Added Preferences class

app/src/main/kotlin/com/tutpro/baresip/Preferences.kt

@@ -0,0 +1,17 @@
+package com.tutpro.baresip
+
+import android.content.Context
+import androidx.preference.PreferenceManager
+
+class Preferences(context: Context) {
+
+    companion object {
+        private const val DISPLAY_THEME = "com.tutpro.baresip.DISPLAY_THEME"
+    }
+
+    private val preferences = PreferenceManager.getDefaultSharedPreferences(context)
+
+    var displayTheme = preferences.getInt(DISPLAY_THEME, -1)
+        set(value) = preferences.edit().putInt(DISPLAY_THEME, value).apply()
+
+}