Textbooks generally say simply "perfect for speech, simple past for writing," which is such an oversimplification as to really deserve being called "wrong." The generalization given here is a better reflection of reality, but it does simplify the complex reality of the living language. Beginners who enjoy details might consider the following points:

1) the simple past is generally used in spoken German that employs writerly style, such as broadcast news reports.

2) the perfect is generally used in written German that employs the style of the spoken language, such as informal letters and e-mails.

3) in some situations, the perfect is used even in formal writing to express the immediate relevance of the past events to the present. (But learners should probably not worry about this distinction until the third or fourth year.)

For more details, see Martin Durrell, Using German: A Guide to Contemporary Usage, pp. 199-200.