Touch input basics in Unity

Introduction

Touch input lets your app know when and where someone touches the screen. It helps make games and apps interactive on phones and tablets.

You want to detect when a player taps the screen to jump in a game.

You want to drag an object by touching and moving your finger.

You want to detect multiple fingers touching at the same time for gestures.

You want to respond when the user swipes across the screen.

You want to create buttons that react to finger touches.

Syntax

Unity

if (Input.touchCount > 0) {
    Touch touch = Input.GetTouch(0);
    if (touch.phase == TouchPhase.Began) {
        // Code for when touch starts
    }
}

Input.touchCount tells how many fingers are touching the screen.

Input.GetTouch(index) gets info about a specific touch.

Examples

This checks if the screen was just touched and prints a message.

Unity

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

This loops through all touches and prints their positions.

Unity

for (int i = 0; i < Input.touchCount; i++) {
    Touch touch = Input.GetTouch(i);
    Debug.Log($"Touch {i} position: {touch.position}");
}

This detects when a finger moves and shows how far it moved.

Unity

Touch touch = Input.GetTouch(0);
if (touch.phase == TouchPhase.Moved) {
    Vector2 delta = touch.deltaPosition;
    Debug.Log($"Finger moved by {delta}");
}

Sample Program

This program checks the first finger touching the screen. It prints messages when the touch starts, moves, or ends, showing the position or movement.

Unity

using UnityEngine;

public class TouchExample : MonoBehaviour {
    void Update() {
        if (Input.touchCount > 0) {
            Touch touch = Input.GetTouch(0);
            if (touch.phase == TouchPhase.Began) {
                Debug.Log($"Touch started at {touch.position}");
            } else if (touch.phase == TouchPhase.Moved) {
                Debug.Log($"Touch moved by {touch.deltaPosition}");
            } else if (touch.phase == TouchPhase.Ended) {
                Debug.Log("Touch ended");
            }
        }
    }
}

Important Notes

Touch positions are in pixels from the bottom-left corner of the screen.

Touch phases include Began, Moved, Stationary, Ended, and Canceled.

Use Input.touchCount to avoid errors when no fingers are touching.

Summary

Touch input lets you detect finger actions on the screen.

Use Input.touchCount and Input.GetTouch to read touches.

Check touch.phase to know if a touch started, moved, or ended.

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