Abstract

Design patterns add more reliability, flexibility and reusability to a software system. Taking advantage of design patterns is usually beneficial to software design and makes software development relatively easier. The state pattern proposed by GoF is not a determined design and can hardly be transformed into implementation code directly. It is disable to cope with sophisticated response event either. Hereby we propose a novel event-conditionstate pattern framework, an event-based finite state machine. The framework improves GoF state pattern by resegmenting Context into two classes, one for management and the other for operation interface. Essential components for implementation, such as management, state transferring, and event triggering mechanism, are also taken into consideration in the framework. We use pattern framework to develop a thirty party input method system which has a Windows Mobile system version and a Symbian system version separately. We rewrote Context part related with system interfaces in the two different systems, and encapsulated the part related with internal logic of input method by concrete subclasses, thus avoiding redundant developing work in both systems and providing convenience for later synchronous updating and maintenance of two input methods. With the pattern framework, much effort during software development is saved. The development logic seems simpler and clearer. As a result, the whole development process is simplified.