EventBus 学习

一.概述

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。

实现主要有3个元素组成
1.事件：event
2.发布者：发出消息的一方
3.订阅者：接受并处理消息

二.使用步骤

1.下载EventBus库

地址：https://github.com/greenrobot/EventBus
1.添加gradle
compile 'de.greenrobot:eventbus:2.4.0'
2.下载库，解压，在项目中import modules,再设置dependence

2.自定义事件类

public class TestEvent {    private String mMesg;    public TestEvent(String mMesg) {        this.mMesg = mMesg;    }    public String getmMesg() {        return mMesg;    }}

3.订阅者注册以及取消注册

注册：EventBus.getDefault().register(this);取消：EventBus.getDefault().unregister(this);

4.发布者发送消息

EventBus.getDefault().post(new TestEvent("send mesg"));

5.订阅者消息处理

public void onEventMainThread()

三、实践

在MainActivity中点击button跳转至SecondActivity，在SecondActivity中点击button发送消息给MainActivity,并跳转至MainActivity，MainActivity处理实践，并且显示。

1.MainActivity布局

<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:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    android:orientation="vertical"    tools:context=".MainActivity">    <TextView        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="@string/FirstActivity" />    <TextView        android:id="@+id/display_mesg"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:textSize="20sp"        android:background="#00ff00"        android:visibility="gone"/>    <Button        android:id="@+id/start_activity"        android:text="@string/start_activity"        android:layout_width="match_parent"        android:layout_height="wrap_content" /></LinearLayout>

2.SecondActivity布局

<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:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    android:orientation="vertical"    tools:context="com.example.xuyushi.eventbustest.SecondActivity">    <TextView        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="@string/SecondActivity" />    <Button        android:id="@+id/send_mesg"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="@string/sendMesg"/></LinearLayout>

3.自定义Event

package com.example.xuyushi.eventbustest;/** * Created by xuyushi on 15/6/14. */public class TestEvent {    private String mMesg;    public TestEvent(String mMesg) {        this.mMesg = mMesg;    }    public String getmMesg() {        return mMesg;    }}

4.MainAcitivity 按键事件

        button.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent intent = new Intent(getApplicationContext(), SecondActivity.class);                startActivity(intent);            }        });

5.SecondActivity 按键事件

        button.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                //send mesg to MainActivity                EventBus.getDefault().post(new TestEvent("send mesg"));                Toast.makeText(getApplicationContext(),"mesg have send",Toast.LENGTH_SHORT).show();                finish();            }        });

6.处理事件

    public void onEventMainThread(TestEvent testEvent) {        String msg = testEvent.getmMesg();        Log.d("MainActivity", "msg have recevied:" + msg);        displayMesg.setText("msg have recevied:"+ msg);        displayMesg.setVisibility(View.VISIBLE);    }

源码：https://github.com/xuyushi/EventBusTest