diff --git a/.idea/misc.xml b/.idea/misc.xml
index 2f486ebd0..e1d91222a 100644
--- a/.idea/misc.xml
+++ b/.idea/misc.xml
@@ -3,8 +3,31 @@
   <component name="EntryPointsManager">
     <entry_points version="2.0" />
   </component>
+  <component name="NullableNotNullManager">
+    <option name="myDefaultNullable" value="org.jetbrains.annotations.Nullable" />
+    <option name="myDefaultNotNull" value="android.support.annotation.NonNull" />
+    <option name="myNullables">
+      <value>
+        <list size="4">
+          <item index="0" class="java.lang.String" itemvalue="org.jetbrains.annotations.Nullable" />
+          <item index="1" class="java.lang.String" itemvalue="javax.annotation.Nullable" />
+          <item index="2" class="java.lang.String" itemvalue="edu.umd.cs.findbugs.annotations.Nullable" />
+          <item index="3" class="java.lang.String" itemvalue="android.support.annotation.Nullable" />
+        </list>
+      </value>
+    </option>
+    <option name="myNotNulls">
+      <value>
+        <list size="4">
+          <item index="0" class="java.lang.String" itemvalue="org.jetbrains.annotations.NotNull" />
+          <item index="1" class="java.lang.String" itemvalue="javax.annotation.Nonnull" />
+          <item index="2" class="java.lang.String" itemvalue="edu.umd.cs.findbugs.annotations.NonNull" />
+          <item index="3" class="java.lang.String" itemvalue="android.support.annotation.NonNull" />
+        </list>
+      </value>
+    </option>
+  </component>
   <component name="ProjectRootManager" version="2" languageLevel="JDK_1_7" assert-keyword="true" jdk-15="true" project-jdk-name="1.7" project-jdk-type="JavaSDK">
     <output url="file://$PROJECT_DIR$/build/classes" />
   </component>
-</project>
-
+</project>
\ No newline at end of file
diff --git a/app/src/main/java/com/hippo/util/AppConfig.java b/app/src/main/java/com/hippo/ehviewer/AppConfig.java
similarity index 55%
rename from app/src/main/java/com/hippo/util/AppConfig.java
rename to app/src/main/java/com/hippo/ehviewer/AppConfig.java
index ff1777c6e..710dd6a42 100644
--- a/app/src/main/java/com/hippo/util/AppConfig.java
+++ b/app/src/main/java/com/hippo/ehviewer/AppConfig.java
@@ -13,7 +13,7 @@
  * limitations under the License.
  */
 
-package com.hippo.util;
+package com.hippo.ehviewer;
 
 import android.os.Environment;
 import android.support.annotation.Nullable;
@@ -25,23 +25,40 @@ import java.io.File;
  */
 public final class AppConfig {
 
-    private static final String APP_FOLDER_NAME = "EhViewer";
+    private static final String APP_DIRNAME = "EhViewer";
+    private static final String CRASH_DIRNAME = "crash";
+    private static final String DOWNLOAD_DIRNAME = "download";
+    private static final String TORRENT_DIRNAME = "torrent";
 
-    public static @Nullable File getAppFolder() {
+    public static @Nullable
+    File getAppDir() {
         if (Environment.getExternalStorageState()
-                .equals(android.os.Environment.MEDIA_MOUNTED)) {
-            return new File(Environment.getExternalStorageDirectory(), APP_FOLDER_NAME);
+                .equals(Environment.MEDIA_MOUNTED)) {
+            return new File(Environment.getExternalStorageDirectory(), APP_DIRNAME);
         } else {
             return null;
         }
     }
 
-    public static @Nullable File getFileInAppFolder(String filename) {
-        File appFolder = getAppFolder();
+    public static @Nullable File getFileInAppDir(String filename) {
+        File appFolder = getAppDir();
         if (appFolder != null) {
             return new File(appFolder, filename);
         } else {
             return null;
         }
     }
+
+    public static @Nullable File getCrashDir() {
+        return getFileInAppDir(CRASH_DIRNAME);
+    }
+
+    public static @Nullable File getDownloadDir() {
+        return getFileInAppDir(DOWNLOAD_DIRNAME);
+    }
+
+    public static @Nullable File getTorrentDir() {
+        return getFileInAppDir(TORRENT_DIRNAME);
+    }
 }
+
diff --git a/app/src/main/java/com/hippo/util/Log.java b/app/src/main/java/com/hippo/util/Log.java
index 4c0d9c027..34284edce 100644
--- a/app/src/main/java/com/hippo/util/Log.java
+++ b/app/src/main/java/com/hippo/util/Log.java
@@ -17,6 +17,7 @@ package com.hippo.util;
 
 import android.os.Process;
 
+import com.hippo.ehviewer.AppConfig;
 import com.hippo.ehviewer.BuildConfig;
 
 import java.io.File;
@@ -34,6 +35,7 @@ public class Log {
     private static final String TAG = Log.class.getSimpleName();
 
     private static final String NO_MESSAGE = "No Message";
+    private static final String LOG_FILENAME = "ehviewer.log";
 
     private static final SaveLogThreadExecutor sSaveLogThreadPool;
     private static final Pool<SaveMsgTask> sSaveLogTaskPool;
@@ -47,7 +49,7 @@ public class Log {
         sSaveLogThreadPool = new SaveLogThreadExecutor();
         sSaveLogTaskPool = new Pool<>(10);
         sDataFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS", Locale.ENGLISH);
-        sLogFile = AppConfig.getFileInAppFolder("ehviewer.log");
+        sLogFile = AppConfig.getFileInAppDir(LOG_FILENAME);
         sSupportSaveLog = FileUtils.ensureFile(sLogFile);
     }