change the way we calculate the navigation bar height

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

@@ -22,6 +22,7 @@ import com.bumptech.glide.load.engine.DiskCacheStrategy
 import com.simplemobiletools.camera.*
 import com.simplemobiletools.camera.Preview.PreviewListener
 import com.simplemobiletools.camera.extensions.config
+import com.simplemobiletools.camera.extensions.navBarHeight
 import com.simplemobiletools.camera.views.FocusRectView
 import com.simplemobiletools.commons.extensions.*
 import com.simplemobiletools.commons.models.Release
@@ -124,10 +125,7 @@ class MainActivity : SimpleActivity(), SensorEventListener, PreviewListener, Pho
         setContentView(R.layout.activity_main)
         initButtons()
 
-        if (mRes.hasNavBar() && Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
-            val lp = btn_holder.layoutParams as RelativeLayout.LayoutParams
-            lp.setMargins(0, 0, 0, lp.bottomMargin + mRes.getNavBarHeight())
-        }
+        (btn_holder.layoutParams as RelativeLayout.LayoutParams).setMargins(0, 0, 0, navBarHeight)
 
         mCurrCameraId = config.lastUsedCamera
         mPreview = Preview(this, camera_view, this)

app/src/main/kotlin/com/simplemobiletools/camera/extensions/context.kt

@@ -1,6 +1,8 @@
 package com.simplemobiletools.camera.extensions
 
 import android.content.Context
+import android.graphics.Point
+import android.view.WindowManager
 import com.simplemobiletools.camera.Config
 import java.io.File
 import java.text.SimpleDateFormat
@@ -8,6 +10,8 @@ import java.util.*
 
 val Context.config: Config get() = Config.newInstance(this)
 
+internal val Context.windowManager: WindowManager get() = getSystemService(Context.WINDOW_SERVICE) as WindowManager
+
 fun Context.getOutputMediaFile(isPhoto: Boolean): String {
     val mediaStorageDir = File(config.savePhotosFolder)
 
@@ -24,3 +28,17 @@ fun Context.getOutputMediaFile(isPhoto: Boolean): String {
         "${mediaStorageDir.path}${File.separator}VID_$timestamp.mp4"
     }
 }
+
+val Context.usableScreenSize: Point get() {
+    val size = Point()
+    windowManager.defaultDisplay.getSize(size)
+    return size
+}
+
+val Context.realScreenSize: Point get() {
+    val size = Point()
+    windowManager.defaultDisplay.getRealSize(size)
+    return size
+}
+
+val Context.navBarHeight: Int get() = realScreenSize.y - usableScreenSize.y