android - 事件的 Otto 事件总线运行时订阅

Question

是否可以在 Otto 中订阅事件而不使用 @Subscribe 注释？

在我的用例中，我不知道我的对象应该在编译时订阅哪个事件。我希望根据某些规则在运行时执行此操作。

Answer 1

我想你可以使用这样的解决方法，

public class MainClass {    

    private EventObserver eventObserver;

    public MainClass() {
        if(...someCondition...) {
            eventObserver = new FirstEventObserver();
        } else {
            eventObserver = new SecondEventObserver();
        }
    }

    public onEvent(Event event) {
        if (event instanceOf FirstEvent) {
            ... handle event ...
        } else if (event instanceOf SecondEvent) {
            ... handle event ...
        }
    }
}

public abstract class EventObserver {

    protected MainClass mainClass;

    public void setMainClass(MainClass mainClass) {
        this.mainClass = mainClass;
    }

    protected void notifyMainClass(Event event) {
        if (mainClass != null) {
            mainClass.onEvent(event);
        }
    }
}

public class FirstEventObserver extends EventObserver {

    public FirstEventObserver() {
        bus.subscribe(this);
    }

    @Subscribe
    public void onEvent(FirstEvent event) {
        notifyMainClass();
    }
}


public class SecondEventObserver extends EventObserver {

    public SecondEventObserver() {
        bus.subscribe(this);
    }

    @Subscribe
    public void onEvent(SecondEvent event) {
        notifyMainClass();
    }
}

public abstract class Event {
}

public abstract class FirstEvent extends Event {
}

public abstract class SecondEvent extends Event {
}

另一种解决方法，这是一种更简洁的解决方案。您可以在运行时生成所需类型的事件。

public class MainClass {
    @Subscribe
    public void onEvent(Event event) {
        if (event.getType() == EventType.FIRST_EVENT) {
            ... handle event ...
        } else if (event.getType() == EventType.SECOND_EVENT) {
            ... handle event ...
        }
    }
}

public class Event {
    public enum EventType {
        FIRST_EVENT,
        SECOND_EVENT
    }

    private EventType eventType;

    public Event(EventType eventType) {
        this.eventType = eventType;
    }

    public EventType getType() {
        return eventType;
    }
}