Material 3 Theme, Colors और Dark Mode

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <color name="brand">#16A34A</color>
    <color name="brand_dark">#15803D</color>
    <color name="brand_light">#DCFCE7</color>
    <color name="accent">#F59E0B</color>
    <color name="star">#F59E0B</color>
    <color name="priority_high">#EF4444</color>
    <color name="priority_medium">#F59E0B</color>
    <color name="priority_low">#22C55E</color>
</resources>

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <!-- Material 3, light + dark (DayNight). We use our own Toolbar, so NoActionBar. -->
    <style name="Theme.StudentDiary" parent="Theme.Material3.DayNight.NoActionBar">
        <item name="colorPrimary">@color/brand</item>
        <item name="colorOnPrimary">@android:color/white</item>
        <item name="colorPrimaryContainer">@color/brand_light</item>
        <item name="colorOnPrimaryContainer">@color/brand_dark</item>
        <item name="colorSecondary">@color/accent</item>
        <item name="colorOnSecondary">@android:color/black</item>
    </style>

    <style name="StatCard" parent="Widget.Material3.CardView.Filled">
        <item name="cardCornerRadius">16dp</item>
    </style>
    <style name="StatBox">
        <item name="android:layout_width">match_parent</item>
        <item name="android:layout_height">wrap_content</item>
        <item name="android:orientation">vertical</item>
        <item name="android:gravity">center</item>
        <item name="android:padding">16dp</item>
    </style>
    <style name="StatNumber">
        <item name="android:layout_width">wrap_content</item>
        <item name="android:layout_height">wrap_content</item>
        <item name="android:textSize">28sp</item>
        <item name="android:textStyle">bold</item>
        <item name="android:textColor">?attr/colorPrimary</item>
        <item name="android:text">0</item>
    </style>
    <style name="StatLabel">
        <item name="android:layout_width">wrap_content</item>
        <item name="android:layout_height">wrap_content</item>
        <item name="android:textAppearance">?attr/textAppearanceLabelLarge</item>
    </style>
</resources>

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <!-- Dark mode: lighter green looks better on a dark background -->
    <style name="Theme.StudentDiary" parent="Theme.Material3.DayNight.NoActionBar">
        <item name="colorPrimary">#4ADE80</item>
        <item name="colorOnPrimary">#052E16</item>
        <item name="colorPrimaryContainer">#14532D</item>
        <item name="colorOnPrimaryContainer">#DCFCE7</item>
        <item name="colorSecondary">@color/accent</item>
        <item name="colorOnSecondary">@android:color/black</item>
    </style>
</resources>

<!-- ❌ fixed colour – stays white in dark mode -->
<LinearLayout android:background="#FFFFFF" />

<!-- ✅ theme attributes – change automatically -->
<LinearLayout android:background="?attr/colorSurface" />
<TextView android:textColor="?attr/colorOnSurface" />
<TextView android:textColor="?attr/colorPrimary" />
<TextView android:textAppearance="?attr/textAppearanceTitleMedium" />

package com.codingeasily.studentdiary.data

import android.content.Context
import androidx.appcompat.app.AppCompatDelegate
import androidx.core.content.edit

/** Small key-value settings saved with SharedPreferences. */
class SettingsStore(context: Context) {

    private val prefs = context.getSharedPreferences("settings", Context.MODE_PRIVATE)

    var userName: String
        get() = prefs.getString(KEY_NAME, "Student") ?: "Student"
        set(value) = prefs.edit { putString(KEY_NAME, value) }

    var darkMode: Boolean
        get() = prefs.getBoolean(KEY_DARK, false)
        set(value) = prefs.edit { putBoolean(KEY_DARK, value) }

    var remindersEnabled: Boolean
        get() = prefs.getBoolean(KEY_REMINDERS, true)
        set(value) = prefs.edit { putBoolean(KEY_REMINDERS, value) }

    fun applyTheme() {
        AppCompatDelegate.setDefaultNightMode(
            if (darkMode) AppCompatDelegate.MODE_NIGHT_YES else AppCompatDelegate.MODE_NIGHT_NO
        )
    }

    companion object {
        private const val KEY_NAME = "user_name"
        private const val KEY_DARK = "dark_mode"
        private const val KEY_REMINDERS = "reminders"
    }
}

// From Student Diary – SettingsFragment
binding.switchDark.isChecked = settings.darkMode
binding.switchDark.setOnCheckedChangeListener { _, checked ->
    settings.darkMode = checked
    settings.applyTheme()           // the activity is recreated with the new theme
}

// StudentDiaryApp.onCreate() – apply the saved choice when the app starts
SettingsStore(this).applyTheme()

// app module: Application class
class StudentDiaryApp : Application() {
    override fun onCreate() {
        super.onCreate()
        DynamicColors.applyToActivitiesIfAvailable(this)   // wallpaper colours on Android 12+
    }
}