R文件丢失问题，不能生成R文件

Question

[2017-03-19 20:01:24 - UploadActivity] W/ResourceType( 4940): ResXMLTree_node header size 0 is too small.
[2017-03-19 20:01:24 - UploadActivity] E:\workspaceHeiMa\term38\day5\UploadActivity\res\menu\main.xml:3: error: Error: No resource found that matches the given name (at 'title' with value '@string/action_settings').

xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".UploadActivity" >

android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/filename"
/>

<EditText
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="WinRAR_3.90_SC.exe"
    android:id="@+id/filename"
    />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/button"
    android:id="@+id/button"
    />
<ProgressBar
    android:layout_width="fill_parent"
    android:layout_height="20px"
    style="?android:attr/progressBarStyleHorizontal"
    android:id="@+id/uploadbar"
    />
<TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:gravity="center"
    android:id="@+id/result"
    />

<?xml version="1.0" encoding="utf-8"?>

 <string  name="hello">Hello  World,  UploadActivity!</string>
<string  name="app_name">大视频文件断点上传</string>
<string  name="filename">文件名称</string>
<string  name="button">上传</string>
<string  name="sdcarderror">SDCard不存在或者写保护</string>
<string  name="success">上传完成</string>
<string  name="error">上传失败</string>
<string  name="filenotexsit">文件不存在</string>

Answer 1

<item
    android:id="@+id/action_settings"
    android:orderInCategory="100"
    android:showAsAction="never"
    android:title="@string/action_settings"/>