complete! after loading finishes.

💡 Why This Matters

🌍 Real World

Loading screens are common in games and apps to keep users informed while content loads.

💼 Career

Understanding coroutines and UI control is important for game developers and interactive app creators.

1

Create loading screen variable

Create a public GameObject variable called loadingScreen to hold the loading screen panel.

Unity

using UnityEngine;

public class LoadingManager : MonoBehaviour
{
    // Create a public GameObject variable called loadingScreen
    // Your code here
}

Hint

Use public GameObject loadingScreen; inside the class.

2

Add loading time variable

Add a public float variable called loadingTime and set it to 3f.

Unity

using UnityEngine;

public class LoadingManager : MonoBehaviour
{
    public GameObject loadingScreen;
    // Add a public float variable called loadingTime and set it to 3f
    // Your code here
}

Hint

Write public float loadingTime = 3f; inside the class.

3

Write the LoadLevel coroutine

Write a coroutine method called LoadLevel that does the following:
1. Sets loadingScreen.SetActive(true) to show the loading screen.
2. Waits for loadingTime seconds using yield return new WaitForSeconds(loadingTime);.
3. Sets loadingScreen.SetActive(false) to hide the loading screen.
4. Prints Loading complete! using Debug.Log.

Unity

using UnityEngine;
using System.Collections;

public class LoadingManager : MonoBehaviour
{
    public GameObject loadingScreen;
    public float loadingTime = 3f;

    // Write the LoadLevel coroutine method below
    // Your code here
}

Hint

Remember to use IEnumerator and yield return new WaitForSeconds(loadingTime); inside the coroutine.

4

Start the coroutine in Start method

Add a Start method that starts the coroutine LoadLevel using StartCoroutine(LoadLevel());.

Unity

using UnityEngine;
using System.Collections;

public class LoadingManager : MonoBehaviour
{
    public GameObject loadingScreen;
    public float loadingTime = 3f;

    public IEnumerator LoadLevel()
    {
        loadingScreen.SetActive(true);
        yield return new WaitForSeconds(loadingTime);
        loadingScreen.SetActive(false);
        Debug.Log("Loading complete!");
    }

    // Add the Start method below to start the coroutine
    // Your code here
}

Hint

Use void Start() and inside it call StartCoroutine(LoadLevel());.

Practice

1. What is the main purpose of using coroutines for loading screens in Unity?

easy

A. To run loading tasks without freezing the game UI

B. To speed up the loading process by using multiple threads

C. To automatically optimize game assets during loading

D. To replace the Update() method for all game logic

Solution

1. Step 1: Understand coroutine behavior

   Coroutines allow tasks to run over multiple frames without blocking the main thread.

2. Step 2: Relate to loading screens

   Using coroutines for loading lets the UI remain responsive and update progress smoothly.

3. Final Answer:

   To run loading tasks without freezing the game UI -> Option A

4. Quick Check:

   Coroutines keep UI responsive during loading = A [OK]

Hint: Coroutines prevent freezing by spreading work over frames [OK]

Common Mistakes:

• Thinking coroutines run on separate threads
• Believing coroutines speed up loading automatically
• Confusing coroutines with Update() method

2. Which of the following is the correct way to start a coroutine named LoadSceneAsync in Unity?

easy

A. StartCoroutine(LoadSceneAsync());

B. StartCoroutine(LoadSceneAsync);

C. StartCoroutine("LoadSceneAsync");

D. StartCoroutine.LoadSceneAsync();

Solution

1. Step 1: Recall coroutine syntax

   Coroutines are started by calling StartCoroutine with the IEnumerator method invoked, like StartCoroutine(MethodName()).

2. Step 2: Check options

   StartCoroutine(LoadSceneAsync()); correctly calls StartCoroutine with LoadSceneAsync() including parentheses.

3. Final Answer:

   StartCoroutine(LoadSceneAsync()); -> Option A

4. Quick Check:

   StartCoroutine needs method call with parentheses = A [OK]

Hint: StartCoroutine requires parentheses to call the IEnumerator method [OK]

Common Mistakes:

• Omitting parentheses when calling the coroutine method
• Using string names instead of method calls
• Trying to call coroutine like a normal method

3. Given this coroutine code snippet, what will be printed to the console?

IEnumerator LoadScene()
{
    AsyncOperation asyncLoad = SceneManager.LoadSceneAsync("GameScene");
    while (!asyncLoad.isDone)
    {
        Debug.Log($"Loading progress: {asyncLoad.progress * 100}%");
        yield return null;
    }
    Debug.Log("Loading complete!");
}

medium

A. Loading progress: 0% ... Loading progress: 100% ... Loading complete!

B. Loading progress: 0% ... Loading progress: 50% ... Loading complete!

C. Loading progress: 0% ... Loading progress: 90% ... Loading complete!

D. Only "Loading complete!" is printed

Solution

1. Step 1: Understand AsyncOperation progress

   AsyncOperation.progress goes from 0 to 0.9 during loading; it reaches 0.9 before isDone becomes true.

2. Step 2: Analyze the loop output

   The loop prints progress from 0% up to 90%, then exits when isDone is true, printing "Loading complete!".

3. Final Answer:

   Loading progress: 0% ... Loading progress: 90% ... Loading complete! -> Option C

4. Quick Check:

   AsyncOperation.progress maxes at 0.9 before done = C [OK]

Hint: AsyncOperation.progress maxes at 0.9 before completion [OK]

Common Mistakes:

• Assuming progress reaches 100% before isDone
• Expecting progress to jump directly to 100%
• Ignoring that isDone triggers after 90% progress

4. Identify the error in this coroutine code for a loading screen:

IEnumerator LoadLevel()
{
    AsyncOperation asyncLoad = SceneManager.LoadSceneAsync("Level1");
    while (asyncLoad.isDone == false)
    {
        progressBar.fillAmount = asyncLoad.progress;
        yield return new WaitForSeconds(1);
    }
}

medium

A. AsyncOperation.progress should be multiplied by 100

B. The while loop condition should be asyncLoad.isDone == true

C. The coroutine never yields control to the main thread

D. Using WaitForSeconds delays UI updates unnecessarily

Solution

1. Step 1: Check yield statement impact

   Using yield return new WaitForSeconds(1) pauses the coroutine for 1 second each loop, causing slow UI updates.

2. Step 2: Suggest better yield usage

   Yielding null (yield return null) updates every frame, making progress bar smoother and more responsive.

3. Final Answer:

   Using WaitForSeconds delays UI updates unnecessarily -> Option D

4. Quick Check:

   WaitForSeconds slows progress updates = B [OK]

Hint: Use yield return null for smooth frame-by-frame updates [OK]

Common Mistakes:

• Confusing progress value scale
• Changing loop condition incorrectly
• Not yielding at all causing freeze

5. You want to create a loading screen that shows a progress bar and a "Loading..." text that updates smoothly while loading a scene asynchronously. Which approach correctly combines coroutines and UI updates?

hard

A. Load the scene synchronously and update UI after loading finishes

B. Start a coroutine that updates progressBar.fillAmount with asyncLoad.progress every frame and updates loadingText with percentage until asyncLoad.isDone is true

C. Start a coroutine that waits 5 seconds then sets progressBar.fillAmount to 1 and loadingText to "Done"

D. Use Update() method to check asyncLoad.progress and update UI, no coroutine needed

Solution

1. Step 1: Understand asynchronous loading with UI updates

   Using a coroutine to check asyncLoad.progress each frame allows smooth progress bar and text updates during loading.

2. Step 2: Evaluate options for UI responsiveness

   Start a coroutine that updates progressBar.fillAmount with asyncLoad.progress every frame and updates loadingText with percentage until asyncLoad.isDone is true correctly updates UI every frame until loading completes; other options either block UI or do not update smoothly.

3. Final Answer:

   Start a coroutine that updates progressBar.fillAmount with asyncLoad.progress every frame and updates loadingText with percentage until asyncLoad.isDone is true -> Option B

4. Quick Check:

   Coroutine + frame updates = smooth loading UI = D [OK]

Hint: Update UI inside coroutine each frame until loading completes [OK]

Common Mistakes:

• Using synchronous loading blocking UI
• Not updating UI every frame
• Waiting fixed time instead of checking progress