android:dataPath解析

位于res/drawable/face.xml

<vector
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:height="200dp"
    android:width="200dp"
    android:viewportHeight="100"
    android:viewportWidth="100" >
  <path
      android:strokeColor="@android:color/holo_red_dark"
      android:fillColor="@color/yellow"
      android:pathData="@string/path_circle"/>
  <path
      android:fillColor="@android:color/black"
      android:pathData="@string/path_face_left_eye"/>
  <path
      android:fillColor="@android:color/black"
      android:pathData="@string/path_face_right_eye"/>
  <path
      android:name="mouth"
      android:strokeColor="@android:color/black"
      android:strokeWidth="@integer/stroke_width"
      android:strokeLineCap="round"
      android:pathData="@string/path_face_mouth_sad"/>
</vector>

res/values/strings.xml

<string name="path_circle">
    M 50,50
    m -48,0
    a 48,48 0 1,0 96,0
    a 48,48 0 1,0 -96,0
  </string>
  <string name="path_face_left_eye">
    M 35,40
    m -7,0
    a 7,7 0 1,0 14,0
    a 7,7 0 1,0 -14,0
  </string>
  <string name="path_face_right_eye">
    M 65,40
    m -7,0
    a 7,7 0 1,0 14,0
    a 7,7 0 1,0 -14,0
  </string>
  <string name="path_face_mouth_sad">
    M 30,75
    Q 50,55 70,75
  </string>
  <string name="path_face_mouth_happy">
    M 30,65
    Q 50,85 70,65
  </string>

参考文章：
http://www.w3.org/TR/SVG/paths.html#PathData

M是移动的意思，大写代表绝对坐标，小写是相对坐标，注意相对的对象是其前一个对象。
a是画弧，48，48分别是所画弧的x,y轴的半径，0是x轴偏移量，1是取大弧，0是逆时针，（96，0）是终点坐标。 

下面的a同理。  <span style="font-family: Arial, Helvetica, sans-serif;">若将48全换成24，96全换成48，会看到圆的半径为原来的一半。 </span><span style="font-family: Arial, Helvetica, sans-serif;"> </span>