Set Background Color for All Activities via theme.xml in Android Studio

When developing an Android application, maintaining a consistent UI is crucial for a better user experience. Instead of setting the background color for each activity manually, you can define it globally using thetheme.xml file. This approach ensures uniformity and saves development time.

Step 1: Open theme.xml

The theme.xml file is where you define global styles for your app. To find it:

1. Open Android Studio.

2. Navigate to res > values > themes.xml (or styles.xml in older versions).

3. Open the themes.xml file.

Step 2: Modify theme.xml

To change the background color for all activities, add the android:windowBackground attribute inside the <style> tag.

Example Code:

<!-- Apps background color. -->
<item name="android:windowBackground">@color/background_color</item>

Step 3: Apply the Theme to Your App

Ensure that the updated theme is applied in the AndroidManifest.xml file.

1. Open AndroidManifest.xml.

2. Locate the <application> tag.

3. Set the android:theme attribute to your custom theme.

Example:

<application
android:theme="@style/Theme.MyApp">
</application>

Step 4: Run Your App

Now, when you run your app, all activities will have the defined background color without manually setting it for each one.

Bonus: Setting a Different Background for Dark Mode

If your app supports dark mode, define a separate background color for theme.xml (night).

Example for Dark Mode:

<resources>
<style name="Theme.MyApp" parent="Theme.MaterialComponents.Dark.NoActionBar">
<item name="android:windowBackground">#212121</item>
</style>
</resources>

Conclusion

Setting the background color for all activities using theme.xml simplifies app design, ensures consistency, and saves time. By following this method, you can easily manage light and dark mode themes in your Android app.

Now that you know how to set a global background color, experiment with different colors and enhance your app's UI!