Android开源框架之EventBus

EventBus是一个Android端优化的publish/subscribe消息总线，简化了应用程序内各组件间、组件与后台线程间的通信。比如请求网络，等网络返回时通过Handler或Broadcast通知UI，两个Fragment之间需要通过Listener通信，这些需求都可以通过EventBus实现。其实只要是一个Java类，都能使用EventBus来完成通信。简单地说:就是可以将某个页面想要传递的信息(例如在目标页面的textview中显示“hello world!”)简便且高效率地传递给目标页面。

代码实现:

EventBusActivity

package com.atguigu.android.eventbus;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import com.atguigu.android.R;
import com.atguigu.android.eventbus.event.MessageEvent;
import com.atguigu.android.eventbus.event.StickyEvent;

import org.greenrobot.eventbus.EventBus;
import org.greenrobot.eventbus.Subscribe;
import org.greenrobot.eventbus.ThreadMode;

// eventbus
public class EventBusActivity extends Activity {
    private TextView tv_title;
    private Button bt_eventbus_send;
    private Button bt_eventbus_sticky;
    private TextView tv_eventbus_result;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_event_bus);
        
        initView();
        initData();
        initListener();
    }

    private void initListener() {
        // 跳转到发送页面
        bt_eventbus_send.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                Intent intent = new Intent(EventBusActivity.this, EventBusSendActivity.class);
                startActivity(intent);
            }
        });

        // 发送粘性事件到发送页面
        bt_eventbus_sticky.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // 2 发送粘性事件
                EventBus.getDefault().postSticky(new StickyEvent("我是粘性事件"));
                // 跳转到发送数据页面
                Intent intent = new Intent(EventBusActivity.this, EventBusSendActivity.class);
                startActivity(intent);
            }
        });
    }

    private void initData() {
        tv_title.setText("EventBus");
        // 1注册广播
        EventBus.getDefault().register(EventBusActivity.this);
    }

    private void initView() {
        tv_title = (TextView)findViewById(R.id.tv_title);

        bt_eventbus_send = (Button)findViewById(R.id.bt_eventbus_send);
        bt_eventbus_sticky = (Button)findViewById(R.id.bt_eventbus_sticky);
        tv_eventbus_result = (TextView)findViewById(R.id.tv_eventbus_result);
    }

    // 5接收消息
    @Subscribe(threadMode = ThreadMode.MAIN)
    public void MesssageEventBus(MessageEvent event){

        // 显示接收的消息
        tv_eventbus_result.setText(event.name);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();

        // 2 解注册
        EventBus.getDefault().unregister(EventBusActivity.this);
    }
}

EventBusSendActivity

package com.atguigu.android.eventbus;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import com.atguigu.android.R;
import com.atguigu.android.eventbus.event.MessageEvent;
import com.atguigu.android.eventbus.event.StickyEvent;

import org.greenrobot.eventbus.EventBus;
import org.greenrobot.eventbus.Subscribe;
import org.greenrobot.eventbus.ThreadMode;

// eventbus的发送数据页面
public class EventBusSendActivity extends Activity {
    private TextView tv_title;
    private Button bt_eventbus_send_main;
    private Button bt_eventbus_send_sticky;
    private TextView tv_eventbus_send_result;

    boolean isFirstFlag = true;

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

        initView();
        initData();
        initListener();
    }

    private void initListener() {
        // 主线程发送数据按钮点击事件处理
        bt_eventbus_send_main.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // 4 发送消息
                EventBus.getDefault().post(new MessageEvent("主线程发送过来的数据"));
                //post方法发送给的是在这之前已经register的的所有activity，若晚于post方法regsiter的activity则不会接收到数据
                // 结束当前页面
                finish();
            }
        });

        // 接收粘性事件数据按钮的点击事件处理
        bt_eventbus_send_sticky.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                if(isFirstFlag) {
                    isFirstFlag = false;
                    // 4 注册
                    EventBus.getDefault().register(EventBusSendActivity.this);//粘性事件就是在注册之前已经post了，但是依然可以获取到该事件。
                }
            }
        });
    }

    // 3 接收粘性事件
    @Subscribe(threadMode = ThreadMode.MAIN, sticky = true)
    public void StickyEventBus(StickyEvent event){
        // 显示接收的数据
        tv_eventbus_send_result.setText(event.msg);
    }

    private void initData() {
        tv_title.setText("EventBus发送数据页面");
    }

    private void initView() {
        tv_title = (TextView)findViewById(R.id.tv_title);
        bt_eventbus_send_main = (Button)findViewById(R.id.bt_eventbus_send_main);
        bt_eventbus_send_sticky = (Button)findViewById(R.id.bt_eventbus_send_sticky);
        tv_eventbus_send_result = (TextView)findViewById(R.id.tv_eventbus_send_result);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();

        // 5 解注册
        EventBus.getDefault().removeAllStickyEvents();
        EventBus.getDefault().unregister(EventBusSendActivity.this);
    }
}

MessageEvent

package com.atguigu.android.eventbus.event;

// 3 创建发送消息类
public class MessageEvent {
    public String name;
    public MessageEvent(String name) {
        this.name = name;
    }
}

StickyEvent

package com.atguigu.android.eventbus.event;

// 1创建一个粘性事件类
public class StickyEvent {
    public String msg;
    public StickyEvent(String msg) {
        this.msg = msg;
    }
}

总结: