android EditText实现圆弧背景

<EditText
android:id="@+id/o_item_num"
style="@style/ValueTextStyle"
android:hint="请输入服务次数"
android:layout_height="40.0dip"
android:inputType="number"
android:singleLine="true"
android:text="1" />

<style name="ValueTextStyle">
<item name="android:textSize">@dimen/txt_m</item>
<item name="android:background">@drawable/edit_bg_selector</item>
<item name="android:layout_width">fill_parent</item>
<item name="android:layout_height">wrap_content</item>
<item name="android:layout_marginLeft">15.0dip</item>
<item name="android:layout_marginTop">10.0dip</item>
<item name="android:layout_marginRight">15.0dip</item>
<item name="android:layout_marginBottom">10.0dip</item>
<item name="android:layout_centerVertical">true</item>
</style>

<?xml version="1.0" encoding="utf-8"?>
<selector
xmlns:android="http://schemas.android.com/apk/res/android">
<item android:state_enabled="false" android:drawable="@drawable/edit_text_disable" />
<item android:state_focused="true" android:drawable="@drawable/edit_text_focused" />
<item android:state_pressed="true" android:drawable="@drawable/edit_text_focused" />
<item android:drawable="@drawable/edit_text" />
</selector>