implement the "Focus before capture" functionality

app/src/main/kotlin/com/simplemobiletools/camera/Preview.kt

@@ -256,7 +256,15 @@ class Preview : ViewGroup, SurfaceHolder.Callback, MediaScannerConnection.OnScan
         })
     }
 
-    fun takePicture() {
+    fun tryTakePicture() {
+        if (config.focusBeforeCapture) {
+            focusArea(true)
+        } else {
+            takePicture()
+        }
+    }
+
+    private fun takePicture() {
         if (mCanTakePicture) {
             val selectedResolution = getSelectedResolution()
             mParameters!!.setPictureSize(selectedResolution.width, selectedResolution.height);

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

@@ -269,7 +269,7 @@ class MainActivity : SimpleActivity(), PreviewListener, PhotoProcessor.MediaSave
     private fun handleShutter() {
         if (mIsInPhotoMode) {
             toggleBottomButtons(true)
-            mPreview?.takePicture()
+            mPreview?.tryTakePicture()
             Handler().postDelayed({
                 toggleBottomButtons(false)
             }, Preview.PHOTO_PREVIEW_LENGTH)