Material Theme customization in Android Kotlin

Introduction

Material Theme customization lets you change colors, fonts, and shapes in your app. This helps your app look unique and match your brand.

You want your app to have your brand colors instead of default colors.

You want to change the font style to make text easier to read or more fun.

You want buttons and cards to have rounded corners or different shapes.

You want to create a dark mode with different colors.

You want consistent style across all screens in your app.

Syntax

Android Kotlin

val colors = lightColorScheme(
    primary = Color(0xFF6200EE),
    secondary = Color(0xFF03DAC6),
    background = Color(0xFFFFFFFF)
)

MaterialTheme(
    colorScheme = colors,
    typography = Typography(),
    shapes = Shapes(),
    content = { /* Your UI here */ }
)

Use lightColorScheme or darkColorScheme to define colors.

Pass your custom colors, typography, and shapes to MaterialTheme.

Examples

This example changes the main colors of the app.

Android Kotlin

val customColors = lightColorScheme(
    primary = Color(0xFFBB86FC),
    secondary = Color(0xFF03DAC5),
    background = Color(0xFFF0EAE2)
)

MaterialTheme(colorScheme = customColors) {
    Text("Hello with custom colors")
}

This example changes the shape of buttons and cards to have rounded corners.

Android Kotlin

val customShapes = Shapes(
    small = RoundedCornerShape(8.dp),
    medium = RoundedCornerShape(16.dp),
    large = RoundedCornerShape(0.dp)
)

MaterialTheme(shapes = customShapes) {
    Button(onClick = {}) {
        Text("Rounded Button")
    }
}

Sample App

This app uses a custom color scheme and shapes. The background is light gray, the title text is purple, and the button has rounded corners.

Android Kotlin

import androidx.compose.foundation.layout.*
import androidx.compose.material3.*
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.unit.dp

@Composable
fun CustomThemeApp() {
    val customColors = lightColorScheme(
        primary = Color(0xFF6200EE),
        secondary = Color(0xFF03DAC6),
        background = Color(0xFFF0F0F0)
    )

    val customShapes = Shapes(
        small = RoundedCornerShape(12.dp),
        medium = RoundedCornerShape(24.dp),
        large = RoundedCornerShape(0.dp)
    )

    MaterialTheme(
        colorScheme = customColors,
        shapes = customShapes
    ) {
        Surface(modifier = Modifier.fillMaxSize(), color = MaterialTheme.colorScheme.background) {
            Column(
                modifier = Modifier.padding(16.dp),
                verticalArrangement = Arrangement.spacedBy(12.dp)
            ) {
                Text("Welcome to Custom Theme!", style = MaterialTheme.typography.headlineMedium, color = MaterialTheme.colorScheme.primary)
                Button(onClick = {}, shape = MaterialTheme.shapes.medium) {
                    Text("Click Me")
                }
            }
        }
    }
}

Important Notes

Always define colors for both light and dark themes for better user experience.

Use MaterialTheme to wrap your UI so all components use your custom styles.

Shapes affect buttons, cards, and other surfaces. Adjust them to match your design.

Summary

Material Theme customization changes colors, fonts, and shapes in your app.

Use colorScheme, typography, and shapes to customize.

Wrap your UI in MaterialTheme to apply your custom styles everywhere.

Practice

1. What is the main purpose of customizing the MaterialTheme in an Android app?

easy

A. To add new activities to the app

B. To change the app's colors, fonts, and shapes globally

C. To manage app permissions

D. To handle network requests

Solution

1. Step 1: Understand MaterialTheme role

   The MaterialTheme controls the look and feel of the app by setting colors, typography, and shapes.

2. Step 2: Identify customization purpose

   Customizing MaterialTheme changes these visual styles globally for consistency.

3. Final Answer:

   To change the app's colors, fonts, and shapes globally -> Option B

4. Quick Check:

   MaterialTheme customization = change colors, fonts, shapes [OK]

Hint: MaterialTheme controls app-wide style settings [OK]

Common Mistakes:

• Confusing theme customization with adding app features
• Thinking it manages app permissions
• Assuming it handles network or data logic

2. Which of the following is the correct way to apply a custom color scheme in MaterialTheme in Kotlin?

easy

A. MaterialTheme(colorScheme = myColors) { /* UI content */ }

B. MaterialTheme(colors = myColors) { /* UI content */ }

C. MaterialTheme(setColors = myColors) { /* UI content */ }

D. MaterialTheme(applyColors = myColors) { /* UI content */ }

Solution

1. Step 1: Recall MaterialTheme parameters

   The correct parameter for colors in MaterialTheme is colorScheme.

2. Step 2: Match correct syntax

   MaterialTheme(colorScheme = myColors) { /* UI content */ } uses colorScheme = myColors, which is the correct syntax in Kotlin.

3. Final Answer:

   MaterialTheme(colorScheme = myColors) { /* UI content */ } -> Option A

4. Quick Check:

   Use colorScheme parameter for colors [OK]

Hint: Use colorScheme, not colors, in MaterialTheme [OK]

Common Mistakes:

• Using 'colors' instead of 'colorScheme'
• Using non-existent parameters like 'setColors' or 'applyColors'
• Forgetting to wrap UI content inside the theme block

3. Given the code snippet below, what color will the Text component display if primary in colorScheme is set to Color.Red?

MaterialTheme(
  colorScheme = ColorScheme(
    primary = Color.Red,
    secondary = Color.Blue
  )
) {
  Text("Hello", color = MaterialTheme.colorScheme.primary)
}

medium

A. Blue

B. Green

C. Red

D. Default text color

Solution

1. Step 1: Identify colorScheme primary value

   The primary color in colorScheme is set to Color.Red.

2. Step 2: Check Text color usage

   The Text color uses MaterialTheme.colorScheme.primary, so it will be Color.Red.

3. Final Answer:

   Red -> Option C

4. Quick Check:

   Text color = primary color = Red [OK]

Hint: Text color uses primary from colorScheme [OK]

Common Mistakes:

• Confusing primary with secondary color
• Assuming default color instead of theme color
• Mixing up color names

4. What is wrong with the following Kotlin code that tries to customize the MaterialTheme's typography?

MaterialTheme(
  typography = Typography(
    bodyLarge = TextStyle(fontSize = 20)
  )
) {
  Text("Welcome")
}

medium

A. TextStyle requires a unit for fontSize, like sp or dp

B. Typography cannot be customized in MaterialTheme

C. Text component must specify typography explicitly

D. MaterialTheme must not have a typography parameter

Solution

1. Step 1: Check TextStyle fontSize usage

   The fontSize must include a unit like 20.sp, not just 20.

2. Step 2: Identify correct syntax

   Without the unit, the code will cause a type error because fontSize expects a TextUnit.

3. Final Answer:

   TextStyle requires a unit for fontSize, like sp or dp -> Option A

4. Quick Check:

   fontSize needs unit like sp [OK]

Hint: Always add .sp for fontSize values [OK]

Common Mistakes:

• Omitting units for fontSize
• Thinking typography can't be customized
• Expecting Text to need explicit typography parameter

5. You want to create a custom shape for buttons in your app using MaterialTheme. Which approach correctly applies a rounded corner shape of 16.dp to all buttons?

hard

A. MaterialTheme(shapes = Shapes(extraLarge = RoundedCornerShape(16.dp))) { Button(...) }

B. MaterialTheme(shapes = Shapes(small = RoundedCornerShape(16.dp))) { Button(...) }

C. MaterialTheme(shapes = Shapes(large = RoundedCornerShape(16.dp))) { Button(...) }

D. MaterialTheme(shapes = Shapes(medium = RoundedCornerShape(16.dp))) { Button(...) }

Solution

1. Step 1: Understand shape categories in MaterialTheme

   MaterialTheme defines shapes as small, medium, and large. Buttons use the medium shape by default.

2. Step 2: Apply rounded corners to medium shape

   Setting medium = RoundedCornerShape(16.dp) customizes button corners.

3. Final Answer:

   MaterialTheme(shapes = Shapes(medium = RoundedCornerShape(16.dp))) { Button(...) } -> Option D

4. Quick Check:

   Buttons use medium shape slot [OK]

Hint: Buttons use medium shape in MaterialTheme [OK]

Common Mistakes:

• Changing small or large shapes instead of medium
• Using non-existent shape categories like extraLarge
• Forgetting to wrap Button inside MaterialTheme