android 圆形按钮

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin" >

    <!-- 定义Button的控件-->
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@drawable/btn_bg"
        android:text="圆角按钮"
        />

</LinearLayout>

btn_bg.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle" >
    <!-- 定义按钮的背景的颜色 -->
    <solid android:color="#00CCFF" />
    <!-- 设置按钮的每个角的弧形角度 -->
    <corners android:radius="10dip" />
    <!-- 按钮文字与边界的距离 -->
    <padding
        android:bottom="5dp"
        android:left="5dp"
        android:right="5dp"
        android:top="5dp" />
</shape>