本版本为1.0，支持较少，使用不够方便。相关封装逻辑结构已升级至2.0，详情可参见：更完善的安卓事件监听实现
先简单扯两句这几天学习下来对java事件监听机制的一点感触。客观地讲，java的事件监听机制相比.net好原始，暂不说委托、lamda、泛型、反射等的繁琐，仅一个事件监听，就需要各种listener才能实现，比如安卓里到处都是view.setOnXXXXListener。被C#“语法糖”和宇宙第一IDE惯坏的我真心有点不习惯，于是就决定写个工具来封装这些烦人的listener。开始切入正题。
摆脱安卓里各种listener的繁琐，像写一般的方法似的写各种事件。
二、成果
只要写一个类(这里以MainActivityEvent命名的类为例)继承EventManager，然后在对应的MainActivity里的onCreate方法里初始化这个类(new MainActivityEvent(this))即可完成注册。剩下的就只需要在MainActivityEvent类里写对应的事件响应逻辑就可以了。
三、实现概况
3.1 MainActivity里注册。
3.2 MainActivityEvent的实现。
3.3 封装的相关类型。
四、具体实现及代码
4.1 EventType.java
package com.example.personal.events; /**
* Event type.
*/
public enum EventType {
/**
* signature: (View v, int keyCode, KeyEvent event)
* return: boolean.
*/
OnKey,
/**
* signature: (View v, MotionEvent event)
* return: boolean.
*/
OnTouch,
/**
* signature: (View v, MotionEvent event)
* return: boolean.
*/
OnHover,
/**
* signature: (View v, MotionEvent event)
* return: boolean.
*/
OnGenericMotion,
/**
* signature: (View v)
* return: boolean.
*/
OnLongClick,
/**
* signature: (View v, DragEvent event)
* return: boolean.
*/
OnDrag,
/**
* signature: (View v, boolean hasFocus)
* return: void.
*/
OnFocusChange,
/**
* signature: (View v)
* return: void.
*/
OnClick,
/**
* signature: (ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo)
* return: void.
*/
OnCreateContextMenu, //TODO: Not supported for api version issues or other special reasons.
// /**
// * signature: (View v)
// */
// OnViewAttachedToWindow,
// /**
// * signature: (View v)
// */
// OnViewDetachedFromWindow,
// /**
// * signature: (View v)
// */
// OnContextClick,
// /**
// * signature: (int visibility)
// */
// OnSystemUiVisibilityChange
}
4.2 EventAnnotation.java
package com.example.personal.events; import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target; @Documented
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface EventAnnotation {
/**
* View id.
*
* @return the view id that the event binds to.
*/
int value(); /**
* Event type. If not specified, onClick will be set by default.
*
* @return the event type of the method binds to.
*/
EventType eventType() default EventType.OnClick;
}
4.3 EventManager.java
package com.example.personal.events; import android.app.Activity;
import android.view.ContextMenu;
import android.view.DragEvent;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.View; import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map; /**
* A abstract class to encapsulate most of the view event listeners. When bind an event to a view, in derived class,
* you just need to declare a method that same with the event's signature, and annotate with {@link EventAnnotation}.
* Note: the return value match is not required but recommended. For method that requires return boolean type,
* {@code true} will be returned by default if the method return type is not.
*/
public abstract class EventManager
implements
View.OnKeyListener,
View.OnTouchListener,
View.OnHoverListener,
View.OnGenericMotionListener,
View.OnLongClickListener,
View.OnDragListener,
View.OnFocusChangeListener,
View.OnClickListener,
View.OnCreateContextMenuListener { private final Map<Integer, Map<EventType, Method>> eventMap;
protected final Activity activity; protected EventManager(Activity activity) {
this.activity = activity;
eventMap = new HashMap<>();
registerEvents();
} private void setListener(View view, EventType eventType) {
switch (eventType) {
case OnKey:
view.setOnKeyListener(this);
break;
case OnTouch:
view.setOnTouchListener(this);
break;
case OnHover:
view.setOnHoverListener(this);
break;
case OnGenericMotion:
view.setOnGenericMotionListener(this);
break;
case OnLongClick:
view.setOnLongClickListener(this);
break;
case OnDrag:
view.setOnDragListener(this);
break;
case OnFocusChange:
view.setOnFocusChangeListener(this);
break;
case OnClick:
view.setOnClickListener(this);
break;
case OnCreateContextMenu:
view.setOnCreateContextMenuListener(this);
break;
}
} private void registerEvents() {
for (Method method : this.getClass().getDeclaredMethods()) {
if (method.isAnnotationPresent(EventAnnotation.class)) {
EventAnnotation annotation = method.getAnnotation(EventAnnotation.class);
int viewId = annotation.value();
View view = activity.findViewById(viewId);
if (view != null) {
method.setAccessible(true);
EventType eventType = annotation.eventType();
setListener(view, eventType);
Map<EventType, Method> actionMap;
if (eventMap.containsKey(viewId)) {
actionMap = eventMap.get(viewId);
actionMap.put(eventType, method);
} else {
actionMap = new HashMap<>();
actionMap.put(eventType, method);
eventMap.put(viewId, actionMap);
}
}
}
}
} private Object invokeAction(EventType eventType, Object... args) {
View view = null;
for (Object obj : args) {
if (obj instanceof View) {
view = (View) obj;
break;
}
} if (view == null) {
return null;
} Method action = eventMap.get(view.getId()).get(eventType);
Object result = null;
if (action != null) {
try {
result = action.invoke(this, args);
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
} return result;
} private boolean invokeActionReturnStatus(EventType eventType, Object... args) {
Object result = invokeAction(eventType, args);
return result instanceof Boolean ? true : (boolean) result;
} @Override
public void onClick(View v) {
invokeAction(EventType.OnClick, v);
} @Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
invokeAction(EventType.OnCreateContextMenu, menu, v, menuInfo);
} @Override
public boolean onDrag(View v, DragEvent event) {
return invokeActionReturnStatus(EventType.OnDrag, v, event);
} @Override
public void onFocusChange(View v, boolean hasFocus) {
invokeAction(EventType.OnFocusChange, v, hasFocus);
} @Override
public boolean onGenericMotion(View v, MotionEvent event) {
return invokeActionReturnStatus(EventType.OnGenericMotion, v, event);
} @Override
public boolean onHover(View v, MotionEvent event) {
return invokeActionReturnStatus(EventType.OnHover, v, event);
} @Override
public boolean onKey(View v, int keyCode, KeyEvent event) {
return invokeActionReturnStatus(EventType.OnKey, v, keyCode, event);
} @Override
public boolean onLongClick(View v) {
return invokeActionReturnStatus(EventType.OnLongClick, v);
} @Override
public boolean onTouch(View v, MotionEvent event) {
return invokeActionReturnStatus(EventType.OnTouch, v, event);
}
}
五、总结
源码下载：code.rar
为了减少重复实现listener接口的繁琐，自己写了点api以便使用。谨以此做一下记录和分享，如有问题，欢迎斧正，如果建议，欢迎反馈，此谢！