fix some glitches with swiping to sides with Instant media change enabled

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

@@ -61,6 +61,10 @@ class PhotoFragment : ViewPagerFragment() {
             gif_view.setOnClickListener { photoClicked() }
             instant_prev_item.setOnClickListener { listener?.goToPrevItem() }
             instant_next_item.setOnClickListener { listener?.goToNextItem() }
+
+            instant_prev_item.parentView = container
+            instant_next_item.parentView = container
+
             photo_brightness_controller.setOnTouchListener { v, event ->
                 mediaSideScroll.handleBrightnessTouched(event)
                 true

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

@@ -64,6 +64,8 @@ const val SLIDESHOW_SCROLL_DURATION = 500L
 const val NOMEDIA = ".nomedia"
 const val MAX_COLUMN_COUNT = 20
 const val SHOW_TEMP_HIDDEN_DURATION = 600000L
+const val CLICK_MAX_DURATION = 150
+const val DRAG_THRESHOLD = 10
 
 const val DIRECTORY = "directory"
 const val MEDIUM = "medium"

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

@@ -11,7 +11,6 @@ import com.simplemobiletools.gallery.activities.ViewPagerActivity
 import com.simplemobiletools.gallery.extensions.audioManager
 
 class MediaSideScroll(val activity: Activity, val slideInfoView: TextView, val callback: () -> Unit) {
-    private val CLICK_MAX_DURATION = 150
     private val SLIDE_INFO_FADE_DELAY = 1000L
     private var mTouchDownX = 0f
     private var mTouchDownY = 0f
@@ -38,7 +37,7 @@ class MediaSideScroll(val activity: Activity, val slideInfoView: TextView, val c
                 val diffX = mTouchDownX - event.x
                 val diffY = mTouchDownY - event.y
 
-                if (Math.abs(diffY) > 20 && Math.abs(diffY) > Math.abs(diffX)) {
+                if (Math.abs(diffY) > DRAG_THRESHOLD && Math.abs(diffY) > Math.abs(diffX)) {
                     var percent = ((diffY / ViewPagerActivity.screenHeight) * 100).toInt() * 3
                     percent = Math.min(100, Math.max(-100, percent))
 

app/src/main/kotlin/com/simplemobiletools/gallery/views/InstantItemSwitch.kt

@@ -0,0 +1,67 @@
+package com.simplemobiletools.gallery.views
+
+import android.content.Context
+import android.util.AttributeSet
+import android.view.MotionEvent
+import android.view.ViewGroup
+import android.widget.RelativeLayout
+import com.simplemobiletools.gallery.helpers.CLICK_MAX_DURATION
+import com.simplemobiletools.gallery.helpers.DRAG_THRESHOLD
+
+// handle only one finger clicks, pass other events to the parent view and ignore it when received again
+class InstantItemSwitch(context: Context, attrs: AttributeSet) : RelativeLayout(context, attrs) {
+    private var mTouchDownTime = 0L
+    private var mTouchDownX = 0f
+    private var mTouchDownY = 0f
+    private var passTouches = false
+
+    var parentView: ViewGroup? = null
+
+    override fun dispatchTouchEvent(ev: MotionEvent): Boolean {
+        if (passTouches) {
+            if (ev.actionMasked == MotionEvent.ACTION_DOWN) {
+                passTouches = false
+            }
+            return false
+        }
+        return super.dispatchTouchEvent(ev)
+    }
+
+    override fun onTouchEvent(event: MotionEvent): Boolean {
+        if (passTouches) {
+            return false
+        }
+
+        when (event.actionMasked) {
+            MotionEvent.ACTION_DOWN -> {
+                mTouchDownX = event.x
+                mTouchDownY = event.y
+                mTouchDownTime = System.currentTimeMillis()
+            }
+            MotionEvent.ACTION_UP -> {
+                if (System.currentTimeMillis() - mTouchDownTime < CLICK_MAX_DURATION) {
+                    performClick()
+                }
+            }
+            MotionEvent.ACTION_MOVE -> {
+                if (passTouches) {
+                    return false
+                }
+
+                val diffX = mTouchDownX - event.x
+                val diffY = mTouchDownY - event.y
+                if (Math.abs(diffX) > DRAG_THRESHOLD || Math.abs(diffY) > DRAG_THRESHOLD) {
+                    if (!passTouches) {
+                        event.action = MotionEvent.ACTION_DOWN
+                        event.setLocation(event.rawX, event.y)
+                        parentView?.dispatchTouchEvent(event)
+                    }
+                    passTouches = true
+                    parentView?.dispatchTouchEvent(event)
+                    return false
+                }
+            }
+        }
+        return true
+    }
+}

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

@@ -35,8 +35,8 @@
         android:id="@+id/photo_brightness_controller"
         android:layout_width="@dimen/media_side_slider_width"
         android:layout_height="match_parent"
-        android:layout_alignParentStart="true"
-        android:layout_alignParentLeft="true"/>
+        android:layout_alignParentLeft="true"
+        android:layout_alignParentStart="true"/>
 
     <TextView
         android:id="@+id/slide_info"
@@ -55,12 +55,12 @@
         android:textColor="@android:color/white"
         android:textSize="@dimen/extra_big_text_size"/>
 
-    <RelativeLayout
+    <com.simplemobiletools.gallery.views.InstantItemSwitch
         android:id="@+id/instant_prev_item"
         android:layout_width="@dimen/instant_change_bar_width"
         android:layout_height="match_parent"/>
 
-    <RelativeLayout
+    <com.simplemobiletools.gallery.views.InstantItemSwitch
         android:id="@+id/instant_next_item"
         android:layout_width="@dimen/instant_change_bar_width"
         android:layout_height="match_parent"