尝试使用 proguard 创建安全 apk 时，出现以下错误：
Proguard returned with error code 1. See console
[2013-10-19 09:04:44 - TeacherBook] Warning: com.dafruits.android.library.widgets.ExtendedListView: can't find referenced class com.dafruits.android.library.R$styleable
[2013-10-19 09:04:44 - TeacherBook] Warning: com.dafruits.android.library.widgets.ExtendedListView: can't find referenced class com.dafruits.android.library.R$styleable
[2013-10-19 09:04:44 - TeacherBook] Warning: com.dafruits.android.library.widgets.ExtendedListView: can't find referenced class com.dafruits.android.library.R$anim
[2013-10-19 09:04:44 - TeacherBook] Warning: com.dafruits.android.library.widgets.ExtendedListView: can't find referenced class com.dafruits.android.library.R$anim
[2013-10-19 09:04:44 - TeacherBook] Warning: com.dafruits.android.library.widgets.ExtendedListView: can't find referenced class com.dafruits.android.library.R$anim
[2013-10-19 09:04:44 - TeacherBook] Warning: com.dafruits.android.library.widgets.ExtendedListView: can't find referenced class com.dafruits.android.library.R
[2013-10-19 09:04:44 - TeacherBook] Warning: there were 6 unresolved references to classes or interfaces.
[2013-10-19 09:04:44 - TeacherBook] You may need to add missing library jars or update their versions.
[2013-10-19 09:04:44 - TeacherBook] If your code works fine without the missing classes, you can suppress
[2013-10-19 09:04:44 - TeacherBook] the warnings with '-dontwarn' options.
[2013-10-19 09:04:44 - TeacherBook] (http://proguard.sourceforge.net/manual/troubleshooting.html#unresolvedclass)
[2013-10-19 09:04:44 - TeacherBook] java.io.IOException: Please correct the above warnings first.
[2013-10-19 09:04:44 - TeacherBook] at proguard.Initializer.execute(Initializer.java:369)
[2013-10-19 09:04:44 - TeacherBook] at proguard.ProGuard.initialize(ProGuard.java:212)
[2013-10-19 09:04:44 - TeacherBook] at proguard.ProGuard.execute(ProGuard.java:87)
[2013-10-19 09:04:44 - TeacherBook] at proguard.ProGuard.main(ProGuard.java:484)