Dark mode support in Flutter - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to enable dark mode support in the MaterialApp widget.

Flutter

MaterialApp(
  title: 'My App',
  theme: ThemeData.light(),
  darkTheme: ThemeData.[1](),
  themeMode: ThemeMode.system,
  home: HomePage(),
)

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

Adark

BdarkMode

CdarkTheme

DdarkStyle

Attempts:

3 left

💡 Hint

Common Mistakes

Using ThemeData.darkMode() which does not exist.

Using ThemeData.darkTheme() which is incorrect.

The correct method to create a dark theme is ThemeData.dark().

2fill in blank

medium

Complete the code to set the app's theme mode to always use dark mode.

Flutter

MaterialApp(
  themeMode: ThemeMode.[1],
  home: HomePage(),
)

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

Asystem

Bauto

Clight

Ddark

Attempts:

3 left

💡 Hint

Common Mistakes

Using ThemeMode.system which follows device settings.

Using ThemeMode.light which forces light mode.

ThemeMode.dark forces the app to always use the dark theme.

3fill in blank

hard

Fix the error in the code to properly detect dark mode in a widget.

Flutter

bool isDark = MediaQuery.of(context).[1] == Brightness.dark;

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

AthemeBrightness

Bbrightness

CplatformBrightness

DdarkMode

Attempts:

3 left

💡 Hint

Common Mistakes

Using MediaQuery.of(context).brightness which does not exist.

Using 'darkMode' which is not a MediaQuery property.

MediaQuery.of(context).platformBrightness gives the current brightness mode of the device.

4fill in blank

hard

Fill both blanks to create a widget that changes text color based on dark mode.

Flutter

Text(
  'Hello',
  style: TextStyle(color: isDark ? [1] : [2]),
)

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

AColors.white

BColors.black

CColors.grey

DColors.blue

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same color for both modes causing poor contrast.

Using colors that are hard to read on dark or light backgrounds.

In dark mode, text color is usually white; in light mode, black.

5fill in blank

hard

Fill all three blanks to define a dark theme with primary color blue and scaffold background black.

Flutter

ThemeData(
  brightness: Brightness.[1],
  primaryColor: Colors.[2],
  scaffoldBackgroundColor: Colors.[3],
)

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

Adark

Bblue

Cblack

Dlight

Attempts:

3 left

💡 Hint

Common Mistakes

Using Brightness.light instead of dark.

Mixing colors that do not fit dark mode design.

Dark theme uses Brightness.dark, primary color blue, and black background for scaffold.

Practice

1. What is the main purpose of using darkTheme in a Flutter app?

easy

A. To define the app's appearance when the device is in dark mode

B. To disable dark mode support in the app

C. To set the default font style for the app

D. To create a theme for tablet devices only

Solution

1. Step 1: Understand the role of darkTheme

   The darkTheme property in MaterialApp defines how the app looks when dark mode is active.

2. Step 2: Compare with other theme properties

   The theme property is for light mode, and darkTheme is specifically for dark mode appearance.

3. Final Answer:

   To define the app's appearance when the device is in dark mode -> Option A

4. Quick Check:

   darkTheme sets dark mode style [OK]

Hint: Remember: darkTheme is for dark mode look [OK]

Common Mistakes:

• Confusing darkTheme with theme (light mode)
• Thinking darkTheme disables dark mode
• Assuming darkTheme affects only fonts

2. Which of the following is the correct way to enable dark mode support in MaterialApp?

easy

A. Set themeMode: ThemeMode.dark and provide darkTheme

B. Set theme: ThemeData.dark() only

C. Set darkTheme: ThemeData.light() only

D. Set themeMode: ThemeMode.light and provide darkTheme

Solution

1. Step 1: Identify how to activate dark mode

   Using themeMode: ThemeMode.dark tells Flutter to use the dark theme.

2. Step 2: Provide the dark theme style

   Providing darkTheme defines the dark mode appearance.

3. Final Answer:

   Set themeMode: ThemeMode.dark and provide darkTheme -> Option A

4. Quick Check:

   Enable dark mode with themeMode and darkTheme [OK]

Hint: Use themeMode with darkTheme to enable dark mode [OK]

Common Mistakes:

• Only setting theme without themeMode
• Using light theme in darkTheme property
• Setting themeMode to light but expecting dark mode

3. Given this Flutter code snippet, what will be the background color when the device is in dark mode?

MaterialApp(
  theme: ThemeData(primaryColor: Colors.white),
  darkTheme: ThemeData(primaryColor: Colors.black),
  themeMode: ThemeMode.system,
  home: Scaffold(
    backgroundColor: Theme.of(context).primaryColor,
  ),
)

medium

A. Blue (default)

B. White

C. Black

D. Transparent

Solution

1. Step 1: Understand themeMode.system behavior

   When themeMode is system, Flutter uses darkTheme if device is in dark mode.

2. Step 2: Check primaryColor in darkTheme

   The darkTheme sets primaryColor to black, so backgroundColor will be black.

3. Final Answer:

   Black -> Option C

4. Quick Check:

   System dark mode uses darkTheme colors [OK]

Hint: themeMode.system uses darkTheme on dark devices [OK]

Common Mistakes:

• Assuming theme (light) colors always apply
• Ignoring themeMode.system behavior
• Confusing primaryColor with backgroundColor default

4. You wrote this code but dark mode is not working as expected. What is the error?

MaterialApp(
  theme: ThemeData.light(),
  darkTheme: ThemeData.dark(),
  home: HomeScreen(),
)

medium

A. theme and darkTheme cannot be used together

B. Missing themeMode property to switch themes

C. Incorrect use of ThemeData.dark()

D. HomeScreen must be wrapped in a Theme widget

Solution

1. Step 1: Check themeMode usage

   Without themeMode, Flutter defaults to light mode and ignores darkTheme.

2. Step 2: Confirm darkTheme is correct

   ThemeData.dark() is valid, so no error there.

3. Final Answer:

   Missing themeMode property to switch themes -> Option B

4. Quick Check:

   themeMode is required to enable dark mode switching [OK]

Hint: Always set themeMode to enable dark mode [OK]

Common Mistakes:

• Forgetting to set themeMode
• Thinking darkTheme alone enables dark mode
• Wrapping home widget unnecessarily

5. You want your Flutter app to automatically switch between light and dark themes based on system settings, but also allow users to manually override the theme. Which approach correctly implements this behavior?

hard

A. Use darkTheme only and switch themes by restarting the app

B. Set themeMode: ThemeMode.system only and ignore user preferences

C. Use only theme and change colors manually in widgets

D. Use theme, darkTheme, and control themeMode with a user setting stored in state

Solution

1. Step 1: Understand system and user control

   To follow system theme and allow manual override, themeMode must be dynamic based on user choice.

2. Step 2: Implement themeMode with user state

   Store user preference in app state and set themeMode accordingly, while providing theme and darkTheme.

3. Final Answer:

   Use theme, darkTheme, and control themeMode with a user setting stored in state -> Option D

4. Quick Check:

   Dynamic themeMode enables system and user control [OK]

Hint: Control themeMode with user state for manual override [OK]

Common Mistakes:

• Ignoring user preferences with fixed themeMode
• Manually changing colors in widgets instead of themes
• Restarting app to apply theme changes