ndroid:screenOrientation="landscape"是限制此页面横屏显示， 
ndroid:screenOrientation="portrait"是限制此页面数竖屏显示。 
例如：我现在想让所有的页面不管怎么样都竖屏显示，则我的AndroidManifest.xml应该这样写： 
<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
      package="com.oa" 
      android:versionCode="1" 
      android:versionName="1.0"> 
    <application android:icon="@drawable/icon" android:label="@string/app_name"> 
        <activity android:name=".OaDemo" 
                  android:label="@string/app_name" 
                  android:screenOrientation="portrait"> 
            <intent-filter> 
                <action android:name="android.intent.action.MAIN" /> 
                <category android:name="android.intent.category.LAUNCHER" /> 
            </intent-filter> 
        </activity> 
    <activity android:name="MyDocuments" android:screenOrientation="portrait"></activity> 
    <activity android:name="ReimbursementRecords" android:screenOrientation="portrait"></activity> 
    <activity android:name="SecondActivty" android:screenOrientation="portrait"></activity> 
    <activity android:name="ChildReimbursementRecords" android:screenOrientation="portrait"></activity> 
    </application> 
</manifest>