09-09 09:42:48.892: ERROR/dalvikvm(300): Could not find method java.lang.String.isEmpty, referenced from method org.scribe.utils.Preconditions.check
09-09 09:42:48.902: WARN/dalvikvm(300): VFY: unable to resolve virtual method 22: Ljava/lang/String;.isEmpty ()Z
09-09 09:42:48.902: WARN/dalvikvm(300): VFY: rejecting opcode 0x6e at 0x0006
09-09 09:42:48.902: WARN/dalvikvm(300): VFY: rejected Lorg/scribe/utils/Preconditions;.check (ZLjava/lang/String;)V
09-09 09:42:48.902: WARN/dalvikvm(300): Verifier rejected class Lorg/scribe/utils/Preconditions;
09-09 09:42:48.902: DEBUG/AndroidRuntime(300): Shutting down VM
09-09 09:42:48.902: WARN/dalvikvm(300): threadid=3: thread exiting with uncaught exception (group=0x4001aa28)
09-09 09:42:48.912: ERROR/AndroidRuntime(300): Uncaught handler: thread main exiting due to uncaught exception
09-09 09:42:48.922: ERROR/AndroidRuntime(300): java.lang.VerifyError: org.scribe.utils.Preconditions
09-09 09:42:48.922: ERROR/AndroidRuntime(300): at org.scribe.builder.ServiceBuilder.createApi(ServiceBuilder.java:43)
09-09 09:42:48.922: ERROR/AndroidRuntime(300): at org.scribe.builder.ServiceBuilder.provider(ServiceBuilder.java:37)

there is no isEmpty() method in java.lang.String class
trim().equals("") is fine.