参考：http://stackoverflow.com/questions/19691530/valid-values-for-androidfontfamily-and-what-they-map-to?answertab=votes#tab-top

一共有12种组合

Added in Android Jelly Bean (4.1) - API 16 :

Regular (default):

<item name="android:fontFamily">sans-serif</item>
<item name="android:textStyle">normal</item> 

Italic:

<item name="android:fontFamily">sans-serif</item>
<item name="android:textStyle">italic</item>

Bold:

<item name="android:fontFamily">sans-serif</item>
<item name="android:textStyle">bold</item>

Bold-italic:

<item name="android:fontFamily">sans-serif</item>
<item name="android:textStyle">bold|italic</item>

Light:

<item name="android:fontFamily">sans-serif-light</item>
<item name="android:textStyle">normal</item>

Light-italic:

<item name="android:fontFamily">sans-serif-light</item>
<item name="android:textStyle">italic</item>

Thin :

<item name="android:fontFamily">sans-serif-thin</item>
<item name="android:textStyle">normal</item>

Thin-italic :

<item name="android:fontFamily">sans-serif-thin</item>
<item name="android:textStyle">italic</item>

Condensed regular:

<item name="android:fontFamily">sans-serif-condensed</item>
<item name="android:textStyle">normal</item>

Condensed italic:

<item name="android:fontFamily">sans-serif-condensed</item>
<item name="android:textStyle">italic</item>

Condensed bold:

<item name="android:fontFamily">sans-serif-condensed</item>
<item name="android:textStyle">bold</item>

Condensed bold-italic:

<item name="android:fontFamily">sans-serif-condensed</item>
<item name="android:textStyle">bold|italic</item>

Added in Android Lollipop (v5.0) - API 21 :

Medium:

<item name="android:fontFamily">sans-serif-medium</item>
<item name="android:textStyle">normal</item>

Medium-italic:

<item name="android:fontFamily">sans-serif-medium</item>
<item name="android:textStyle">italic</item>

Black:

<item name="android:fontFamily">sans-serif-black</item>
<item name="android:textStyle">italic</item>

具体样式如下：

image

代码中动态设置

方法1 ：只单纯设置粗体和正常

//android中为textview动态设置字体为粗体
TextView textView = (TextView)findViewById(R.id.textView);
textView .setTypeface(Typeface.defaultFromStyle(Typeface.BOLD));
//设置为不加粗
textView.setTypeface(Typeface.defaultFromStyle(Typeface.NORMAL));

方法2 ：同时搭配Fontfamily （此方法会覆盖方法1）

//android中为textview动态设置字体为粗体
TextView textView = (TextView)findViewById(R.id.textView);
//其中"sans-serif"为上面介绍的fontfamily的字符串名字，
//这个最好用一个string 资源映射，便于使用
textView .setTypeface(Typeface.create("sans-serif",Typeface.BOLD));
//同理 设置为不加粗
textView.setTypeface(Typeface.create("sans-serif-thin",Typeface.NORMAL));