To achieve better adaptive learning for mobile-assisted language learning (MALL), individual prior knowledge proficiency, perceptual learning style, and learning behavior should all be considered in system development. While reviewing the existing literature about MALL research, the researchers of this study found very few recent studies exploring the relationship between mixed-modality learners and learning effectiveness by observing the system operating behaviors. Therefore, the researchers developed a MALL system, MyEVA Mobile, employing mixed-modality vocabulary learning, to assist students who have English as a foreign language to improve their vocabulary. To explore the effect of the system on university students with different learning attitudes and English proficiencies (English majors and non-English majors), the study used a mixed quantitative and qualitative methodology to analyze the subjects' learning achievements, perceptual learning styles, learning strategy preferences, and learning behaviors. The results of this study demonstrated how different learning behaviors varied with learners with different learning styles through diverse observations. The findings of this study are expected to provide a good reference for future MALL system development incorporating context-aware learner support as well as a direction for future researchers who wish to conduct a similar MALL study.