Touch input basics in Unity - Mini Project: Build & Apply

Touch Input Basics

📖 Scenario: You are creating a simple Unity app that reacts when the user touches the screen. This is common in mobile games and apps where touch controls are used.

🎯 Goal: Build a Unity script that detects when the user touches the screen and prints the touch position to the console.

📋 What You'll Learn

Create a list to store current touches

Create a variable to count the number of touches

Use a loop to check each touch's position

Print the touch positions to the console

💡 Why This Matters

🌍 Real World

Touch input is essential for mobile apps and games to respond to user finger taps and gestures.

💼 Career

Understanding touch input is key for mobile game developers and app creators working with Unity.

1

Create a list to hold current touches

Create a variable called touches and set it to Input.touches to get the current touches on the screen.

Unity

using UnityEngine;

public class TouchInput : MonoBehaviour
{
    void Update()
    {
        // Your code here
    }
}

Hint

Use Input.touches to get all current touches as an array.

2

Create a variable to count the number of touches

Create an integer variable called touchCount and set it to Input.touchCount to get how many touches are currently on the screen.

Unity

using UnityEngine;

public class TouchInput : MonoBehaviour
{
    void Update()
    {
        Touch[] touches = Input.touches;
        // Create touchCount variable here
    }
}

Hint

Input.touchCount gives the number of touches currently detected.

3

Loop through each touch and get its position

Use a for loop with variable i from 0 to touchCount (exclusive) to access each touch in touches. Inside the loop, create a variable touchPos and set it to touches[i].position.

Unity

using UnityEngine;

public class TouchInput : MonoBehaviour
{
    void Update()
    {
        Touch[] touches = Input.touches;
        int touchCount = Input.touchCount;
        // Loop through touches and get position
    }
}

Hint

Use a for loop to go through each touch and get its position.

4

Print each touch position to the console

Inside the for loop, add a line to print the text "Touch position: " followed by the touchPos variable using Debug.Log.

Unity

using UnityEngine;

public class TouchInput : MonoBehaviour
{
    void Update()
    {
        Touch[] touches = Input.touches;
        int touchCount = Input.touchCount;
        for (int i = 0; i < touchCount; i++)
        {
            Vector2 touchPos = touches[i].position;
            // Print touchPos here
        }
    }
}

Hint

Use Debug.Log("Touch position: " + touchPos); to print the position.

Practice

1. Which Unity property tells you how many fingers are currently touching the screen?

easy

A. Input.touchPhase

B. Input.touchCount

C. Input.GetTouchCount()

D. Input.touchPosition

Solution

1. Step 1: Understand the purpose of Input.touchCount

   This property returns the number of fingers currently touching the screen in Unity.

2. Step 2: Compare with other options

   Input.touchPhase is not a property but an enum for touch state; Input.GetTouchCount() does not exist; Input.touchPosition gives position, not count.

3. Final Answer:

   Input.touchCount -> Option B

4. Quick Check:

   Number of touches = Input.touchCount [OK]

Hint: Remember: touchCount counts fingers on screen [OK]

Common Mistakes:

• Confusing touchCount with touchPhase
• Using non-existent methods like GetTouchCount()
• Mixing position with count

2. Which of the following is the correct way to get the first touch input in Unity?

easy

A. Input.touch(0)

B. Input.GetTouchCount(0)

C. Input.GetTouch(0)

D. Input.touchCount(0)

Solution

1. Step 1: Recall the method to access touches

   Unity uses Input.GetTouch(index) to get a touch at a specific index.

2. Step 2: Check syntax correctness

   Input.touch(0) and Input.touchCount(0) are invalid; GetTouchCount(0) does not exist.

3. Final Answer:

   Input.GetTouch(0) -> Option C

4. Quick Check:

   First touch = Input.GetTouch(0) [OK]

Hint: Use GetTouch(index) to access specific touch [OK]

Common Mistakes:

• Using touch as a method instead of GetTouch
• Trying to call touchCount as a method
• Confusing method names

3. What will be the output of this code snippet if the user just started touching the screen?

if (Input.touchCount > 0) {
    Touch touch = Input.GetTouch(0);
    if (touch.phase == TouchPhase.Began) {
        Debug.Log("Touch started");
    }
}

medium

A. Touch ended

B. Touch moved

C. No output

D. Touch started

Solution

1. Step 1: Understand the touch.phase check

   The code checks if the first touch's phase is TouchPhase.Began, which means the touch just started.

2. Step 2: Match the condition with output

   If the user just started touching, the condition is true and "Touch started" is logged.

3. Final Answer:

   Touch started -> Option D

4. Quick Check:

   touch.phase == Began means "Touch started" [OK]

Hint: TouchPhase.Began means finger just touched screen [OK]

Common Mistakes:

• Confusing Began with Moved or Ended
• Ignoring touchCount check
• Assuming output without touch

4. Identify the error in this Unity C# code snippet for detecting a touch:

if (Input.touchCount > 0) {
    Touch touch = Input.GetTouch(0);
    if (touch.phase = TouchPhase.Began) {
        Debug.Log("Touch started");
    }
}

medium

A. Using assignment (=) instead of comparison (==) in if condition

B. Incorrect method name GetTouch instead of GetTouches

C. Missing check for touchCount == 1

D. TouchPhase.Began is not a valid enum

Solution

1. Step 1: Check the if condition syntax

   The condition uses a single equals sign (=), which assigns instead of compares.

2. Step 2: Understand correct comparison operator

   To compare values, double equals (==) must be used in C#.

3. Final Answer:

   Using assignment (=) instead of comparison (==) in if condition -> Option A

4. Quick Check:

   Use == to compare, not = [OK]

Hint: Use == for comparison, = is assignment [OK]

Common Mistakes:

• Using = instead of == in conditions
• Thinking GetTouch is wrong method
• Unnecessary touchCount == 1 check
• Misunderstanding TouchPhase enum

5. You want to detect when the user moves their finger on the screen and print the new position. Which code snippet correctly does this inside Update()?

hard

A. if (Input.touchCount > 0) {
Touch touch = Input.GetTouch(0);
if (touch.phase == TouchPhase.Moved) {
Debug.Log($"Moved to: {touch.position}");
}
}

B. if (Input.touchCount > 0) {
Touch touch = Input.GetTouch(0);
if (touch.phase == TouchPhase.Ended) {
Debug.Log($"Moved to: {touch.position}");
}
}

C. if (Input.touchCount == 0) {
Touch touch = Input.GetTouch(0);
Debug.Log($"Moved to: {touch.position}");
}

D. Touch touch = Input.GetTouch(0);
if (touch.phase == TouchPhase.Moved) {
Debug.Log($"Moved to: {touch.position}");
}

Solution

1. Step 1: Check for active touches

   We must ensure Input.touchCount > 0 before accessing touches to avoid errors.

2. Step 2: Detect the move phase and print position

   Using touch.phase == TouchPhase.Moved correctly detects finger movement and prints the position.

3. Final Answer:

   Code snippet D correctly detects movement and prints position -> Option A

4. Quick Check:

   Check touchCount > 0 and phase == Moved [OK]

Hint: Always check touchCount > 0 before GetTouch [OK]

Common Mistakes:

• Checking phase == Ended instead of Moved
• Accessing GetTouch(0) when touchCount == 0
• Not checking touchCount before GetTouch