1. API 文档参考：http://robotium.googlecode.com/svn/doc/index.html
2. clearEditText //清除编辑框文本
a) public void clearEditText(int index)
Clears the value of an EditText.
Parameters:
index - the index of the EditText to clear. 0 if only one is available
b) public void clearEditText(android.widget.EditText editText)
Clears the value of an EditText.
Parameters:
editText - the EditText to clear