android中EventBus总线框架的使用

android中用于解耦的框架有EventBus，Otto,Rx系列。

本章先来说说对EventBus的使用。

引用一个图片：

EventBus使用分为3步：

1.定义event事件，就是一个自定义的类，类的作用要能用来携带数据和区分事件类型。

public class MessageEvent {
public final String message;
public int eventType;

public MessageEvent(String message,int eventType) {
this.message = message;
this.eventType = eventType;
}
}

2.订阅事件：

注册和注销总线，

@Override
public void onStart() {
super.onStart();
EventBus.getDefault().register(this);
}

@Override
public void onStop() {
EventBus.getDefault().unregister(this);
super.onStop();
}

接收发布结果

// This method will be called when a MessageEvent is posted (in the UI thread for Toast)
@Subscribe(threadMode = ThreadMode.MAIN)
public void onMessageEvent(MessageEvent event) {
Toast.makeText(getActivity(), event.message, Toast.LENGTH_SHORT).show();
}

3.发布事件：

所有注册了该事件的订阅者都会收到该事件

EventBus.getDefault().post(new MessageEvent("Hello everyone!"));

事件接收后，可以选择在哪个线程模型中使用：

1.ThreadMode: POSTING

2 ThreadMode: MAIN

3 ThreadMode: BACKGROUND

4 ThreadMode: ASYNC

@Subscribe(threadMode = ThreadMode.POSTING) // ThreadMode is optional here
public void onMessage(MessageEvent event) {
log(event.message);
}
与post处于同一线程，是默认的处理模型。

// Called in Android UI's main thread
@Subscribe(threadMode = ThreadMode.MAIN)
public void onMessage(MessageEvent event) {
textField.setText(event.message);
}
主线程中处理，更新Ui

// Called in the background thread
@Subscribe(threadMode = ThreadMode.BACKGROUND)
public void onMessage(MessageEvent event){
saveToDisk(event.message);
}
如果发布事件是在主线程，那么这里的执行就在子线程；如果发布事件是在子线程，那么这里执行所在的线程与发布所在线程处于同一个线程。

// Called in a separate thread
@Subscribe(threadMode = ThreadMode.ASYNC)
public void onMessage(MessageEvent event){
backend.send(event.message);
}
另起一个线程来处理。

4.一个小例子：

运行截图：

说明了在发布事件处于UI和子线程情况下，使用不同的线程模型接收事件的结果；

发布事件在主线程的情况：



发布事件在子线程的情况：



具体代码如下：

所有事件的基类：其他事件继承该类；

<span style="font-size:14px;">public class BaseEvent {
private int eventType;

public BaseEvent(int eventType) {
super();
this.eventType = eventType;
}

public int getEventType() {
return eventType;
}

public void postEvent() {
EventBus.getDefault().post(this);
}

}</span>

所有的事件类型定义：用一个整形值来区分不同事件

<span style="font-size:14px;">public interface EventType {
public static final int CONSTANT = 1;
public static final int EVENT_TYPE_SENDMSG = CONSTANT << 1;
}</span>

自定义的一个事件类型：

<span style="font-size:14px;">public class SendMsgEvent extends BaseEvent {

public SendMsgEvent(int eventType) {
super(eventType);
}

public String msg;

}</span>

MainActivity.java

<span style="font-size:14px;">public class MainActivity extends Activity {

private TextView tv_async;
private TextView tv_background;
private TextView tv_main;
private TextView tv_post;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

// EventBus注册，订阅事件
EventBus.getDefault().register(this);

tv_async = (TextView) findViewById(R.id.tv_async);
tv_background = (TextView) findViewById(R.id.tv_background);
tv_main = (TextView) findViewById(R.id.tv_main);
tv_post = (TextView) findViewById(R.id.tv_post);

findViewById(R.id.bt_main).setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// 发布事件
sendMsg();
}
});

findViewById(R.id.bt_sub).setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// 发布事件
new Thread() {
public void run() {
sendMsg();
};
}.start();

}
});
}

// 处理订阅的事件，android中常用这个，方法名任意只要有注解就行
@Subscribe(threadMode = ThreadMode.MAIN)
public void onMessage_Main(BaseEvent event) {
switch (event.getEventType()) {
case EventType.EVENT_TYPE_SENDMSG:
SendMsgEvent sendMsgEvent = (SendMsgEvent) event;
disText(tv_main,sendMsgEvent.msg);
break;
}
}

@Subscribe(threadMode = ThreadMode.ASYNC)
public void onMessage_Async(BaseEvent event) {
switch (event.getEventType()) {
case EventType.EVENT_TYPE_SENDMSG:
SendMsgEvent sendMsgEvent = (SendMsgEvent) event;
disText(tv_async,sendMsgEvent.msg);
break;
}
}

@Subscribe(threadMode = ThreadMode.POSTING)
public void onMessage_Post(BaseEvent event) {
switch (event.getEventType()) {
case EventType.EVENT_TYPE_SENDMSG:
SendMsgEvent sendMsgEvent = (SendMsgEvent) event;
disText(tv_post,sendMsgEvent.msg);
break;
}
}

@Subscribe(threadMode = ThreadMode.BACKGROUND)
public void onMessage_Background(BaseEvent event) {
switch (event.getEventType()) {
case EventType.EVENT_TYPE_SENDMSG:
SendMsgEvent sendMsgEvent = (SendMsgEvent) event;
disText(tv_background,sendMsgEvent.msg);
break;
}
}

private void disText(final TextView tv, final String msg) {
final String processThread = Thread.currentThread().getName();
tv.post(new Runnable() {
@Override
public void run() {
tv.setText(msg+"\n process event in "+processThread);
}
});
}

private void sendMsg() {
SendMsgEvent sendMsgEvent = new SendMsgEvent(
EventType.EVENT_TYPE_SENDMSG);
sendMsgEvent.msg = "post event in " + Thread.currentThread().getName();
sendMsgEvent.postEvent();
}

@Override
protected void onDestroy() {
super.onDestroy();
// EventBus注销，取消订阅事件
EventBus.getDefault().unregister(this);
}
}</span>

activity_main.xml

<span style="font-size:14px;"><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="${relativePackage}.${activityClass}" >

<Button
android:id="@+id/bt_main"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:text="send in maintThread" />

<Button
android:id="@+id/bt_sub"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:text="send in subThread" />

<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:text="result:\nmain\npost\nasync\nbackground" />

<TextView
android:id="@+id/tv_main"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:text="result" />

<TextView
android:id="@+id/tv_post"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:text="result" />

<TextView
android:id="@+id/tv_async"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:text="result" />

<TextView
android:id="@+id/tv_background"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:text="result" />

</LinearLayout></span>