android – google-api-java-client NetHttpTransport导致NoClassDefFoundError

我刚开始在 Android上学习google-api-java-client.
将下3个库添加到项目中. (我不使用Maven.)

> google-api-client-1.4.1-beta.jar
> google-api-client-googleapis-1.4.1-beta.jar
> google-api-client-googleapis-extensions-andr

并选择了可供使用的示例代码.在示例中,它使用了GoogleTransport,现在似乎无法使用.

httpTransport transport = GoogleTransport.create();

所以我把它改成了在网上找到的NethttpTransport().

import com.google.api.client.http.javanet.NethttpTransport;
...
   httpTransport transport = new NethttpTransport();

但是,我得到了例外.

05-24 15:54:33.310: ERROR/AndroidRuntime(4586): java.lang.NoClassDefFoundError: com.google.common.base.Preconditions
05-24 15:54:33.310: ERROR/AndroidRuntime(4586):     at com.google.api.client.util.ClassInfo.<init>(ClassInfo.java:324)
05-24 15:54:33.310: ERROR/AndroidRuntime(4586):     at com.google.api.client.util.ClassInfo.of(ClassInfo.java:77)
05-24 15:54:33.310: ERROR/AndroidRuntime(4586):     at com.google.api.client.util.GenericData.<init>(GenericData.java:44)
05-24 15:54:33.310: ERROR/AndroidRuntime(4586):     at com.google.api.client.http.httpHeaders.<init>(httpHeaders.java:37)
05-24 15:54:33.310: ERROR/AndroidRuntime(4586):     at com.google.api.client.http.httpTransport.<init>(httpTransport.java:82)
05-24 15:54:33.310: ERROR/AndroidRuntime(4586):     at com.google.api.client.http.javanet.NethttpTransport.<init>(NethttpTransport.java:35)
05-24 15:54:33.310: ERROR/AndroidRuntime(4586):     at net.DailyTimer.test.MainActivity.onCreate(MainActivity.java:290)

这有什么问题？