Responsive dimensions (Dimensions API) in React Native - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the Dimensions API from React Native.

React Native

import [1] from 'react-native';

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

AStyleSheet

BView

CDimensions

DText

Attempts:

3 left

💡 Hint

Common Mistakes

Importing View or Text instead of Dimensions.

Forgetting to import Dimensions before using it.

The Dimensions API is imported from 'react-native' to access screen size information.

2fill in blank

medium

Complete the code to get the screen width using Dimensions.

React Native

const screenWidth = Dimensions.[1]('window').width;

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

AgetSize

BgetDimensions

CgetWindow

Dget

Attempts:

3 left

💡 Hint

Common Mistakes

Using a method name that does not exist like getSize or getWindow.

Confusing the method with other APIs.

The get method of Dimensions returns an object with width and height of the screen.

3fill in blank

hard

Fix the error in the code to correctly get the screen height.

React Native

const screenHeight = Dimensions.get('window').[1];

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

Aheight

Bheightt

Cheigth

Dheigh

Attempts:

3 left

💡 Hint

Common Mistakes

Misspelling the property name causing undefined values.

Using similar but incorrect spellings.

The correct property name is height to get the screen height.

4fill in blank

hard

Fill both blanks to create a style that sets width and height to half the screen size.

React Native

const styles = StyleSheet.create({
  box: {
    width: screenWidth [1] 2,
    height: screenHeight [2] 2
  }
});

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

A/

B*

C-

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using multiplication or addition instead of division.

Using subtraction which would reduce size incorrectly.

To get half the screen size, divide the width and height by 2 using the / operator.

5fill in blank

hard

Fill all three blanks to create a responsive square view with side length equal to screen width minus 40.

React Native

const boxSize = screenWidth [1] 40;
const styles = StyleSheet.create({
  square: {
    width: boxSize,
    height: [2],
    backgroundColor: 'skyblue'
  }
});

// Use <View style=[3] /> to render

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

A-

BboxSize

Cstyles.square

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using addition instead of subtraction for size calculation.

Setting height to a wrong variable or number.

Not applying the style correctly to the View.

Subtract 40 from screenWidth to get boxSize. Set height equal to boxSize for a square. Use styles.square to style the View.

Practice

1. What does Dimensions.get('window') return in React Native?

easy

A. An object with screen width and height

B. A function to change screen size

C. A string describing device type

D. A boolean indicating orientation

Solution

1. Step 1: Understand Dimensions API purpose

   The Dimensions API provides device screen information.

2. Step 2: Identify what get('window') returns

   It returns an object containing width and height of the window.

3. Final Answer:

   An object with screen width and height -> Option A

4. Quick Check:

   Dimensions.get('window') = object with width and height [OK]

Hint: Remember: get('window') gives width and height object [OK]

Common Mistakes:

• Thinking it returns a function
• Confusing it with device type string
• Assuming it returns orientation boolean

2. Which of the following is the correct syntax to import the Dimensions API in React Native?

easy

A. import { Dimensions } from 'react-native';

B. import { Dimensions } from 'Dimensions';

C. import Dimensions from 'Dimensions';

D. import Dimensions from 'react-native';

Solution

1. Step 1: Recall React Native import style

   React Native exports Dimensions as a named export.

2. Step 2: Choose correct import syntax

   Correct syntax is: import { Dimensions } from 'react-native';

3. Final Answer:

   import { Dimensions } from 'react-native'; -> Option A

4. Quick Check:

   Named import from 'react-native' = import { Dimensions } from 'react-native'; [OK]

Hint: Use curly braces for named imports from react-native [OK]

Common Mistakes:

• Using default import without braces
• Importing from wrong module name
• Confusing named and default imports

3. Given the code snippet:

const { width, height } = Dimensions.get('window');
const boxWidth = width * 0.5;
console.log(boxWidth);

If the device screen width is 360 pixels, what will be logged?

medium

A. 0.5

B. 720

C. 360

D. 180

Solution

1. Step 1: Extract width from Dimensions

   width is 360 pixels as given.

2. Step 2: Calculate boxWidth as half of width

   boxWidth = 360 * 0.5 = 180 pixels.

3. Final Answer:

   180 -> Option D

4. Quick Check:

   360 * 0.5 = 180 [OK]

Hint: Multiply width by fraction to get responsive size [OK]

Common Mistakes:

• Confusing multiplication with addition
• Using height instead of width
• Misreading 0.5 as 5

4. What is wrong with this code snippet?

import { Dimensions } from 'react-native';
const { width, height } = Dimensions.get('screen');
const boxHeight = width * 0.3;
console.log(boxHeight);

medium

A. Missing semicolon after import statement

B. Using 'screen' instead of 'window' may cause unexpected layout issues

C. Cannot destructure width and height from Dimensions.get()

D. Multiplying width by 0.3 is invalid

Solution

1. Step 1: Understand difference between 'screen' and 'window'

   'screen' includes status bar and navigation, 'window' excludes them.

2. Step 2: Identify impact on layout

   Using 'screen' may cause layout to not fit visible area properly.

3. Final Answer:

   Using 'screen' instead of 'window' may cause unexpected layout issues -> Option B

4. Quick Check:

   'screen' vs 'window' affects layout size [OK]

Hint: Use 'window' for layout size, not 'screen' [OK]

Common Mistakes:

• Thinking 'screen' and 'window' are the same
• Ignoring layout issues from status bar
• Assuming destructuring is invalid

5. You want a square box that always fills 40% of the screen width and adjusts height accordingly on device rotation. Which approach is best?

hard

A. Use fixed width and height values in styles

B. Use Dimensions.get('window') once at app start

C. Use useWindowDimensions hook to get width and set height equal to width * 0.4

D. Use Dimensions.get('screen') and hardcode height

Solution

1. Step 1: Understand requirement for dynamic size on rotation

   Fixed values or one-time get won't update on rotation.

2. Step 2: Choose hook that updates on dimension changes

   useWindowDimensions hook updates width and height on rotation.

3. Step 3: Calculate height based on current width

   Set height = width * 0.4 to keep square shape responsive.

4. Final Answer:

   Use useWindowDimensions hook to get width and set height equal to width * 0.4 -> Option C

5. Quick Check:

   Dynamic hook + calculation = responsive square [OK]

Hint: Use useWindowDimensions for responsive updates on rotation [OK]

Common Mistakes:

• Using fixed sizes that don't update
• Using Dimensions.get only once
• Confusing 'screen' with 'window' for layout