diff --git a/app/src/main/java/com/hippo/ehviewer/ehclient/ExDownloader.java b/app/src/main/java/com/hippo/ehviewer/ehclient/ExDownloader.java
index a74e5aaba..02cce170b 100644
--- a/app/src/main/java/com/hippo/ehviewer/ehclient/ExDownloader.java
+++ b/app/src/main/java/com/hippo/ehviewer/ehclient/ExDownloader.java
@@ -51,11 +51,9 @@ public final class ExDownloader implements Runnable {
 
     private static final int IO_BUFFER_SIZE = 8 * 1024;
 
-    private static final String[] URL_ARRAY_509 = new String[] {
-        "http://ehgt.org/g/509.gif",
-        "http://ehgt.org/g/509s.gif",
-        "http://st.exhentai.net/img/509.gif",
-        "http://st.exhentai.net/img/509s.gif"
+    private static final String[] URL_509_SUFFIX_ARRAY = {
+            "/509.gif",
+            "/509s.gif"
     };
 
     private final Context mContext;
@@ -786,9 +784,8 @@ public final class ExDownloader implements Runnable {
 
                             //Check 509 gif
                             boolean get509 = false;
-                            int length = URL_ARRAY_509.length;
-                            for (int j = 0; j < length; j++) {
-                                if (URL_ARRAY_509[j].equals(imageUrl)) {
+                            for (String suffix : URL_509_SUFFIX_ARRAY) {
+                                if (imageUrl.endsWith(suffix)) {
                                     // Get 509 gif here
                                     get509 = true;
                                     break;
diff --git a/app/src/main/java/com/hippo/ehviewer/gallery/data/ImageSet.java b/app/src/main/java/com/hippo/ehviewer/gallery/data/ImageSet.java
index 75307d24c..c22287c5a 100644
--- a/app/src/main/java/com/hippo/ehviewer/gallery/data/ImageSet.java
+++ b/app/src/main/java/com/hippo/ehviewer/gallery/data/ImageSet.java
@@ -16,13 +16,8 @@
 
 package com.hippo.ehviewer.gallery.data;
 
-import java.io.File;
-import java.util.Queue;
-import java.util.concurrent.ConcurrentLinkedQueue;
-
 import android.graphics.BitmapFactory;
 import android.graphics.Movie;
-import android.util.SparseArray;
 
 import com.hippo.ehviewer.AppHandler;
 import com.hippo.ehviewer.ehclient.ExDownloader;
@@ -35,6 +30,12 @@ import com.hippo.ehviewer.util.EhUtils;
 import com.hippo.ehviewer.util.Log;
 import com.hippo.ehviewer.util.Utils;
 
+import java.io.File;
+import java.util.Map;
+import java.util.Queue;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentLinkedQueue;
+
 public class ImageSet implements ExDownloader.ListenerForImageSet {
 
     private static final String TAG = ImageSet.class.getSimpleName();
@@ -52,8 +53,8 @@ public class ImageSet implements ExDownloader.ListenerForImageSet {
     private final File mDir;
     private final AutoExpandArray<String> mImageFilenameArray;
     private ImageListener mListener;
-    private final Queue<DecodeInfo> mDecodeQueue = new ConcurrentLinkedQueue<DecodeInfo>();
-    private final SparseArray<Float> mPercentMap = new SparseArray<Float>(5);
+    private final Queue<DecodeInfo> mDecodeQueue = new ConcurrentLinkedQueue<>();
+    private final Map<Integer, Float> mPercentMap = new ConcurrentHashMap<>(5);
     private final DecodeWorker mDecodeWorker;
     /** If true, then wake Worker, worker will stop **/
     private volatile boolean mStopWork = false;
@@ -266,8 +267,7 @@ public class ImageSet implements ExDownloader.ListenerForImageSet {
 
     @Override
     public void onDownloading(final int index, final float percent) {
-        mPercentMap.append(index, percent);
-
+        mPercentMap.put(index, percent);
         AppHandler.getInstance().post(new Runnable() {
             @Override
             public void run() {