更改app的主题

<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.example.lifetimeactivity.MainActivity"
android:label="@string/app_name"
android:theme="@android:style/Theme.Wallpaper" >  <!-- 这里更改 -->
<intent-filter>
<action android:name="android.intent.action.MAIN" />

<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>