1、下面是EventBus3.0的一些用法和源码分析
2、接下来自己实现EventBus的一些简单功能
定义一个EventBus类,主要实现register和post连个方法
public class EventBus {
private static volatile EventBus instace;
private Map> eventTypesCache = new HashMap<>();
private EventBus(){
}
public static EventBus getDefault(){
if(instace == null){
synchronized (EventBus.class){
if(instace == null)
instace = new EventBus();
}
}
return instace;
}
public void register(Object subscriber){
List subscribleMethods = eventTypesCache.get(subscriber);
if(subscribleMethods == null){
subscribleMethods = findSubscriberMethods(subscriber);
eventTypesCache.put(subscriber,subscribleMethods);
}
}
private List findSubscriberMethods(Object subscriber) {
/**
* 线程安全
*/
List subscribleMethods = new CopyOnWriteArrayList<>();
Class clazz = subscriber.getClass();
Method[] methods = clazz.getDeclaredMethods();
//循环查找父类的接受方法
while (clazz != null){
String name = clazz.getName();
if (name.startsWith("java.") || name.startsWith("javax.") || name.startsWith("android.")) {
break;
}
for(Method method : methods){
Subscribe subscribe = method.getAnnotation(Subscribe.class);//拿到方法上的注解
if(subscribe == null){
continue;
}
//拿到方法的参数数组
Class[] parameterTypes = method.getParameterTypes();
if(parameterTypes.length != 1)//如果方法中的参数不是一个，就抛错
throw new RuntimeException("eventBus must be one parameter!");
Class parameterType = parameterTypes[0];
ThreadMode threadMode = subscribe.value();
SubscribleMethod subscribleMethod = new SubscribleMethod(method,threadMode,parameterType);
subscribleMethods.add(subscribleMethod);
}
clazz = clazz.getSuperclass();
}
return subscribleMethods;
}
public void post(Object event){
Set 实现SubscribleMethod类，管理EventBus接受方法的一些属性,方法名、注解、参数
public class SubscribleMethod {
private Method method;//方法
private ThreadMode threadMode;//这个方法所在那个线程
private Class eventType;//参数类型
public SubscribleMethod(Method method, ThreadMode threadMode, Class eventType) {
this.method = method;
this.threadMode = threadMode;
this.eventType = eventType;
}
public Method getMethod() {
return method;
}
public void setMethod(Method method) {
this.method = method;
}
public ThreadMode getThreadMode() {
return threadMode;
}
public void setThreadMode(ThreadMode threadMode) {
this.threadMode = threadMode;
}
public Class getEventType() {
return eventType;
}
public void setEventType(Class eventType) {
this.eventType = eventType;
}
}
定义一个ThreadMode枚举类主要是管理EventBus运行在线程的环境
public enum ThreadMode {
PostThread,
}
定义一个Subscribe注解类
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface Subscribe {
ThreadMode value() default ThreadMode.PostThread;
}
以上自己定义的EventBus已经完成简单的传递事件功能，
3、下面是使用自定义的EventBus
定义传递事件对象User
public class User {
private String name;
private int age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
在第一个页面MainActivity中定义接受事件
@Subscribe
public void receive(User user){
tv.setText("姓名："+user.getName()+",年龄："+user.getAge());
}
在第二个页面发送事件
public void onSendDataClick(View view){
User user = new User();
user.setName("张三");
user.setAge(20);
EventBus.getDefault().post(user);
finish();
}
4、事件的效果如下：
EventBus.gif
5、接下来实现EventBus传递和接收事件的线程切换
在ThreadMode中添加几个枚举
public enum ThreadMode {
PostThread,
MainThread,
BackgroundThread,
}
在添加一个Handler和一个ExecutorService线程池的实例
private Handler handler;
private ExecutorService executorService;
private EventBus(){
handler = new Handler(Looper.getMainLooper());
executorService = Executors.newCachedThreadPool();
}
然后修改EventBus类的post方法
public void post(final Object event){
Set最后在修改MainActivity中的接收事件注解
@Subscribe(ThreadMode.BackgroundThread)
public void receive(User user){
Log.e("zxj","Thread name:"+Thread.currentThread().getName());
tv.setText("姓名："+user.getName()+",年龄："+user.getAge());
}
ThreadMode的枚举是那个就对应在那个线程中
指定为MainThread时表示是在主线程，指定为BackgroundThread时表示是在子线程，当指定为PostThread(默认)时表示，发送事件(调用post方法)时，post在那个线程，接受就在那个线程
如下图当ThreadMode.BackgroundThread时：
6、最后在提供一个取消注册的方法,在MainActivity的onDestroy方法中调用
public void unregister(Object subscriber) {
if (subscriber != null)
eventTypesCache.remove(subscriber);
}