Error display patterns in Flutter - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to show a simple error message using Flutter's Text widget.

Flutter

return Scaffold(
  body: Center(
    child: Text([1]),
  ),
);

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

AshowError()

B"Error occurred!"

CText('Error occurred!')

DError occurred!

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting quotes around the string

Passing a function instead of a string

The Text widget requires a string inside quotes to display text. So, "Error occurred!" is correct.

2fill in blank

medium

Complete the code to display an error icon before the error message.

Flutter

return Scaffold(
  body: Center(
    child: Row(
      mainAxisSize: MainAxisSize.min,
      children: [
        Icon([1]),
        SizedBox(width: 8),
        Text('Error loading data'),
      ],
    ),
  ),
);

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

AIcons.home

BIcons.check

CIcons.error

DIcons.info

Attempts:

3 left

💡 Hint

Common Mistakes

Using unrelated icons like check or home

Forgetting to import material icons

Icons.error shows a standard error icon, which fits the error message context.

3fill in blank

hard

Fix the error in the code to show a red colored error message.

Flutter

return Scaffold(
  body: Center(
    child: Text(
      'Failed to load',
      style: TextStyle(color: [1]),
    ),
  ),
);

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

AColors.red

Bred

C"red"

DColor.red

Attempts:

3 left

💡 Hint

Common Mistakes

Using string 'red' instead of Colors.red

Using Color.red which does not exist

Colors.red is the correct way to specify red color in Flutter's Color class.

4fill in blank

hard

Fill both blanks to create a reusable error widget with a red icon and message.

Flutter

Widget errorDisplay() {
  return Row(
    children: [
      Icon([1], color: Colors.red),
      SizedBox(width: 5),
      Text([2], style: TextStyle(color: Colors.red)),
    ],
  );
}

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

AIcons.error

B"An error occurred"

CIcons.check_circle

D"Success!"

Attempts:

3 left

💡 Hint

Common Mistakes

Using success icons or messages

Mismatched colors or icons

Icons.error and a red error message string create a consistent error display.

5fill in blank

hard

Fill all three blanks to create an error alert with icon, message, and a retry button.

Flutter

return Column(
  mainAxisAlignment: MainAxisAlignment.center,
  children: [
    Icon([1], size: 48, color: Colors.red),
    Text([2], style: TextStyle(color: Colors.red, fontSize: 18)),
    ElevatedButton(
      onPressed: [3],
      child: Text('Retry'),
    ),
  ],
);

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

AIcons.error_outline

B"Unable to fetch data"

C() => fetchData()

D() => print('Retry clicked')

Attempts:

3 left

💡 Hint

Common Mistakes

Using success icons or messages

Leaving onPressed null or incorrect

Using wrong icon size or color

Icons.error_outline shows an error icon, the message explains the error, and the button triggers a retry action (here a print statement for demo).

Practice

1. What is the best way to show an error message for a text input field in Flutter?

easy

A. Show a SnackBar without any text input changes

B. Use the errorText property in InputDecoration of TextField

C. Use a Container with red background below the field

D. Change the TextField font size to smaller

Solution

1. Step 1: Understand Flutter form error display

   Flutter provides errorText in InputDecoration to show inline error messages below text fields.

2. Step 2: Compare options for error display

   Using errorText is the standard and clear way. SnackBar is for brief messages, Container with red background is not standard, and font size change does not convey error.

3. Final Answer:

   Use the errorText property in InputDecoration of TextField -> Option B

4. Quick Check:

   Inline error message = errorText [OK]

Hint: Use errorText for inline field errors [OK]

Common Mistakes:

• Using SnackBar for field errors
• Changing font size to indicate error
• Adding unrelated colored containers

2. Which Flutter widget is used to show a brief message at the bottom of the screen for errors?

easy

A. SnackBar

B. AlertDialog

C. Tooltip

D. Dialog

Solution

1. Step 1: Identify widget for brief messages

   SnackBar is designed to show short messages at the bottom of the screen temporarily.

2. Step 2: Differentiate from other widgets

   AlertDialog and Dialog are modal dialogs requiring user action. Tooltip shows hints on hover or long press, not error messages.

3. Final Answer:

   SnackBar -> Option A

4. Quick Check:

   Brief bottom message = SnackBar [OK]

Hint: SnackBar shows quick messages at screen bottom [OK]

Common Mistakes:

• Confusing AlertDialog with SnackBar
• Using Tooltip for error messages
• Using Dialog without user action

3. What will happen if you run this Flutter code snippet?

ScaffoldMessenger.of(context).showSnackBar(
  SnackBar(content: Text('Error occurred!'))
);

medium

A. A red error dialog appears in the center

B. App crashes due to missing AlertDialog

C. A brief message 'Error occurred!' appears at the bottom

D. Nothing happens because SnackBar needs a Scaffold

Solution

1. Step 1: Understand SnackBar usage with ScaffoldMessenger

   Using ScaffoldMessenger.of(context).showSnackBar() correctly shows a SnackBar message at the bottom of the screen.

2. Step 2: Analyze the code behavior

   The SnackBar with text 'Error occurred!' will appear briefly at the bottom. It does not show a dialog or crash.

3. Final Answer:

   A brief message 'Error occurred!' appears at the bottom -> Option C

4. Quick Check:

   ScaffoldMessenger.showSnackBar = brief message at bottom [OK]

Hint: SnackBar shows text at bottom, not dialog [OK]

Common Mistakes:

• Thinking SnackBar is a dialog
• Assuming SnackBar needs AlertDialog
• Believing SnackBar causes crash

4. You want to show an error alert dialog in Flutter but your code throws an exception. Which is the likely cause?

showDialog(
  context: context,
  builder: (context) => AlertDialog(
    title: Text('Error'),
    content: Text('Something went wrong'),
  ),
);

medium

A. Using showDialog without a valid context

B. Not wrapping AlertDialog in a MaterialApp

C. Missing Navigator.pop(context) to close dialog

D. AlertDialog requires a SnackBar inside

Solution

1. Step 1: Check context usage in showDialog

   showDialog requires a valid BuildContext from a widget tree that includes a MaterialApp or WidgetsApp.

2. Step 2: Identify common error cause

   Passing an invalid or null context causes exceptions. Missing Navigator.pop only affects closing, not showing. AlertDialog does not require SnackBar.

3. Final Answer:

   Using showDialog without a valid context -> Option A

4. Quick Check:

   Valid context needed for showDialog [OK]

Hint: Always pass valid context to showDialog [OK]

Common Mistakes:

• Forgetting to provide valid context
• Confusing SnackBar with AlertDialog requirements
• Not handling dialog dismissal

5. You want to display multiple form field errors and a general error alert in Flutter. Which approach correctly combines inline errors and an alert dialog?

hard

A. Change field colors to red and show no dialogs

B. Show all errors only in a SnackBar at the bottom

C. Use AlertDialog for each field error and ignore inline errors

D. Use errorText for each field and show an AlertDialog for general errors

Solution

1. Step 1: Understand error display roles

   Inline errors for fields use errorText to show specific issues. General errors affecting the whole form use AlertDialog to grab attention.

2. Step 2: Evaluate options for combined error display

   Use errorText for each field and show an AlertDialog for general errors correctly uses inline errors for fields and an alert dialog for general errors. SnackBar is brief and not suitable for multiple detailed errors. Using AlertDialog for each field is disruptive. Changing colors alone is unclear.

3. Final Answer:

   Use errorText for each field and show an AlertDialog for general errors -> Option D

4. Quick Check:

   Inline errors + alert dialog [OK]

Hint: Combine errorText for fields and AlertDialog for general errors [OK]

Common Mistakes:

• Showing all errors only in SnackBar
• Using AlertDialog for each field error
• Ignoring inline error messages