Keyboard input (GetKey, GetKeyDown) in Unity

Introduction

We use keyboard input to let players control the game by pressing keys. GetKey checks if a key is held down, and GetKeyDown checks if a key was just pressed once.

Move a character continuously while a key is held down, like walking forward.

Trigger an action only once when a key is first pressed, like jumping.

Detect if a key is being held to charge a power or run faster.

Pause the game when the player presses the Escape key once.

Syntax

Unity

Input.GetKey(KeyCode.KeyName)
Input.GetKeyDown(KeyCode.KeyName)

GetKey returns true every frame the key is held down.

GetKeyDown returns true only on the first frame the key is pressed.

Examples

This moves the player forward as long as the W key is pressed.

Unity

if (Input.GetKey(KeyCode.W)) {
    // Move forward while W is held
}

This triggers a jump only once when the Space key is pressed.

Unity

if (Input.GetKeyDown(KeyCode.Space)) {
    // Jump once when Space is pressed
}

Holding Left Shift makes the player run faster.

Unity

if (Input.GetKey(KeyCode.LeftShift)) {
    // Run faster while holding Left Shift
}

Sample Program

This script prints "Moving forward" every frame while the W key is held down, and prints "Jump!" once when the Space key is pressed.

Unity

using UnityEngine;

public class PlayerController : MonoBehaviour
{
    void Update()
    {
        if (Input.GetKey(KeyCode.W))
        {
            Debug.Log("Moving forward");
        }

        if (Input.GetKeyDown(KeyCode.Space))
        {
            Debug.Log("Jump!");
        }
    }
}

Important Notes

Use GetKeyDown for actions that should happen once per key press.

Use GetKey for continuous actions while the key is held.

Remember to check input inside the Update() method so it runs every frame.

Summary

GetKey detects if a key is held down continuously.

GetKeyDown detects the moment a key is first pressed.

Use these to control player actions smoothly and responsively.

Practice

1. What does Input.GetKeyDown(KeyCode.Space) detect in Unity?

easy

A. If the space key is being held down continuously

B. If any key is pressed

C. If the space key is released

D. The exact frame when the space key is first pressed

Solution

1. Step 1: Understand GetKeyDown behavior

   Input.GetKeyDown returns true only on the first frame the key is pressed.

2. Step 2: Apply to space key

   When KeyCode.Space is used, it detects the first press of the space bar only.

3. Final Answer:

   The exact frame when the space key is first pressed -> Option D

4. Quick Check:

   GetKeyDown = first press frame [OK]

Hint: GetKeyDown triggers only once on key press [OK]

Common Mistakes:

• Confusing GetKeyDown with GetKey
• Thinking it detects key release
• Assuming it detects any key

2. Which of the following is the correct syntax to check if the "W" key is being held down in Unity?

easy

A. Input.GetKey(KeyCode.W)

B. Input.GetKeyDown(KeyCode.W)

C. Input.GetKeyUp(KeyCode.W)

D. Input.IsKeyPressed(KeyCode.W)

Solution

1. Step 1: Identify method for continuous key hold

   Input.GetKey returns true every frame the key is held down.

2. Step 2: Match syntax for "W" key

   The correct syntax is Input.GetKey(KeyCode.W) to check if "W" is held.

3. Final Answer:

   Input.GetKey(KeyCode.W) -> Option A

4. Quick Check:

   GetKey = held down check [OK]

Hint: Use GetKey for continuous key press detection [OK]

Common Mistakes:

• Using GetKeyDown instead of GetKey for hold detection
• Using non-existent method IsKeyPressed
• Confusing GetKeyUp with GetKey

3. What will be printed if the following Unity code runs and the player holds down the "A" key for 3 seconds?

void Update() {
  if (Input.GetKeyDown(KeyCode.A)) {
    Debug.Log("Pressed A");
  }
  if (Input.GetKey(KeyCode.A)) {
    Debug.Log("Holding A");
  }
}

medium

A. "Pressed A" printed many times, "Holding A" once

B. "Pressed A" and "Holding A" printed once each

C. "Pressed A" once and "Holding A" many times over 3 seconds

D. No output because GetKeyDown doesn't detect held keys

Solution

1. Step 1: Understand GetKeyDown behavior

   Input.GetKeyDown(KeyCode.A) triggers only once when the key is first pressed.

2. Step 2: Understand GetKey behavior

   Input.GetKey(KeyCode.A) triggers every frame while the key is held down, so it prints repeatedly during 3 seconds.

3. Final Answer:

   "Pressed A" once and "Holding A" many times over 3 seconds -> Option C

4. Quick Check:

   GetKeyDown = once, GetKey = continuous [OK]

Hint: GetKeyDown prints once; GetKey prints repeatedly while held [OK]

Common Mistakes:

• Thinking GetKeyDown prints repeatedly
• Confusing GetKey with GetKeyDown
• Assuming no output for held keys

4. Identify the error in this Unity code snippet:

void Update() {
  if (Input.GetKeyDown("space")) {
    Debug.Log("Jump!");
  }
}

medium

A. The code is correct and will print "Jump!"

B. GetKeyDown requires a KeyCode, not a string

C. The method name should be GetKeyUp

D. Debug.Log cannot be called inside Update

Solution

1. Step 1: Verify GetKeyDown parameter

   Input.GetKeyDown requires a KeyCode parameter, not a string like "space".

2. Step 2: Confirm error

   Passing a string will cause a compile-time error; the correct usage is Input.GetKeyDown(KeyCode.Space).

3. Final Answer:

   GetKeyDown requires a KeyCode, not a string -> Option B

4. Quick Check:

   GetKeyDown("space") is invalid [OK]

Hint: GetKeyDown requires KeyCode enum, not string [OK]

Common Mistakes:

• Believing GetKeyDown accepts strings
• Thinking Debug.Log can't be in Update
• Suggesting GetKeyUp instead

5. You want to make a player jump only once when the spacebar is pressed, but also allow holding the left arrow key to move continuously. Which code snippet correctly implements this behavior?

void Update() {
  // Your code here
}

hard

A. if (Input.GetKeyDown(KeyCode.Space)) { Jump(); } if (Input.GetKey(KeyCode.LeftArrow)) { MoveLeft(); }

B. if (Input.GetKey(KeyCode.Space)) { Jump(); } if (Input.GetKeyDown(KeyCode.LeftArrow)) { MoveLeft(); }

C. if (Input.GetKeyUp(KeyCode.Space)) { Jump(); } if (Input.GetKey(KeyCode.LeftArrow)) { MoveLeft(); }

D. if (Input.GetKeyDown(KeyCode.Space)) { Jump(); } if (Input.GetKeyDown(KeyCode.LeftArrow)) { MoveLeft(); }

Solution

1. Step 1: Use GetKeyDown for single jump press

   Jump should trigger once when spacebar is first pressed, so use Input.GetKeyDown(KeyCode.Space).

2. Step 2: Use GetKey for continuous left movement

   Holding left arrow should move continuously, so use Input.GetKey(KeyCode.LeftArrow).

3. Final Answer:

   if (Input.GetKeyDown(KeyCode.Space)) { Jump(); } if (Input.GetKey(KeyCode.LeftArrow)) { MoveLeft(); } -> Option A

4. Quick Check:

   Jump = GetKeyDown, Move = GetKey [OK]

Hint: Jump once with GetKeyDown; move continuously with GetKey [OK]

Common Mistakes:

• Using GetKey for jump causes repeated jumps
• Using GetKeyDown for movement causes single-step moves
• Using GetKeyUp incorrectly for jump