Modal and bottom sheet in React Native - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a Modal in React Native?

A Modal is a component that appears on top of the current screen to show important information or get user input. It blocks interaction with the rest of the app until dismissed.

beginner

How does a Bottom Sheet differ from a Modal?

A Bottom Sheet slides up from the bottom of the screen and usually covers part of the screen. It is less intrusive than a Modal and often used for actions or options.

beginner

Which React Native component is used to create a Modal?

The built-in Modal component is used to create modals in React Native.

beginner

What prop controls the visibility of a Modal in React Native?

The visible prop controls whether the Modal is shown (true) or hidden (false).

intermediate

Name one popular library to implement Bottom Sheets in React Native.

One popular library is reanimated-bottom-sheet or @gorhom/bottom-sheet which provide customizable bottom sheets.

What happens when a Modal is visible in React Native?

A It allows interaction with the background screen.

B It blocks interaction with the rest of the app until dismissed.

C It automatically closes after 5 seconds.

D It moves the screen content to the top.

A Modal blocks interaction with the rest of the app until the user dismisses it.

Which prop do you use to show or hide a Modal?

A show

B display

C active

D visible

The visible prop controls the Modal's visibility.

A Bottom Sheet usually appears from where on the screen?

A Top

B Left

C Bottom

D Center

A Bottom Sheet slides up from the bottom of the screen.

Which React Native component is built-in for Modals?

A Modal

B Popup

C Dialog

D Sheet

React Native provides a built-in Modal component.

Which library can help create Bottom Sheets in React Native?

A reanimated-bottom-sheet

B axios

C redux

D react-navigation

reanimated-bottom-sheet is a popular library for Bottom Sheets.

Explain how a Modal works in React Native and when you might use it.

Think about a popup that stops you from using the app until you respond.

Describe the difference between a Modal and a Bottom Sheet in mobile apps.

Imagine a popup vs a sliding panel from the bottom.

Practice

1. What is the main purpose of a Modal component in React Native?

easy

A. To display content over the current screen and keep user focus

B. To navigate between different screens

C. To create a permanent footer on the screen

D. To handle background tasks silently

Solution

1. Step 1: Understand what a Modal does

   A Modal appears on top of the current screen and blocks interaction with the background.

2. Step 2: Compare options

   Only To display content over the current screen and keep user focus describes this behavior correctly; others describe unrelated features.

3. Final Answer:

   To display content over the current screen and keep user focus -> Option A

4. Quick Check:

   Modal = Overlay content [OK]

Hint: Modals block background, focus user attention [OK]

Common Mistakes:

• Confusing Modal with navigation
• Thinking Modal is a footer or background task
• Assuming Modal is always full screen

2. Which of the following is the correct way to control the visibility of a Modal in React Native?

easy

A. <Modal show={true}>

B. <Modal visible={true}>

C. <Modal isVisible={true}>

D. <Modal display={true}>

Solution

1. Step 1: Recall the correct prop for Modal visibility

   The React Native Modal uses the visible prop to show or hide the modal.

2. Step 2: Check each option

   Only <Modal visible={true}> uses visible correctly; others use incorrect prop names.

3. Final Answer:

   <Modal visible={true}> -> Option B

4. Quick Check:

   Modal visibility prop = visible [OK]

Hint: Use visible prop to toggle Modal display [OK]

Common Mistakes:

• Using show or isVisible instead of visible
• Confusing display with visible
• Forgetting to pass boolean value

3. What will happen when the following React Native code runs?

const [modalVisible, setModalVisible] = React.useState(false);

return (
  <>
    <Button title="Show Modal" onPress={() => setModalVisible(true)} />
    <Modal visible={modalVisible} animationType="slide">
      <View>
        <Text>Hello Modal</Text>
        <Button title="Close" onPress={() => setModalVisible(false)} />
      </View>
    </Modal>
  </>
);

medium

A. The modal appears sliding up when 'Show Modal' is pressed and closes when 'Close' is pressed

B. The modal appears instantly without animation

C. The modal never appears because visible is false initially

D. The modal is always visible and cannot be closed

Solution

1. Step 1: Understand state controlling Modal visibility

   The state variable modalVisible starts false, so modal is hidden initially.

2. Step 2: Analyze button actions

   Pressing 'Show Modal' sets modalVisible to true, showing modal with slide animation. 'Close' button sets it back to false, hiding modal.

3. Final Answer:

   The modal appears sliding up when 'Show Modal' is pressed and closes when 'Close' is pressed -> Option A

4. Quick Check:

   State controls visible with animation [OK]

Hint: State true shows modal; false hides it [OK]

Common Mistakes:

• Assuming modal shows without pressing button
• Ignoring animationType effect
• Thinking modal cannot be closed

4. Identify the error in this React Native Modal usage:

const [show, setShow] = React.useState(false);

return (
  <Modal visible={show} animationType="fade" onRequestClose={() => setShow(false)}>
    <View>
      <Text>Modal Content</Text>
    </View>
  </Modal>
  <Button title="Open" onPress={() => setShow(true)} />
);

medium

A. The onRequestClose prop is missing

B. The Button component is outside the Modal and will not render

C. Modal must be wrapped inside a single parent element

D. The visible prop should be a string, not boolean

Solution

1. Step 1: Check JSX structure

   The return statement has two sibling elements: Modal and Button, which is invalid JSX without a wrapper.

2. Step 2: Identify correct fix

   Wrapping Modal and Button inside a fragment or View fixes the error.

3. Final Answer:

   Modal must be wrapped inside a single parent element -> Option C

4. Quick Check:

   JSX requires one parent element [OK]

Hint: Wrap siblings in a fragment or View [OK]

Common Mistakes:

• Ignoring JSX syntax rules
• Thinking onRequestClose is optional on Android
• Confusing visible prop type

5. You want to create a bottom sheet modal that slides up from the bottom and closes when tapping outside it. Which combination of props and components achieves this behavior in React Native?

hard

A. Use Modal visible={false} animationType="slide" transparent={true} with no tap detection

B. Use Modal visible={true} animationType="fade" without transparent prop and no tap detection

C. Use Modal visible={true} animationType="none" transparent={false} with a Button inside

D. Use Modal visible={true} animationType="slide" transparent={true} with a TouchableWithoutFeedback wrapping the background to detect taps

Solution

1. Step 1: Understand bottom sheet modal requirements

   It must slide up (animationType="slide"), be transparent so background is visible, and detect taps outside to close.

2. Step 2: Identify correct props and components

   Using transparent={true} allows background taps. Wrapping background in TouchableWithoutFeedback lets you detect taps to close modal.

3. Step 3: Eliminate wrong options

   Options B, C, and D miss transparency, correct animation, or tap detection.

4. Final Answer:

   Use <Modal visible={true} animationType="slide" transparent={true}> with a TouchableWithoutFeedback wrapping the background to detect taps -> Option D

5. Quick Check:

   Slide + transparent + tap detection = bottom sheet [OK]

Hint: Slide + transparent + tap outside closes modal [OK]

Common Mistakes:

• Forgetting transparent prop for background tap
• Using fade animation instead of slide
• Not handling tap outside to close