added one finger zooming

app/src/main/kotlin/com/simplemobiletools/gallery/activities/SettingsActivity.kt

@@ -59,6 +59,7 @@ class SettingsActivity : SimpleActivity() {
         setupShowInfoBubble()
         setupShowExtendedDetails()
         setupManageExtendedDetails()
+        setupOneFingerZoom()
         updateTextColors(settings_holder)
     }
 
@@ -312,4 +313,12 @@ class SettingsActivity : SimpleActivity() {
             }
         }
     }
+
+    private fun setupOneFingerZoom() {
+        settings_one_finger_zoom.isChecked = config.oneFingerZoom
+        settings_one_finger_zoom_holder.setOnClickListener {
+            settings_one_finger_zoom.toggle()
+            config.oneFingerZoom = settings_one_finger_zoom.isChecked
+        }
+    }
 }

app/src/main/kotlin/com/simplemobiletools/gallery/fragments/PhotoFragment.kt

@@ -246,7 +246,7 @@ class PhotoFragment : ViewPagerFragment() {
             view.subsampling_view.apply {
                 maxScale = 10f
                 beVisible()
-                isQuickScaleEnabled = false
+                isQuickScaleEnabled = context.config.oneFingerZoom
                 setImage(ImageSource.uri(medium.path))
                 orientation = if (orient == -1) SubsamplingScaleImageView.ORIENTATION_USE_EXIF else degreesForRotation(orient)
                 setOnImageEventListener(object : SubsamplingScaleImageView.OnImageEventListener {

app/src/main/kotlin/com/simplemobiletools/gallery/helpers/Config.kt

@@ -168,6 +168,10 @@ class Config(context: Context) : BaseConfig(context) {
         get() = prefs.getInt(getDirectoryColumnsField(), getDefaultDirectoryColumnCount())
         set(dirColumnCnt) = prefs.edit().putInt(getDirectoryColumnsField(), dirColumnCnt).apply()
 
+    var oneFingerZoom: Boolean
+        get() = prefs.getBoolean(ONE_FINGER_ZOOM, false)
+        set(loop) = prefs.edit().putBoolean(ONE_FINGER_ZOOM, loop).apply()
+
     private fun getDirectoryColumnsField(): String {
         val isPortrait = context.resources.configuration.orientation == Configuration.ORIENTATION_PORTRAIT
         return if (isPortrait) {

app/src/main/kotlin/com/simplemobiletools/gallery/helpers/Constants.kt

@@ -43,6 +43,7 @@ val VIEW_TYPE_FILES = "view_type_files"
 val SHOW_EXTENDED_DETAILS = "show_extended_details"
 val EXTENDED_DETAILS = "extended_details"
 val LAST_FILE_CLEANUP = "last_file_cleanup"
+val ONE_FINGER_ZOOM = "one_finger_zoom"
 
 // slideshow
 val SLIDESHOW_INTERVAL = "slideshow_interval"

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

@@ -464,6 +464,25 @@
                 android:paddingLeft="@dimen/medium_margin"
                 android:paddingStart="@dimen/medium_margin"
                 android:text="@string/show_extended_details"/>
+        </RelativeLayout>
+
+        <RelativeLayout
+            android:id="@+id/settings_one_finger_zoom_holder"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="@dimen/medium_margin"
+            android:background="?attr/selectableItemBackground"
+            android:padding="@dimen/activity_margin">
+
+            <com.simplemobiletools.commons.views.MySwitchCompat
+                android:id="@+id/settings_one_finger_zoom"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:background="@null"
+                android:clickable="false"
+                android:paddingLeft="@dimen/medium_margin"
+                android:paddingStart="@dimen/medium_margin"
+                android:text="@string/one_finger_zoom"/>
 
         </RelativeLayout>
 

app/src/main/res/values/strings.xml

@@ -146,6 +146,7 @@
 
         This app is just one piece of a bigger series of apps. You can find the rest of them at http://www.simplemobiletools.com
     </string>
+    <string name="one_finger_zoom">Toggle one finger zoom</string>
 
     <!--
         Haven't found some strings? There's more at