Apply thumb size settings to preview size

app/src/main/java/com/hippo/ehviewer/Settings.java

@@ -21,6 +21,7 @@ import android.content.Context;
 import android.content.SharedPreferences;
 import android.net.Uri;
 import android.preference.PreferenceManager;
+import android.support.annotation.DimenRes;
 import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
 import android.util.Log;
@@ -261,6 +262,19 @@ public class Settings {
         return getIntFromStr(KEY_THUMB_SIZE, DEFAULT_THUMB_SIZE);
     }
 
+    @DimenRes
+    public static int getThumbSizeResId() {
+        switch (getThumbSize()) {
+            case 0:
+                return R.dimen.gallery_grid_column_width_large;
+            default:
+            case 1:
+                return R.dimen.gallery_grid_column_width_middle;
+            case 2:
+                return R.dimen.gallery_grid_column_width_small;
+        }
+    }
+
     private static final String KEY_SHOW_JPN_TITLE = "show_jpn_title";
     private static final boolean DEFAULT_SHOW_JPN_TITLE = false;