How to change text size in Android app development : Kotlin & Flutter

Text size plays a crucial role in user experience, especially on mobile devices. This tutorial will guide you on implementing text size adjustments in both Android (using Kotlin) and Flutter applications.

Understanding Text Size Options 🔗

• Default System Settings: Both Android and iOS allow users to adjust the overall font size in their system settings. Your app should respect these settings by default.
• In-App Adjustments: You can provide additional control within your app for users to further personalize the text size.

I. Android (Kotlin) 🔗

There are two main approaches to modify text size in an Android app written with Kotlin:

1. Styles and Themes 🔗

This approach is ideal for consistent text size adjustments across your app.

• Create Styles: Define styles in your styles.xml file with desired text size settings using the android:textSize attribute. You can create multiple styles for different text sizes (small, medium, large).

<style name="SmallText">
    <item name="android:textSize">14sp</item>
</style>

<style name="MediumText">
    <item name="android:textSize">16sp</item>
</style>

<style name="LargeText">
    <item name="android:textSize">18sp</item>
</style>

• Apply Styles: Set the style for your TextViews or other text elements in your layout XML files using the style attribute.

<TextView
    android:id="@+id/myTextView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="This is text"
    android:style="@style/MediumText" />

• Theming: Create a theme that includes your custom styles and apply it to your entire activity or specific views.

2. Programmatic Changes 🔗

This approach allows for dynamic text size adjustments based on user interaction or preferences.

• Get Text Size Preference: Implement a mechanism to retrieve the desired text size from user preferences (SharedPreferences).
• Set Text Size Programmatically: Use the setTextSize method on your text element, passing the retrieved value in sp (scaled pixels).

val textView = findViewById<TextView>(R.id.myTextView)
val preferredTextSize = getFontSizeFromPreferences()
textView.setTextSize(TypedValue.COMPLEX_UNIT_SP, preferredTextSize.toFloat())

II. Flutter 🔗

Flutter offers a more centralized approach to text size adjustments.

• MediaQuery: Use the MediaQuery class to access the user’s preferred text scale factor set in system settings.

double textScaleFactor = MediaQuery.of(context).textScaleFactor;

• Wrap Widgets: Wrap your text widgets with MediaQuery to automatically scale the text size based on the system setting.

MediaQuery(
  data: MediaQuery.of(context).copyWith(
    textScaleFactor: 1.2, // You can also set a custom factor here
  ),
  child: Text(
    'This is text',
    style: TextStyle(fontSize: 16.0),
  ),
)

Additional Considerations 🔗

• Accessibility: Ensure your app remains accessible with various text size adjustments. Consider using relative units (sp) instead of absolute units (dp) for better scaling.
• Testing: Thoroughly test your app on different devices and screen sizes to ensure proper text rendering across various text size configurations.

By following these approaches, you can effectively implement text size adjustments in your Android (Kotlin) and Flutter mobile applications, enhancing user experience and accessibility.

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