Touch input basics in Unity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the screen is touched.

Unity

if (Input.[1] > 0) {
    Debug.Log("Screen touched");
}

Drag options to blanks, or click blank then click option'

AtouchPhase

Btouches

CtouchCount

DtouchPosition

Attempts:

3 left

💡 Hint

Common Mistakes

Using Input.touches instead of Input.touchCount

Using Input.touchPhase which is not a property of Input

The Input.touchCount property returns the number of touches currently on the screen.

2fill in blank

medium

Complete the code to get the position of the first touch on the screen.

Unity

Vector2 touchPos = Input.touches[[1]].position;

Drag options to blanks, or click blank then click option'

A0

B1

C-1

DtouchCount

Attempts:

3 left

💡 Hint

Common Mistakes

Using 1 instead of 0 as index

Using touchCount as index which is out of range

The first touch is at index 0 in the Input.touches array.

3fill in blank

hard

Fix the error in the code to detect if the first touch just began.

Unity

if (Input.touches[0].[1] == TouchPhase.Began) {
    Debug.Log("Touch started");
}

Drag options to blanks, or click blank then click option'

AtouchCount

Bphase

CdeltaPosition

Dposition

Attempts:

3 left

💡 Hint

Common Mistakes

Using position instead of phase

Using touchCount which is not a property of Touch

The phase property tells the current state of the touch, such as began, moved, or ended.

4fill in blank

hard

Fill both blanks to create a dictionary mapping fingerId to touch position for all touches.

Unity

var touchPositions = new Dictionary<int, Vector2>();
for (int i = 0; i < Input.touchCount; i++) {
    var touch = Input.touches[i];
    touchPositions[touch.[1]] = touch.[2];
}

Drag options to blanks, or click blank then click option'

AfingerId

Bposition

Cphase

DdeltaPosition

Attempts:

3 left

💡 Hint

Common Mistakes

Using phase or deltaPosition instead of position

Using touchCount instead of fingerId

Each touch has a unique fingerId and a position on the screen.

5fill in blank

hard

Fill all three blanks to detect a swipe by checking if the touch moved more than 50 pixels.

Unity

if (Input.touchCount > 0) {
    Touch touch = Input.touches[[1]];
    if (touch.phase == TouchPhase.[2]) {
        if (touch.[3].magnitude > 50) {
            Debug.Log("Swipe detected");
        }
    }
}

Drag options to blanks, or click blank then click option'

A0

BMoved

CdeltaPosition

DBegan

Attempts:

3 left

💡 Hint

Common Mistakes

Using phase Began instead of Moved

Using position instead of deltaPosition

Using wrong touch index

We check the first touch (index 0), see if it moved, and then check if the movement distance is greater than 50 pixels using deltaPosition.magnitude.

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