EventBus全面讲解和案例

EventBus(https://github.com/greenrobot/EventBus)

EventBus is a publish/subscribe event bus optimized for Android.(EventBus是Android的发布/订阅事件总线优化。)

 

1.simplifies the communication between components(简化了组件之间的通信)

（1）decouples event senders and receivers(将事件发送者和接受者解耦)

（2）performs well with Activities, Fragments, and background threads(很好的执行活动、碎片和后台线程)

（3）avoids complex and error-prone dependencies and life cycle issues(避免了复杂的和容易出错的依赖性和生命周期问题)

2.makes your code simpler(让你的代码变得更简洁)

3.is fast(很快)

4.is tiny (~50k jar)(很小(jar包只有50k))

5.is proven in practice by apps with 100,000,000+ installs(在实践中超过100,000,000的app安装得到了证明)

6.has advanced features like delivery threads, subscriber priorities, etc.(拥有先进的功能,如交付线程,用户优先级等。)

 

EventBus in 3 steps(EventBus使用的3个步骤)：

1.Define events:(定义事件)

public static class MessageEvent {

/* Additional fields if needed */ (如果需要额外的字段)

 }

2.Prepare subscribers: Declare and annotate your subscribing method, optionally specify a thread mode:(准备订阅者：声明和注释你的订阅方法,选择指定线程模式)

@Subscribe(threadMode = ThreadMode.MAIN)  

public void onMessageEvent(MessageEvent event) {/* Do something */};

 

Register and unregister your subscriber. For example on Android, activities and fragments should usually register according to their life cycle:(注册和注销你的用户。例如在Android上,活动和碎片应该根据其生命周期注册)

 @Override

 public void onStart() {

     super.onStart();

     EventBus.getDefault().register(this);

 }

 

 @Override

 public void onStop() {

     super.onStop();

     EventBus.getDefault().unregister(this);

 }

(官网上面写了两个Activity生命周期中注册和注销，但我的建议是在Oncreate方法中注册，OnDestroy方法中注销)

 

3.Post events(发布事件)

EventBus.getDefault().post(new MessageEvent());

依赖：

Gradle:

compile 'org.greenrobot:eventbus:3.0.0'

简单的使用案例：

package xuechuan.com.myeventbustest;

import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

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

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private TextView mTv;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //注册EventBus
        EventBus.getDefault().register(this);
        mTv = (TextView) findViewById(R.id.tv);
        Button button = (Button) findViewById(R.id.btn_main);
        button.setOnClickListener(this);


    }


    @Override
    public void onClick(View view) {
        int id = view.getId();
        switch (id)   {
            case R.id.btn_main:
                Intent intent = new Intent(MainActivity.this,SecondActivity.class);
                startActivity(intent);
        }
    }

    @Subscribe(threadMode = ThreadMode.MAIN)
    public void onEventMessage(EventMessage event) {
        String msg = event.getMsg();
        mTv.setText(msg);
        Toast.makeText(this,msg,Toast.LENGTH_SHORT).show();
    }


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

        //反注册EventBus
        EventBus.getDefault().unregister(this);
    }
}

package xuechuan.com.myeventbustest;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;

import org.greenrobot.eventbus.EventBus;

public class SecondActivity extends AppCompatActivity {

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

        Button btnSendEvent = (Button) findViewById(R.id.btn_second);
        btnSendEvent.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                //发送消息
                EventBus.getDefault().post(new EventMessage("我这边好了，你可以修改UI了"));
            }
        });
    }
}

package xuechuan.com.myeventbustest;

/**
 * Created by Administrator on 2017/3/26.
 */

public class EventMessage {

    private String mMsg;
    public EventMessage(String msg) {
            this.mMsg=msg;
    }

    public String getMsg() {
        return mMsg;
    }
}