diff --git a/src/main/java/com/reandroid/arsc/chunk/TypeBlock.java b/src/main/java/com/reandroid/arsc/chunk/TypeBlock.java
index 5596046..cc04bdc 100755
--- a/src/main/java/com/reandroid/arsc/chunk/TypeBlock.java
+++ b/src/main/java/com/reandroid/arsc/chunk/TypeBlock.java
@@ -54,12 +54,9 @@ public class TypeBlock extends Chunk<TypeHeader>
         addChild(mEntryArray);
     }
     public PackageBlock getPackageBlock(){
-        Block parent=getParent();
-        while (parent!=null){
-            if(parent instanceof SpecTypePair){
-                return ((SpecTypePair)parent).getPackageBlock();
-            }
-            parent=parent.getParent();
+        SpecTypePair specTypePair = getParent(SpecTypePair.class);
+        if(specTypePair!=null){
+            return specTypePair.getPackageBlock();
         }
         return null;
     }
diff --git a/src/main/java/com/reandroid/arsc/chunk/xml/ResXmlElement.java b/src/main/java/com/reandroid/arsc/chunk/xml/ResXmlElement.java
index 3eb1adb..f4ce6ef 100755
--- a/src/main/java/com/reandroid/arsc/chunk/xml/ResXmlElement.java
+++ b/src/main/java/com/reandroid/arsc/chunk/xml/ResXmlElement.java
@@ -261,12 +261,9 @@
          return null;
      }
      public ResXmlIDMap getResXmlIDMap(){
-         Block parent=getParent();
-         while (parent!=null){
-             if(parent instanceof ResXmlDocument){
-                 return ((ResXmlDocument)parent).getResXmlIDMap();
-             }
-             parent=parent.getParent();
+         ResXmlDocument resXmlDocument = getParentInstance(ResXmlDocument.class);
+         if(resXmlDocument!=null){
+             return resXmlDocument.getResXmlIDMap();
          }
          return null;
      }
diff --git a/src/main/java/com/reandroid/arsc/chunk/xml/ResXmlIDMap.java b/src/main/java/com/reandroid/arsc/chunk/xml/ResXmlIDMap.java
index 21d8b49..a28670f 100755
--- a/src/main/java/com/reandroid/arsc/chunk/xml/ResXmlIDMap.java
+++ b/src/main/java/com/reandroid/arsc/chunk/xml/ResXmlIDMap.java
@@ -56,12 +56,9 @@
 
      }
      ResXmlStringPool getXmlStringPool(){
-         Block parent=this;
-         while (parent!=null){
-             if(parent instanceof ResXmlDocument){
-                 return ((ResXmlDocument)parent).getStringPool();
-             }
-             parent=parent.getParent();
+         ResXmlDocument resXmlDocument = getParentInstance(ResXmlDocument.class);
+         if(resXmlDocument!=null){
+             return resXmlDocument.getStringPool();
          }
          return null;
      }
diff --git a/src/main/java/com/reandroid/arsc/item/ResXmlID.java b/src/main/java/com/reandroid/arsc/item/ResXmlID.java
index 36e60a8..514c715 100755
--- a/src/main/java/com/reandroid/arsc/item/ResXmlID.java
+++ b/src/main/java/com/reandroid/arsc/item/ResXmlID.java
@@ -72,12 +72,9 @@ public class ResXmlID extends IntegerItem {
         return stringPool.get(getIndex());
     }
     private ResXmlStringPool getXmlStringPool(){
-        Block parent=this;
-        while (parent!=null){
-            if(parent instanceof ResXmlDocument){
-                return ((ResXmlDocument)parent).getStringPool();
-            }
-            parent=parent.getParent();
+        ResXmlDocument resXmlDocument = getParentInstance(ResXmlDocument.class);
+        if(resXmlDocument!=null){
+            return resXmlDocument.getStringPool();
         }
         return null;
     }
diff --git a/src/main/java/com/reandroid/arsc/item/StringItem.java b/src/main/java/com/reandroid/arsc/item/StringItem.java
index b349f05..4231e91 100755
--- a/src/main/java/com/reandroid/arsc/item/StringItem.java
+++ b/src/main/java/com/reandroid/arsc/item/StringItem.java
@@ -218,23 +218,13 @@ public class StringItem extends BlockItem implements JSONConvert<JSONObject> {
         return styleItem.getSpanInfoList().size()>0;
     }
     public StyleItem getStyle(){
-        StringPool<?> stringPool=getStringPool();
+        StringPool<?> stringPool = getParentInstance(StringPool.class);
         if(stringPool==null){
             return null;
         }
         int index=getIndex();
         return stringPool.getStyle(index);
     }
-    private StringPool<?> getStringPool(){
-        Block parent=getParent();
-        while (parent!=null){
-            if(parent instanceof StringPool){
-                return (StringPool<?>)parent;
-            }
-            parent=parent.getParent();
-        }
-        return null;
-    }
     @Override
     public JSONObject toJson() {
         if(isNull()){
diff --git a/src/main/java/com/reandroid/arsc/item/StyleItem.java b/src/main/java/com/reandroid/arsc/item/StyleItem.java
index 24b045f..4e6ce91 100755
--- a/src/main/java/com/reandroid/arsc/item/StyleItem.java
+++ b/src/main/java/com/reandroid/arsc/item/StyleItem.java
@@ -263,14 +263,7 @@ public class StyleItem extends IntegerArray implements JSONConvert<JSONObject> {
         return null;
     }
     private StringPool<?> getStringPool(){
-        Block parent=getParent();
-        while (parent!=null){
-            if(parent instanceof StringPool){
-                return (StringPool<?>)parent;
-            }
-            parent=parent.getParent();
-        }
-        return null;
+        return getParentInstance(StringPool.class);
     }
 
     public String applyHtml(String str, boolean xml){
diff --git a/src/main/java/com/reandroid/arsc/pool/SpecStringPool.java b/src/main/java/com/reandroid/arsc/pool/SpecStringPool.java
index 3d5e0c7..157278d 100755
--- a/src/main/java/com/reandroid/arsc/pool/SpecStringPool.java
+++ b/src/main/java/com/reandroid/arsc/pool/SpecStringPool.java
@@ -33,13 +33,6 @@ public class SpecStringPool extends StringPool<SpecString> {
         return new SpecStringArray(offsets, itemCount, itemStart, is_utf8);
     }
     public PackageBlock getPackageBlock(){
-        Block parent=getParent();
-        while (parent!=null){
-            if(parent instanceof PackageBlock){
-                return (PackageBlock) parent;
-            }
-            parent=parent.getParent();
-        }
-        return null;
+        return getParent(PackageBlock.class);
     }
 }
diff --git a/src/main/java/com/reandroid/arsc/pool/StringPool.java b/src/main/java/com/reandroid/arsc/pool/StringPool.java
index 61dd028..f8436a3 100755
--- a/src/main/java/com/reandroid/arsc/pool/StringPool.java
+++ b/src/main/java/com/reandroid/arsc/pool/StringPool.java
@@ -140,6 +140,13 @@ package com.reandroid.arsc.pool;
             group.add(item);
         }
     }
+    void updateUniqueIdMap(T item){
+        if(item==null){
+            return;
+        }
+        StringGroup<T> group = getOrCreateGroup(item.getHtml());
+        group.add(item);
+    }
     public List<T> removeUnusedStrings(){
         return getStringsArray().removeUnusedStrings();
     }