[JAVA] [Android] How to deal with dark themes

Introduction

This section describes how to support the dark theme (dark mode) app, which is fully supported from Android 10.

Resource creation

res/values/styles.xml First of all, update styles.xml, which is also used for normal theme customization, and define the color you want to switch when dark mode is ON / OFF.

<resources>
    <style name="AppTheme" parent="Theme.MaterialComponents.Light.DarkActionBar">
        <!-- Customize your theme here. -->
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>
        <item name="android:colorBackground">@color/colorBackground</item>
        <item name="android:textColor">@color/textColor</item>
        <item name="android:textColorPrimary">@color/textColorPrimary</item>
        <item name="android:textColorSecondary">@color/textColorSecondary</item>
    </style>
</resources>

Creating colors.xml

Describe the color definition referenced when dark mode is enabled in the system settings in res / values-night / colors.xml, and the normal color in res / values / colors.xml.

Example) res / values-night / colors.xml

<resources>
    <color name="colorPrimary">#212121</color>
    <color name="colorPrimaryDark">#212121</color>
    <color name="colorAccent">#80cbc4</color>
    <color name="colorTransparent">#00000000</color>
    <color name="textColor">#FFFFFF</color>
    <color name="textColorPrimary">#FFFFFF</color>
    <color name="textColorSecondary">#808080</color>
    <color name="colorBackground">#313131</color>
    <color name="colorCardBackground">@color/colorPrimary</color>
    <color name="colorBackgroundBottomAppBar">#353535</color>
</resources>

If you support up to this point, the display will switch according to the system settings without writing any code.

If you want to switch dynamically with the settings in the app

Use AppCompatDelegate.setDefaultNightMode to apply to the entire app.

Always displayed with a dark theme

AppCompatDelegate.setDefaultNightMode(MODE_NIGHT_YES); //Applies to the entire app
AppCompatDelegate.setLocalNightMode(MODE_NIGHT_YES);   //Applies only to specific activities

Always dark theme OFF (normal display)

AppCompatDelegate.setDefaultNightMode(MODE_NIGHT_NO); //Applies to the entire app
AppCompatDelegate.setLocalNightMode(MODE_NIGHT_NO);  //Applies only to specific activities

Linked to system settings (this is the default unless otherwise specified)

AppCompatDelegate.setDefaultNightMode(MODE_NIGHT_FOLLOW_SYSTEM); //Applies to the entire app
AppCompatDelegate.setLocalNightMode(MODE_NIGHT_FOLLOW_SYSTEM);   //Applies only to specific activities