优化demo代码，demo添加代码使用示例

app/src/main/res/layout/item_choose_dir.xml

@@ -0,0 +1,31 @@
+<?xml version="1.0" encoding="utf-8"?>
+<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="@dimen/bar_height"
+    android:background="@drawable/item_bg"
+    android:orientation="vertical"
+    >
+
+  <android.support.v7.widget.AppCompatImageView
+      android:id="@+id/icon"
+      android:layout_width="@dimen/icon_size"
+      android:layout_height="@dimen/icon_size"
+      android:layout_centerVertical="true"
+      app:srcCompat="@drawable/ic_dir"
+      />
+
+  <TextView
+      android:id="@+id/text"
+      android:layout_width="wrap_content"
+      android:layout_height="wrap_content"
+      android:layout_centerVertical="true"
+      android:layout_marginLeft="8dp"
+      android:layout_toRightOf="@+id/icon"
+      android:ellipsize="marquee"
+      android:singleLine="true"
+      android:textColor="@color/text_black"
+      android:textSize="@dimen/text_size_normal"
+      />
+
+</RelativeLayout>