add a function for updating the window background

library/src/main/kotlin/com/simplemobiletools/commons/activities/BaseSimpleActivity.kt

@@ -20,6 +20,7 @@ open class BaseSimpleActivity : AppCompatActivity() {
 
     override fun onCreate(savedInstanceState: Bundle?) {
         baseConfig = BaseConfig.newInstance(applicationContext)
+        updateBackgroundColor()
         super.onCreate(savedInstanceState)
     }
 
@@ -33,6 +34,10 @@ open class BaseSimpleActivity : AppCompatActivity() {
         }
     }
 
+    fun updateBackgroundColor() {
+        window.decorView.setBackgroundColor(baseConfig.backgroundColor)
+    }
+
     override fun onActivityResult(requestCode: Int, resultCode: Int, resultData: Intent?) {
         super.onActivityResult(requestCode, resultCode, resultData)
         if (requestCode == OPEN_DOCUMENT_TREE && resultCode == Activity.RESULT_OK && resultData != null) {

library/src/main/kotlin/com/simplemobiletools/commons/activities/CustomizationActivity.kt

@@ -44,6 +44,7 @@ class CustomizationActivity : BaseSimpleActivity() {
             override fun onOk(dialog: AmbilWarnaDialog, color: Int) {
                 baseConfig.backgroundColor = color
                 setupColors()
+                updateBackgroundColor()
             }
         }).show()
     }