Custom fonts in Flutter - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

What is the output of this Flutter code snippet using a custom font?

Given the following Flutter widget, what font family will the displayed text use?

Flutter

Text('Hello Flutter', style: TextStyle(fontFamily: 'MyCustomFont'))

A The text uses the system default font.

B The text will not display because 'MyCustomFont' is not a valid font family name.

C The text uses the 'MyCustomFont' font family if properly registered.

D The text uses a random font from the device.

💡 Hint

Custom fonts must be registered in the pubspec.yaml file before use.

If the font family is registered correctly in pubspec.yaml, Flutter uses it for the text style.

📝 Syntax

intermediate

Which pubspec.yaml snippet correctly registers a custom font named 'MyCustomFont'?

Choose the correct way to declare a custom font in pubspec.yaml.

A

flutter:
  fonts:
    - family: MyCustomFont
      fonts:
        - asset: fonts/MyCustomFont.ttf

B

flutter:
  assets:
    - fonts/MyCustomFont.ttf

C

fonts:
  - family: MyCustomFont
    asset: fonts/MyCustomFont.ttf

D

flutter:
  fonts:
    - family: MyCustomFont
      asset: fonts/MyCustomFont.ttf

💡 Hint

Look for the correct indentation and keys under flutter.

The correct syntax uses 'fonts' under 'flutter', with 'family' and a list of 'fonts' assets.

❓ lifecycle

advanced

What happens if you add a new font asset but forget to run 'flutter pub get' before running the app?

Consider you added a new font file and updated pubspec.yaml but did not run 'flutter pub get'. What will happen when you run the app?

A The app will display the new font correctly without any issues.

B The app will use the default font instead of the new custom font.

C The app will crash immediately on startup.

D The app will show a compile-time error.

💡 Hint

Think about how Flutter updates dependencies and assets.

Without running 'flutter pub get', the new font asset is not registered, so Flutter falls back to the default font.

🔧 Debug

advanced

Why does this Flutter app fail to apply the custom font?

Given this pubspec.yaml snippet and Flutter code, why does the custom font not appear?

flutter:
  fonts:
    - family: MyFont
      fonts:
        - asset: fonts/MyFont-Regular.ttf

Text('Sample', style: TextStyle(fontFamily: 'MyCustomFont'))

A The Text widget does not support custom fonts.

B The font asset path is incorrect in pubspec.yaml.

C The font file is missing from the fonts folder.

D The font family name in TextStyle does not match the one declared in pubspec.yaml.

💡 Hint

Check the font family names carefully.

The TextStyle uses 'MyCustomFont' but the pubspec.yaml declares 'MyFont'. They must match exactly.

🧠 Conceptual

expert

How does Flutter handle font weight variations in custom fonts?

You have multiple font files for different weights (e.g., Regular, Bold) under the same family. How should you declare them in pubspec.yaml to enable Flutter to use them automatically?

A Declare each font file under the same family with the 'weight' property specifying the font weight.

B Declare only the Regular font file; Flutter will simulate other weights automatically.

C Flutter does not support multiple weights for custom fonts.

D Declare each font file under different family names for each weight.

💡 Hint

Look for how pubspec.yaml supports font weight declarations.

Flutter uses the 'weight' property to map font files to font weights under the same family.

Practice

1. What is the first step to use a custom font in a Flutter app?

easy

A. Add the font files to the assets folder and declare them in pubspec.yaml

B. Write the font name directly in the Text widget

C. Import a font package from pub.dev

D. Use the default system font without changes

Solution

1. Step 1: Add font files to assets

   You must first place your font files (like .ttf) inside an assets folder in your project.

2. Step 2: Declare fonts in pubspec.yaml

   Next, you declare these font files under the fonts section in pubspec.yaml so Flutter knows about them.

3. Final Answer:

   Add the font files to the assets folder and declare them in pubspec.yaml -> Option A

4. Quick Check:

   Custom fonts start with assets + pubspec.yaml declaration [OK]

Hint: Always start by adding font files and declaring in pubspec.yaml [OK]

Common Mistakes:

• Skipping pubspec.yaml declaration
• Trying to use font without adding files
• Using font name without quotes in TextStyle

2. Which of the following is the correct way to specify a custom font family in a Text widget's style?

easy

A. Text('Hello', style: TextStyle(fontStyle: 'MyFont'))

B. Text('Hello', style: TextStyle(font: 'MyFont'))

C. Text('Hello', style: TextStyle(fontName: 'MyFont'))

D. Text('Hello', style: TextStyle(fontFamily: 'MyFont'))

Solution

1. Step 1: Use fontFamily property in TextStyle

   The correct property to set a font family is fontFamily, not font, fontName, or fontStyle.

2. Step 2: Apply fontFamily in Text widget

   Use TextStyle(fontFamily: 'YourFontName') inside the style parameter of Text widget.

3. Final Answer:

   Text('Hello', style: TextStyle(fontFamily: 'MyFont')) -> Option D

4. Quick Check:

   fontFamily property sets custom font [OK]

Hint: Use fontFamily property inside TextStyle for custom fonts [OK]

Common Mistakes:

• Using font instead of fontFamily
• Confusing fontStyle with fontFamily
• Omitting quotes around font family name

3. Given this pubspec.yaml snippet:

fonts:
  - family: CoolFont
    fonts:
      - asset: assets/fonts/CoolFont-Regular.ttf
      - asset: assets/fonts/CoolFont-Bold.ttf
        weight: 700

What will this code display?

Text('Hi', style: TextStyle(fontFamily: 'CoolFont', fontWeight: FontWeight.bold))

medium

A. Text 'Hi' in CoolFont Bold style

B. Text 'Hi' in default font because fontWeight is ignored

C. Error because fontWeight 700 is invalid

D. Text 'Hi' in CoolFont Regular style ignoring bold

Solution

1. Step 1: Understand fontWeight mapping

   The pubspec.yaml declares two font assets: Regular (default weight) and Bold (weight 700).

2. Step 2: TextStyle uses fontWeight.bold

   Using fontWeight: FontWeight.bold matches weight 700, so Flutter uses the Bold font file.

3. Final Answer:

   Text 'Hi' in CoolFont Bold style -> Option A

4. Quick Check:

   fontWeight matches declared font weight for bold [OK]

Hint: Match fontWeight in TextStyle to declared font weights in pubspec.yaml [OK]

Common Mistakes:

• Ignoring fontWeight and expecting bold
• Assuming fontWeight 700 is invalid
• Not declaring font weights in pubspec.yaml

4. Why does this Flutter app fail to apply the custom font?

pubspec.yaml:
fonts:
  - family: FancyFont
    fonts:
      - asset: assets/fonts/FancyFont.ttf

Dart code:
Text('Hello', style: TextStyle(fontFamily: 'FancyFontt'))

medium

A. pubspec.yaml syntax error due to missing indentation

B. Font file is missing from assets folder

C. Font family name in TextStyle does not match pubspec.yaml

D. Text widget cannot use custom fonts

Solution

1. Step 1: Check fontFamily spelling in Dart code

   The Dart code uses 'FancyFontt' but pubspec.yaml declares 'FancyFont' (extra 't').

2. Step 2: Font family names must match exactly

   Font family names are case-sensitive and must match exactly between pubspec.yaml and Dart code.

3. Final Answer:

   Font family name in TextStyle does not match pubspec.yaml -> Option C

4. Quick Check:

   Font family names must match exactly [OK]

Hint: Check spelling of fontFamily matches pubspec.yaml exactly [OK]

Common Mistakes:

• Typos in font family names
• Forgetting to run flutter pub get after changes
• Incorrect indentation in pubspec.yaml

5. You want to use two different custom fonts in your Flutter app: 'Lobster' for titles and 'OpenSans' for body text. How should you organize your pubspec.yaml and Dart code to achieve this?

hard

A. Add both font files but use only one family name in pubspec.yaml

B. Declare both fonts under fonts in pubspec.yaml with different family names, then use fontFamily: 'Lobster' or 'OpenSans' in TextStyle accordingly

C. Declare only one font in pubspec.yaml and switch fontFamily names in Dart code

D. Use system fonts for titles and custom font for body text without declaring both

Solution

1. Step 1: Declare each font family separately in pubspec.yaml

   You must list each font family with its own name and font files under the fonts section.

2. Step 2: Use fontFamily property in Dart code for each Text widget

   Apply fontFamily: 'Lobster' for titles and fontFamily: 'OpenSans' for body text in TextStyle.

3. Final Answer:

   Declare both fonts under fonts in pubspec.yaml with different family names, then use fontFamily: 'Lobster' or 'OpenSans' in TextStyle accordingly -> Option B

4. Quick Check:

   Multiple fonts need separate declarations and usage [OK]

Hint: Declare each font family separately and use fontFamily accordingly [OK]

Common Mistakes:

• Declaring only one font family for multiple fonts
• Using wrong fontFamily names in Dart code
• Not adding all font files to assets