【转】手机制式的解释

Preferred Network Types change the type of frequency the phone searches for.
Android is used on several devices that can gain access to different cell carriers. The 'Testing' menu that contains the 'preferred network types' you are referring you to is used for all of those Android devices as far as I can tell. 

For simplicity, there are two main types of cell carriers, GSM and CDMA.
The following popular data communication technology is associated with each cell carrier type:
GSM = GPRS (2g), EDGE(2g), UMTS(3g), WCDMA(3g), HSDPA(3g) {Cell Carrier examples: AT&T and T-Mobile}
CDMA = CDMA*(2/3g) EV-DO(3g) WiMax(3/4g) {Cell Carrier examples: Verizon and Sprint}

Now that the general stuff is out of the way, here's my take on the Preferred Network types:

WCDMA preferred - The GSM phone is capable of using both 2G and 3G data communication and when signal strength is low 3G is favored more.
GSM only - The GSM phone is capable of using only 2G data communication. When the 2G signal is too low you get nothing at all.
WCDMA only - The GSM phone is capable of using only 3G data communication. When the 3G signal is too low you get nothing at all.
GSM auto (PRL) - The GSM phone is capable of using both 2G and 3G data communication and when signal strength is low 2G is favored more. This one is a bit confusing to me since PRL is associated mostly with CDMA technology and not GSM technology.
CDMA auto (PRL) - The CDMA phone is capable of using both 2G and 3G data communication and when signal strength is low 2G is favored more.
CDMA only - The CDMA phone is capable of using only 2G data communication. When the 2G signal is too low you get nothing at all.
EvDo only - The CDMA phone is capable of using only 3G data communication. When the 3G signal is too low you get nothing at all.
GSM/CDMA auto (PRL) - Some phones are equipped with both GSM and CDMA capabilities. This setting appears to just have the phone attempt to stay connected to the data communication type that works the best. (Maybe the Samsung Galaxy S will take advantage of this???)
Unknown - If none of the above fit or the phone is acting weird as far as connecting to the carrier, you will see your preferred network type is set to this

When using the 'only' options you should still be able to make calls.

To put things into perspective, The Nexus One is set to WCDMA preferred as default and the Droid Incredible is set to CDMA auto (PRL).

Some References:
http://www.google.com/support/forum/p/android/thread?tid=34f1f0c3bc7affe1&hl=en
http://en.wikipedia.org/wiki/3G
http://en.wikipedia.org/wiki/Preferred_Roaming_List
http://ncare.com/2010/03/29/how-to-update-your-phones-with-the-newest-towers/

关于declare-styleable

见http://stackoverflow.com/questions/3441396/defining-custom-attrs

ERROR: In XXX, unable to find attribute yyy

Android 中定义declare-styleable时碰到这个错误，折腾了3个小时，才发现是<attr>这个tag只写了name，而没有写format。。。

正确的写法是

<attr name="some name" format="string" />

[转]如何忽略Android资源编译错误 Error: this attribute must be localized.

http://blog.csdn.net/forlong401/article/details/7218204

这个错误是由于强制要求应用程序按照多国语言的模式开发，避免死的字符串。

但有的时候你发现导入别人的代码，改这些字符串太麻烦，那么可以在Android.mk中添加

LOCAL_MODULE_TAGS := tests