The AppCompat DayNight theme is a part of the AndroidX library, enabling your app to automatically switch between light and dark themes based on the user’s device settings or preferences. This feature helps in creating a more dynamic and user-friendly UI, providing better readability in various lighting conditions. In this blog, we will walk through the steps to implement a simple Android UI using the AppCompat DayNight theme.

Setting Up the AppCompat DayNight Theme

First, ensure you have the necessary dependencies in your build.gradle file.

Step 1: Add Dependencies

Open your build.gradle file and add the AndroidX AppCompat dependency:

dependencies {
    implementation 'androidx.appcompat:appcompat:1.3.1'
    implementation 'androidx.core:core-ktx:1.6.0'
}

Step 2: Define the Theme in styles.xml

Open your res/values/styles.xml file and define the AppCompat DayNight theme:

<resources>
    <!-- Base application theme -->
    <style name="AppTheme" parent="Theme.AppCompat.DayNight.DarkActionBar">
        <!-- Customize your theme here -->
        <item name="colorPrimary">@color/purple_500</item>
        <item name="colorPrimaryDark">@color/purple_700</item>
        <item name="colorAccent">@color/teal_200</item>
    </style>
</resources>

This setup ensures that your application uses the DayNight theme with a dark action bar by default.

Example: Creating a Simple UI with Toggle for DayNight Theme

Let’s create a simple UI that includes a toggle button to switch between day and night modes manually.

Step 3: Define the Layout

Create an XML layout file (activity_main.xml) with the following content:

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="16dp"
    android:gravity="center">

    <TextView
        android:id="@+id/greetingTextView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello, World!"
        android:textSize="24sp"
        android:layout_marginBottom="24dp"/>

    <Button
        android:id="@+id/toggleThemeButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Toggle Theme"/>

</LinearLayout>

Step 4: Initialize in Activity

In your MainActivity.java or MainActivity.kt file, initialize the views and add functionality to toggle the theme. Java

package com.example.daynighttheme;

import android.content.SharedPreferences;
import android.os.Bundle;
import android.widget.Button;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.app.AppCompatDelegate;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        TextView greetingTextView = findViewById(R.id.greetingTextView);
        Button toggleThemeButton = findViewById(R.id.toggleThemeButton);

        // Load the saved theme preference
        SharedPreferences sharedPreferences = getSharedPreferences("ThemePref", MODE_PRIVATE);
        boolean isNightMode = sharedPreferences.getBoolean("NightMode", false);

        if (isNightMode) {
            AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES);
        } else {
            AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_NO);
        }

        toggleThemeButton.setOnClickListener(v -> {
            boolean nightMode = (AppCompatDelegate.getDefaultNightMode() == AppCompatDelegate.MODE_NIGHT_YES);
            if (nightMode) {
                AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_NO);
                saveThemePreference(false);
            } else {
                AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES);
                saveThemePreference(true);
            }
        });
    }

    private void saveThemePreference(boolean isNightMode) {
        SharedPreferences.Editor editor = getSharedPreferences("ThemePref", MODE_PRIVATE).edit();
        editor.putBoolean("NightMode", isNightMode);
        editor.apply();
    }
}

Kotlin

package com.example.daynighttheme

import android.content.SharedPreferences
import android.os.Bundle
import android.widget.Button
import android.widget.TextView
import androidx.appcompat.app.AppCompatActivity
import androidx.appcompat.app.AppCompatDelegate

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val greetingTextView: TextView = findViewById(R.id.greetingTextView)
        val toggleThemeButton: Button = findViewById(R.id.toggleThemeButton)

        // Load the saved theme preference
        val sharedPreferences: SharedPreferences = getSharedPreferences("ThemePref", MODE_PRIVATE)
        val isNightMode = sharedPreferences.getBoolean("NightMode", false)

        if (isNightMode) {
            AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES)
        } else {
            AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_NO)
        }

        toggleThemeButton.setOnClickListener {
            val nightMode = AppCompatDelegate.getDefaultNightMode() == AppCompatDelegate.MODE_NIGHT_YES
            if (nightMode) {
                AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_NO)
                saveThemePreference(false)
            } else {
                AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES)
                saveThemePreference(true)
            }
        }
    }

    private fun saveThemePreference(isNightMode: Boolean) {
        val editor: SharedPreferences.Editor = getSharedPreferences("ThemePref", MODE_PRIVATE).edit()
        editor.putBoolean("NightMode", isNightMode)
        editor.apply()
    }
}

Conclusion

Using the AppCompat DayNight theme allows your app to dynamically adapt to the user’s preferred theme, enhancing the user experience in different lighting conditions. By following this guide, you can easily implement the DayNight theme in your Android application and provide a toggle for users to switch between day and night modes manually. This approach ensures your app remains modern and user-friendly. Happy coding!