SharedPreferences और DataStore

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

// write
prefs.edit {                                  // androidx.core.content.edit
    putString("user_name", "Riya")
    putBoolean("dark_mode", true)
    putInt("launch_count", 5)
}

// read (always give a default)
val name = prefs.getString("user_name", "Student")
val dark = prefs.getBoolean("dark_mode", false)
val count = prefs.getInt("launch_count", 0)

// remove / clear
prefs.edit { remove("user_name") }
prefs.edit { clear() }

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"
    }
}

// Student Diary – SettingsFragment
settings = SettingsStore(requireContext())
binding.etName.setText(settings.userName)
binding.btnSaveName.setOnClickListener { settings.userName = binding.etName.text.toString() }

// MainActivity.onResume – show it in the drawer header
header.tvUserName.text = getString(R.string.hello_user, SettingsStore(this).userName)

class SplashActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        val prefs = getSharedPreferences("app", MODE_PRIVATE)
        val seen = prefs.getBoolean("onboarding_done", false)
        startActivity(Intent(this, if (seen) MainActivity::class.java else OnboardingActivity::class.java))
        finish()
    }
}

// OnboardingActivity – when the user taps "Get started"
getSharedPreferences("app", MODE_PRIVATE).edit { putBoolean("onboarding_done", true) }

// libs.versions.toml
datastore = "1.1.1"
androidx-datastore-preferences = { group = "androidx.datastore", name = "datastore-preferences", version.ref = "datastore" }

// app/build.gradle.kts
implementation(libs.androidx.datastore.preferences)

// One DataStore per file – declared at top level of a Kotlin file
val Context.dataStore by preferencesDataStore(name = "settings")

object Keys {
    val USER_NAME = stringPreferencesKey("user_name")
    val DARK_MODE = booleanPreferencesKey("dark_mode")
}

class SettingsRepository(private val context: Context) {
    // read as a Flow – the UI updates whenever the value changes
    val userName: Flow<String> = context.dataStore.data.map { it[Keys.USER_NAME] ?: "Student" }

    suspend fun setUserName(name: String) {
        context.dataStore.edit { it[Keys.USER_NAME] = name }
    }
}

// Fragment
viewLifecycleOwner.lifecycleScope.launch {
    repo.userName.collect { binding.tvHello.text = "Hello, $it" }
}
binding.btnSave.setOnClickListener {
    viewLifecycleOwner.lifecycleScope.launch { repo.setUserName(binding.etName.text.toString()) }
}