Fix updating of all slides even it is not necessary.

Change-Id: I6f7937296915a7cff71d9d9ee491736a0c2c31be

2 files changed, 28 insertions, 2 deletions

diff --git a/android/sdremote/src/org/libreoffice/impressremote/adapter/SlidesPagerAdapter.java b/android/sdremote/src/org/libreoffice/impressremote/adapter/SlidesPagerAdapter.java
index 02097d27a743..be6f84fcc974 100644
--- a/android/sdremote/src/org/libreoffice/impressremote/adapter/SlidesPagerAdapter.java
+++ b/android/sdremote/src/org/libreoffice/impressremote/adapter/SlidesPagerAdapter.java
@@ -85,7 +85,7 @@ public class SlidesPagerAdapter extends PagerAdapter {
 
     @Override
     public int getItemPosition(Object aObject) {
-        // TODO: think about it, seems like a hack
+        // There seems no other way to update slides with notifyDataSetChanged.
 
         return POSITION_NONE;
     }
diff --git a/android/sdremote/src/org/libreoffice/impressremote/fragment/SlidesPagerFragment.java b/android/sdremote/src/org/libreoffice/impressremote/fragment/SlidesPagerFragment.java
index 838245a0d35b..0c2280102afc 100644
--- a/android/sdremote/src/org/libreoffice/impressremote/fragment/SlidesPagerFragment.java
+++ b/android/sdremote/src/org/libreoffice/impressremote/fragment/SlidesPagerFragment.java
@@ -200,7 +200,9 @@ public class SlidesPagerFragment extends SherlockFragment implements ServiceConn
             }
 
             if (Intents.Actions.SLIDE_PREVIEW.equals(aIntent.getAction())) {
-                mSlidesPagerFragment.refreshSlidesPager();
+                int aSlideIndex = aIntent.getIntExtra(Intents.Extras.SLIDE_INDEX, 0);
+
+                mSlidesPagerFragment.refreshSlide(aSlideIndex);
             }
         }
     }
@@ -221,6 +223,30 @@ public class SlidesPagerFragment extends SherlockFragment implements ServiceConn
         return LocalBroadcastManager.getInstance(aContext);
     }
 
+    private void refreshSlide(int aSlideIndex) {
+        // Refresh only loaded slides to avoid images blinking on large slides count.
+        // There is no way to invalidate only a certain slide.
+
+        int aCurrentSlideIndex = mCommunicationService.getSlideShow().getCurrentSlideIndex();
+
+        if (aSlideIndex == aCurrentSlideIndex) {
+            refreshSlidesPager();
+            return;
+        }
+
+        int aSlidesOffscreenCount = getSlidesPager().getOffscreenPageLimit();
+
+        if (aSlideIndex < aCurrentSlideIndex - aSlidesOffscreenCount) {
+            return;
+        }
+
+        if (aSlideIndex > aCurrentSlideIndex + aSlidesOffscreenCount) {
+            return;
+        }
+
+        refreshSlidesPager();
+    }
+
     private void refreshSlidesPager() {
         getSlidesPager().getAdapter().notifyDataSetChanged();
     }