Android 圆形按钮实现

activity_main.xml

<RelativeLayout 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: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="com.example.circlebutton.MainActivity" >

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@drawable/button_corner"
        android:text="@string/circle_button"
        android:textColor="@android:color/white"
        android:textSize="18sp" />

</RelativeLayout>

button_corner.xml

<?xml version="1.0" encoding="UTF-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android" >

    <!-- 填充色 -->
    <solid android:color="#97C8E3" />

    <!-- 边距 -->
    <padding
        android:bottom="2dp"
        android:left="2dp"
        android:right="2dp"
        android:top="2dp" />

    <!-- 圆角 -->
    <corners android:radius="5dp" />

</shape>