restore flashlight/stroboscope state on device rotation

app/src/main/kotlin/com/simplemobiletools/flashlight/activities/MainActivity.kt

@@ -25,9 +25,12 @@ import kotlinx.android.synthetic.main.activity_main.*
 class MainActivity : SimpleActivity() {
     private val MAX_STROBO_DELAY = 2000
     private val MIN_STROBO_DELAY = 30
+    private val FLASHLIGHT_STATE = "flashlight_state"
+    private val STROBOSCOPE_STATE = "stroboscope_state"
 
     private var mBus: Bus? = null
     private var mCameraImpl: MyCameraImpl? = null
+    private var mIsFlashlightOn = false
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
@@ -41,7 +44,7 @@ class MainActivity : SimpleActivity() {
             startActivity(Intent(applicationContext, BrightDisplayActivity::class.java))
         }
 
-        toggle_btn.setOnClickListener {
+        flashlight_btn.setOnClickListener {
             mCameraImpl!!.toggleFlashlight()
         }
 
@@ -100,6 +103,25 @@ class MainActivity : SimpleActivity() {
         return true
     }
 
+    override fun onSaveInstanceState(outState: Bundle) {
+        outState.putBoolean(FLASHLIGHT_STATE, mIsFlashlightOn)
+        outState.putBoolean(STROBOSCOPE_STATE, stroboscope_bar.isVisible())
+        super.onSaveInstanceState(outState)
+    }
+
+    override fun onRestoreInstanceState(savedInstanceState: Bundle) {
+        super.onRestoreInstanceState(savedInstanceState)
+        val isFlashlightOn = savedInstanceState.getBoolean(FLASHLIGHT_STATE, false)
+        if (isFlashlightOn) {
+            mCameraImpl!!.toggleFlashlight()
+        }
+
+        val isStroboscopeOn = savedInstanceState.getBoolean(STROBOSCOPE_STATE, false)
+        if (isStroboscopeOn) {
+            toggleStroboscope()
+        }
+    }
+
     private fun launchSettings() {
         startActivity(Intent(applicationContext, SettingsActivity::class.java))
     }
@@ -185,16 +207,18 @@ class MainActivity : SimpleActivity() {
     }
 
     private fun enableFlashlight() {
-        changeIconColor(getAdjustedPrimaryColor(), toggle_btn)
+        changeIconColor(getAdjustedPrimaryColor(), flashlight_btn)
         window.addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON)
+        mIsFlashlightOn = true
 
         changeIconColor(config.backgroundColor.getContrastColor(), stroboscope_btn)
         stroboscope_bar.beInvisible()
     }
 
     private fun disableFlashlight() {
-        changeIconColor(config.backgroundColor.getContrastColor(), toggle_btn)
+        changeIconColor(config.backgroundColor.getContrastColor(), flashlight_btn)
         window.clearFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON)
+        mIsFlashlightOn = false
     }
 
     private fun changeIconColor(color: Int, imageView: ImageView?) {

app/src/main/kotlin/com/simplemobiletools/flashlight/helpers/MyWidgetProvider.kt

@@ -31,8 +31,8 @@ class MyWidgetProvider : AppWidgetProvider() {
             val views = RemoteViews(context.packageName, R.layout.widget)
 
             val pendingIntent = PendingIntent.getBroadcast(context, it, intent, 0)
-            views.setOnClickPendingIntent(R.id.toggle_btn, pendingIntent)
+            views.setOnClickPendingIntent(R.id.flashlight_btn, pendingIntent)
-            views.setImageViewBitmap(R.id.toggle_btn, bmp)
+            views.setImageViewBitmap(R.id.flashlight_btn, bmp)
             appWidgetManager.updateAppWidget(it, views)
         }
     }
@@ -62,7 +62,7 @@ class MyWidgetProvider : AppWidgetProvider() {
             val appWidgetManager = AppWidgetManager.getInstance(context)
             appWidgetManager.getAppWidgetIds(getComponentName(context)).forEach {
                 val views = RemoteViews(context.packageName, R.layout.widget)
-                views.setImageViewBitmap(R.id.toggle_btn, bmp)
+                views.setImageViewBitmap(R.id.flashlight_btn, bmp)
                 appWidgetManager.updateAppWidget(it, views)
             }
         }

app/src/main/res/layout/activity_main.xml

@@ -13,7 +13,7 @@
         android:layout_height="wrap_content">
 
         <ImageView
-            android:id="@+id/toggle_btn"
+            android:id="@+id/flashlight_btn"
             android:layout_width="@dimen/main_button_size"
             android:layout_height="@dimen/main_button_size"
             android:layout_marginBottom="@dimen/activity_margin"
@@ -37,7 +37,7 @@
             app:layout_constraintEnd_toEndOf="parent"
             app:layout_constraintHorizontal_bias="0.5"
             app:layout_constraintStart_toStartOf="parent"
-            app:layout_constraintTop_toBottomOf="@+id/toggle_btn"/>
+            app:layout_constraintTop_toBottomOf="@+id/flashlight_btn"/>
 
         <ImageView
             android:id="@+id/stroboscope_btn"

app/src/main/res/layout/widget.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <ImageView
     xmlns:android="http://schemas.android.com/apk/res/android"
-    android:id="@+id/toggle_btn"
+    android:id="@+id/flashlight_btn"
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
     android:layout_margin="5dp"/>