diff --git a/gradlew b/gradlew
old mode 100644
new mode 100755
diff --git a/library/src/main/java/com/hippo/unifile/AssetFile.java b/library/src/main/java/com/hippo/unifile/AssetFile.java
index c22ecd9..115485a 100644
--- a/library/src/main/java/com/hippo/unifile/AssetFile.java
+++ b/library/src/main/java/com/hippo/unifile/AssetFile.java
@@ -57,7 +57,7 @@ public UniFile createFile(String displayName) {
 
     @Override
     public UniFile createDirectory(String displayName) {
-        UniFile file = findFile(displayName, true);
+        UniFile file = findFile(displayName);
         if (file != null && file.isDirectory()) {
             return file;
         } else {
@@ -208,12 +208,6 @@ public UniFile[] listFiles(FilenameFilter filter) {
     @Nullable
     @Override
     public UniFile findFile(String displayName) {
-        return findFile(displayName, false);
-    }
-
-    @Nullable
-    @Override
-    public UniFile findFile(String displayName, boolean ignoreCase) {
         if (TextUtils.isEmpty(displayName)) {
             return null;
         }
@@ -225,7 +219,7 @@ public UniFile findFile(String displayName, boolean ignoreCase) {
             }
 
             for (String f : files) {
-                if (Utils.equals(displayName, f, ignoreCase)) {
+                if (displayName.equals(f)) {
                     return new AssetFile(this, mAssetManager, Utils.resolve(mPath, displayName));
                 }
             }
diff --git a/library/src/main/java/com/hippo/unifile/MediaFile.java b/library/src/main/java/com/hippo/unifile/MediaFile.java
index b6894cd..1ef832f 100644
--- a/library/src/main/java/com/hippo/unifile/MediaFile.java
+++ b/library/src/main/java/com/hippo/unifile/MediaFile.java
@@ -146,11 +146,6 @@ public UniFile findFile(String displayName) {
         return null;
     }
 
-    @Override
-    public UniFile findFile(String displayName, boolean ignoreCase) {
-        return null;
-    }
-
     @Override
     public boolean renameTo(String displayName) {
         return false;
diff --git a/library/src/main/java/com/hippo/unifile/RawFile.java b/library/src/main/java/com/hippo/unifile/RawFile.java
index 79504c4..940fb63 100644
--- a/library/src/main/java/com/hippo/unifile/RawFile.java
+++ b/library/src/main/java/com/hippo/unifile/RawFile.java
@@ -189,11 +189,6 @@ public UniFile[] listFiles(FilenameFilter filter) {
 
     @Override
     public UniFile findFile(String displayName) {
-        return findFile(displayName, false);
-    }
-
-    @Override
-    public UniFile findFile(String displayName, boolean ignoreCase) {
         if (TextUtils.isEmpty(displayName)) {
             return null;
         }
diff --git a/library/src/main/java/com/hippo/unifile/ResourceFile.java b/library/src/main/java/com/hippo/unifile/ResourceFile.java
index a23b535..b905b69 100644
--- a/library/src/main/java/com/hippo/unifile/ResourceFile.java
+++ b/library/src/main/java/com/hippo/unifile/ResourceFile.java
@@ -144,12 +144,6 @@ public UniFile findFile(String displayName) {
         return null;
     }
 
-    @Nullable
-    @Override
-    public UniFile findFile(String displayName, boolean ignoreCase) {
-        return null;
-    }
-
     @Override
     public boolean renameTo(String displayName) {
         return false;
diff --git a/library/src/main/java/com/hippo/unifile/SingleDocumentFile.java b/library/src/main/java/com/hippo/unifile/SingleDocumentFile.java
index 06bd93e..956d60f 100644
--- a/library/src/main/java/com/hippo/unifile/SingleDocumentFile.java
+++ b/library/src/main/java/com/hippo/unifile/SingleDocumentFile.java
@@ -131,11 +131,6 @@ public UniFile findFile(String displayName) {
         return null;
     }
 
-    @Override
-    public UniFile findFile(String displayName, boolean ignoreCase) {
-        return null;
-    }
-
     @Override
     public boolean renameTo(String displayName) {
         return false;
diff --git a/library/src/main/java/com/hippo/unifile/TreeDocumentFile.java b/library/src/main/java/com/hippo/unifile/TreeDocumentFile.java
index 2c54af7..bbcdc60 100644
--- a/library/src/main/java/com/hippo/unifile/TreeDocumentFile.java
+++ b/library/src/main/java/com/hippo/unifile/TreeDocumentFile.java
@@ -19,6 +19,7 @@
 import android.content.Context;
 import android.net.Uri;
 import android.os.ParcelFileDescriptor;
+import android.provider.DocumentsContract;
 import android.text.TextUtils;
 import android.util.Log;
 import android.webkit.MimeTypeMap;
@@ -93,7 +94,7 @@ public UniFile createDirectory(String displayName) {
             return null;
         }
 
-        UniFile child = findFile(displayName, true);
+        UniFile child = findFile(displayName);
 
         if (child != null) {
             if (child.isDirectory()) {
@@ -220,11 +221,6 @@ public UniFile[] listFiles(FilenameFilter filter) {
 
     @Override
     public UniFile findFile(String displayName) {
-        return findFile(displayName, false);
-    }
-
-    @Override
-    public UniFile findFile(String displayName, boolean ignoreCase) {
         if (TextUtils.isEmpty(displayName)) {
             return null;
         }
@@ -233,13 +229,17 @@ public UniFile findFile(String displayName, boolean ignoreCase) {
             return null;
         }
 
-        final NamedUri[] result = DocumentsContractApi21.listFilesNamed(mContext, mUri);
-        for (NamedUri uri : result) {
-            if (Utils.equals(displayName, uri.name, ignoreCase)) {
-                return new TreeDocumentFile(this, mContext, uri.uri, displayName);
-            }
+        String documentId = DocumentsContract.getDocumentId(mUri);
+        documentId += "/" + displayName;
+
+        Uri documentUri = DocumentsContract.buildDocumentUriUsingTree(mUri, documentId);
+        UniFile child = new TreeDocumentFile(this, mContext, documentUri, displayName);
+
+        if (child.exists()) {
+            return child;
+        } else {
+            return null;
         }
-        return null;
     }
 
     @Override
diff --git a/library/src/main/java/com/hippo/unifile/UniFile.java b/library/src/main/java/com/hippo/unifile/UniFile.java
index e709edf..8af1d9e 100644
--- a/library/src/main/java/com/hippo/unifile/UniFile.java
+++ b/library/src/main/java/com/hippo/unifile/UniFile.java
@@ -402,15 +402,6 @@ public UniFile getParentFile() {
     @Nullable
     public abstract UniFile findFile(String displayName);
 
-    /**
-     * Test there is a file with the display name in the directory.
-     *
-     * @param ignoreCase Whether to do a case insensitive check.
-     * @return the file if found it, or {@code null}.
-     */
-    @Nullable
-    public abstract UniFile findFile(String displayName, boolean ignoreCase);
-
     /**
      * Renames this file to {@code displayName}.
      * <p>