Manual day night switch button for settings activity.

res/drawable/ic_baseline_palette_24.xml

@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24"
+    android:tint="?attr/colorControlNormal">
+  <path
+      android:fillColor="@android:color/white"
+      android:pathData="M12,3c-4.97,0 -9,4.03 -9,9s4.03,9 9,9c0.83,0 1.5,-0.67 1.5,-1.5 0,-0.39 -0.15,-0.74 -0.39,-1.01 -0.23,-0.26 -0.38,-0.61 -0.38,-0.99 0,-0.83 0.67,-1.5 1.5,-1.5L16,16c2.76,0 5,-2.24 5,-5 0,-4.42 -4.03,-8 -9,-8zM6.5,12c-0.83,0 -1.5,-0.67 -1.5,-1.5S5.67,9 6.5,9 8,9.67 8,10.5 7.33,12 6.5,12zM9.5,8C8.67,8 8,7.33 8,6.5S8.67,5 9.5,5s1.5,0.67 1.5,1.5S10.33,8 9.5,8zM14.5,8c-0.83,0 -1.5,-0.67 -1.5,-1.5S13.67,5 14.5,5s1.5,0.67 1.5,1.5S15.33,8 14.5,8zM17.5,12c-0.83,0 -1.5,-0.67 -1.5,-1.5S16.67,9 17.5,9s1.5,0.67 1.5,1.5 -0.67,1.5 -1.5,1.5z"/>
+</vector>

res/layout/activity_settings.xml

@@ -111,17 +111,6 @@
                 android:layout_marginTop="@dimen/large_spacing"
                 android:background="?android:dividerHorizontal" />
 
-            <TextView
-                android:id="@+id/themeSwitchButton"
-                android:layout_width="match_parent"
-                android:layout_height="@dimen/setting_button_height"
-                android:background="@color/accent"
-                android:textColor="@color/text"
-                android:textSize="@dimen/medium_font_size"
-                android:textStyle="bold"
-                android:gravity="center"
-                android:text="Switch Theme" />
-
             <View
                 android:layout_width="match_parent"
                 android:layout_height="1px"

res/menu/settings_general.xml

@@ -3,6 +3,12 @@
     xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto">
 
+    <item
+        android:id="@+id/action_change_theme"
+        android:title=""
+        android:icon="@drawable/ic_baseline_palette_24"
+        app:showAsAction="always" />
+
     <item
         android:id="@+id/action_qr_code"
         android:title=""

src/org/thoughtcrime/securesms/loki/activities/SettingsActivity.kt

@@ -7,10 +7,7 @@ import android.content.Context
 import android.content.Intent
 import android.content.res.Configuration
 import android.net.Uri
-import android.os.AsyncTask
-import android.os.Bundle
-import android.os.Handler
-import android.os.Looper
+import android.os.*
 import android.view.ActionMode
 import android.view.Menu
 import android.view.MenuItem
@@ -99,15 +96,15 @@ class SettingsActivity : PassphraseRequiredActionBarActivity() {
         seedButton.setOnClickListener { showSeed() }
         clearAllDataButton.setOnClickListener { clearAllData() }
         versionTextView.text = String.format(getString(R.string.version_s), BuildConfig.VERSION_NAME)
-
-        themeSwitchButton.setOnClickListener {
-            setDarkTheme(!isDarkTheme())
-            recreate()
-        }
     }
 
     override fun onCreateOptionsMenu(menu: Menu): Boolean {
         menuInflater.inflate(R.menu.settings_general, menu)
+
+        // Day/night themes are only available since Android 10
+        menu.findItem(R.id.action_change_theme)
+                .setVisible(Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q)
+
         return true
     }
 
@@ -115,7 +112,19 @@ class SettingsActivity : PassphraseRequiredActionBarActivity() {
         return when (item.itemId) {
             R.id.action_qr_code -> {
                 showQRCode()
-                return true
+                true
+            }
+            R.id.action_change_theme -> {
+                // A temporary demo code that manually switches between day/night themes.
+                // The effect is reset after the app restart.
+                val currentUiMode = resources.configuration.uiMode and Configuration.UI_MODE_NIGHT_MASK
+                val nightMode: Int = when(currentUiMode) {
+                    Configuration.UI_MODE_NIGHT_YES -> AppCompatDelegate.MODE_NIGHT_NO
+                    else -> AppCompatDelegate.MODE_NIGHT_YES
+                }
+                AppCompatDelegate.setDefaultNightMode(nightMode)
+                recreate()
+                true
             }
             else -> super.onOptionsItemSelected(item)
         }
@@ -288,18 +297,6 @@ class SettingsActivity : PassphraseRequiredActionBarActivity() {
     }
     // endregion
 
-    //TODO Remove it.
-    private fun isDarkTheme(): Boolean {
-        val themeFlag = resources.configuration.uiMode and Configuration.UI_MODE_NIGHT_MASK
-        return themeFlag == Configuration.UI_MODE_NIGHT_YES;
-    }
-
-    //TODO Remove it.
-    private fun setDarkTheme(darkTheme: Boolean) {
-//        AppCompatDelegate.setDefaultNightMode(if (darkTheme) AppCompatDelegate.MODE_NIGHT_YES else AppCompatDelegate.MODE_NIGHT_NO )
-        AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_FOLLOW_SYSTEM)
-    }
-
     private inner class DisplayNameEditActionModeCallback: ActionMode.Callback {
 
         override fun onCreateActionMode(mode: ActionMode, menu: Menu): Boolean {