第一步：在build.gradle中新增依賴

 dependencies {
    compile 'org.greenrobot:eventbus:3.0.0'
}
第二步：建立一個 Event類： 注意：enum 不是class

 public enum  Event {
//訊息名，可以根據這個名字判斷是哪個訊息
IMAGE_LOADER_SUCCESS;
}

//------------主佈局檔案------------------------
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
 
android:id="@+id/tv_text" />
<Button
android:layout_width="match_parent"
android:layout_height="40dp"
android:text="點選跳轉到TwoActivity"
android:id="@+id/bt_button"/>


//-----------TwoActivity佈局-----------------------
<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
 
android:id="@+id/bt_button2"
android:text="傳送訊息"/>



//---------建立一個訊息了---MessageEvent ------------------------
public class MessageEvent {
        private String message;

        public String getMessage() {
            return message;
        }

        public void setMessage(String message) {
            this
 
.message = message;
        }

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

        public MessageEvent() {
        }
    }


//--------------MainActivity -中我們註冊事件，用於接收訊息，退出時需要登出-----------------
package eventbusdemo.wode.com.eventbusdemo;

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

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

    public class MainActivity extends AppCompatActivity implements View.OnClickListener{

        private Button bt_button;
        private TextView tv_text;

        @Override
protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            //找到控制元件
bt_button = (Button) findViewById(R.id.bt_button);
            tv_text = (TextView) findViewById(R.id.tv_text);
            //在需要訂閱事件的地方註冊事件
EventBus.getDefault().register(this);
            //設定監聽
bt_button.setOnClickListener(this);

        }
        //用於接收傳MessageEvent這個類的訊息
@Subscribe(threadMode = ThreadMode.MAIN)
        public void onShowMessageEvent(MessageEvent messageEvent) {
            tv_text.setText("MainActivity:" + messageEvent.getMessage());
        }

        //用於接收沒有傳值的訊息
/* @Subscribe
    public void onEventMainThread(Event event){
        switch (event){
            case IMAGE_LOADER_SUCCESS:
                Log.i("MainActivity--","IMAGE_LOADER_SUCCESS");
                tv_text.setText("IMAGE_LOADER_SUCCESS");
                break;
        }
    }*/
@Override
public void onClick(View v) {
            switch (v.getId()){
                case R.id.bt_button:
                    Intent intent=new Intent(MainActivity.this,TwoActivity.class);
                    startActivity(intent);
                    break;
            }
        }

        //(5)取消訊息訂閱
@Override
protected void onDestroy() {
            super.onDestroy();
            EventBus.getDefault().unregister(this);
        }
    }



//--------------TwoActivity 中，用於傳送訊息------------------------
package eventbusdemo.wode.com.eventbusdemo;

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

import org.greenrobot.eventbus.EventBus;

    public class TwoActivity extends AppCompatActivity {

        @Override
protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_two);
            Button bt_button2= (Button) findViewById(R.id.bt_button2);
            bt_button2.setOnClickListener(new View.OnClickListener() {
                @Override
public void onClick(View v) {
                    //(3)產生事件，即傳送訊息
// EventBus.getDefault().post(Event.IMAGE_LOADER_SUCCESS);
                    //傳值
EventBus.getDefault().post(new MessageEvent("哈哈哈哈哈"));
                }
            });

        }
    }