Eventbus简单使用

EventBus是一款针对Android优化的发布/订阅事件总线。主要功能是替代Intent,Handler,BroadCast在Fragment，Activity，Service，线程之间传递消息.优点是开销小，代码更优雅。以及将发送者和接收者解耦。

话不多说，直接上代码：

用于接收信息的Activity：

package com.lucasey.eventbus;

import de.greenrobot.event.EventBus;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends Activity {

    private Button btn;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //注册EventBus
        EventBus.getDefault().register(this);
        btn = (Button) findViewById(R.id.FristBtn);
        btn.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(MainActivity.this,SecondActivity.class);
                startActivity(intent);
            }
        });
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        //反注册
        EventBus.getDefault().unregister(this);
    }

    public void onEventMainThread(FristEvent event){
        String msg = "我收到消息:"+event.getMsg();
        Log.e("TAG", msg    );
        Toast.makeText(MainActivity.this, msg, 1);
        btn.setText(msg);
    }

}

对应布局：

<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <Button
        android:id="@+id/FristBtn"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="首页activity" />

</RelativeLayout>

发送消息的Activity：

package com.lucasey.eventbus;

import de.greenrobot.event.EventBus;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;


public class SecondActivity extends Activity{

    private Button btn;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);
        btn = (Button) findViewById(R.id.SecondBtn);
        btn.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                EventBus.getDefault().post(new FristEvent("警察来抓你了\t快跑"));
                SecondActivity.this.finish();
            }
        });
    }
}

对应XML：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin" >

    <Button
        android:id="@+id/SecondBtn"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="SecondActivity" />

</LinearLayout>

除了在activity中注册与反注册，另外还要定义一个消息类，用于传递消息，并且构造方法传入消息，getMsg()取出：

package com.lucasey.eventbus;

public class FristEvent {

    private String msg;

    public FristEvent(String msg){
        this.msg = msg;
    }

    public String getMsg(){
        return this.msg;
    }

}

也就说，在需要接收消息的activity中注册eventbus：EventBus.getDefault().register(this);
定义onEventMainThread(FristEvent event)方法来接收消息。而在需要发送消息的activity中，
通过EventBus.getDefault().post(new FristEvent("Message"));将消息发送出去；