From ce4d1e43952cf1ba4980cce08213b2df6992f644 Mon Sep 17 00:00:00 2001
From: Pavel Shorokhov <p-ex@ya.ru>
Date: Mon, 9 Oct 2017 03:04:18 +0300
Subject: [PATCH] add recognition double-tap and single-finger-zoom

---
 .../photoview/PhotoViewAttacher.java          | 38 +++++++++++++------
 1 file changed, 27 insertions(+), 11 deletions(-)

diff --git a/photoview/src/main/java/com/github/chrisbanes/photoview/PhotoViewAttacher.java b/photoview/src/main/java/com/github/chrisbanes/photoview/PhotoViewAttacher.java
index 742b15d2..0e4038a9 100644
--- a/photoview/src/main/java/com/github/chrisbanes/photoview/PhotoViewAttacher.java
+++ b/photoview/src/main/java/com/github/chrisbanes/photoview/PhotoViewAttacher.java
@@ -20,6 +20,7 @@
 import android.graphics.Matrix.ScaleToFit;
 import android.graphics.RectF;
 import android.graphics.drawable.Drawable;
+import android.os.Handler;
 import android.support.v4.view.MotionEventCompat;
 import android.view.GestureDetector;
 import android.view.MotionEvent;
@@ -89,6 +90,7 @@ public class PhotoViewAttacher implements View.OnTouchListener,
     private float mBaseRotation;
 
     private boolean mZoomEnabled = true;
+    private boolean mTouchUpFired = false;
     private ScaleType mScaleType = ScaleType.FIT_CENTER;
 
     private OnGestureListener onGestureListener = new OnGestureListener() {
@@ -232,17 +234,30 @@ public boolean onSingleTapConfirmed(MotionEvent e) {
             @Override
             public boolean onDoubleTap(MotionEvent ev) {
                 try {
-                    float scale = getScale();
-                    float x = ev.getX();
-                    float y = ev.getY();
-
-                    if (scale < getMediumScale()) {
-                        setScale(getMediumScale(), x, y, true);
-                    } else if (scale >= getMediumScale() && scale < getMaximumScale()) {
-                        setScale(getMaximumScale(), x, y, true);
-                    } else {
-                        setScale(getMinimumScale(), x, y, true);
-                    }
+                    final float scale = getScale();
+                    final float x = ev.getX();
+                    final float y = ev.getY();
+
+                    // If after 50ms touchUp fires, gesture is completed double tap
+                    // Else gesture is single-finger-zoom, do nothing
+                    mTouchUpFired = false;
+                    new Handler().postDelayed(new Runnable() {
+                        @Override
+                        public void run() {
+                            if (mTouchUpFired) {
+                                // Double Tap Finished
+                                if (scale < getMediumScale()) {
+                                    setScale(getMediumScale(), x, y, true);
+                                } else if (scale >= getMediumScale() && scale < getMaximumScale()) {
+                                    setScale(getMaximumScale(), x, y, true);
+                                } else {
+                                    setScale(getMinimumScale(), x, y, true);
+                                }
+                            }
+                        }
+                    }, 50);
+
+
                 } catch (ArrayIndexOutOfBoundsException e) {
                     // Can sometimes happen when getX() and getY() is called
                 }
@@ -363,6 +378,7 @@ public boolean onTouch(View v, MotionEvent ev) {
                 case MotionEvent.ACTION_UP:
                     // If the user has zoomed less than min scale, zoom back
                     // to min scale
+                    mTouchUpFired = true;
                     if (getScale() < mMinScale) {
                         RectF rect = getDisplayRect();
                         if (rect != null) {