Add gallery image cache

app/src/main/java/com/hippo/ehviewer/gallery/ZipGalleryProvider.java

@@ -85,7 +85,7 @@ public class ZipGalleryProvider extends GalleryProvider implements Runnable {
     }
 
     @Override
-    public void request(int index) {
+    protected void onRequest(int index) {
         synchronized (mRequests) {
             if (!mRequests.contains(index) && index != mDecodingIndex.get()) {
                 mRequests.add(index);
@@ -96,7 +96,12 @@ public class ZipGalleryProvider extends GalleryProvider implements Runnable {
     }
 
     @Override
-    public void cancelRequest(int index) {
+    protected void onForceRequest(int index) {
+        onRequest(index);
+    }
+
+    @Override
+    protected void onCancelRequest(int index) {
         synchronized (mRequests) {
             mRequests.remove(Integer.valueOf(index));
         }