EventBus

apply plugin: 'com.android.application'

android {
    compileSdkVersion 26
    buildToolsVersion "27.0.1"

    defaultConfig {
        applicationId "com.bwie.eventbuslian"
        minSdkVersion 16
        targetSdkVersion 26
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        javaCompileOptions {
            annotationProcessorOptions
                    {
                        arguments = [eventBusIndex: 'com.bwie.butterknife.MyEventBusIndex']
                    }
        }
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.android.support:appcompat-v7:26.+'
    compile 'com.android.support.constraint:constraint-layout:1.0.2'
    compile 'org.greenrobot:eventbus:3.1.1'
    testCompile 'junit:junit:4.12'
    annotationProcessor 'org.greenrobot:eventbus-annotation-processor:3.1.1'
}

package com.bwie.eventbuslian;

/**
 * Created by lenovo on 2017/11/29.
 */

public class First {
    private String Msg;

    public First(String msg) {
        Msg = msg;
    }

    public String getMsg() {
        return Msg;
    }
}

package com.bwie.eventbuslian;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
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 Main2Activity extends AppCompatActivity {

    private TextView tv2;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);
        EventBus.getDefault().register(this);
         tv2= (TextView) findViewById(R.id.tv_2);
        findViewById(R.id.bt_2).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                startActivity(new Intent(getApplicationContext(),SecondActivity.class));
            }
        });

    }
    @Subscribe(threadMode = ThreadMode.MAIN)
    public void onEventBusMainThread(First first){
         String f="消息是"+first.getMsg();
        tv2.setText(f);
        Toast.makeText(this,f, Toast.LENGTH_SHORT).show();
    }
    @Override
    protected void onDestroy() {
        super.onDestroy();
        EventBus.getDefault().unregister(this);
    }
}

package com.bwie.eventbuslian;

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.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 {
    private TextView tv;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //注册EventBus
        EventBus.getDefault().register(this);
         tv = (TextView) findViewById(R.id.tv);
        findViewById(R.id.bt).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                startActivity(new Intent(getApplicationContext(),SecondActivity.class));
            }
        });
        findViewById(R.id.bt_main2).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                startActivity(new Intent(MainActivity.this,Main2Activity.class));
            }
        });
    }
    @Subscribe(threadMode = ThreadMode.MAIN)
public void  onEventMainThread(First first){
    String msg="接受到的消息是"+first.getMsg();
    Log.e("哈哈哈哈",msg);
    tv.setText(msg);
    Toast.makeText(this,"hahahahahahaahahaha"+msg, Toast.LENGTH_SHORT).show();
}
    @Override
    protected void onDestroy() {
        super.onDestroy();
        EventBus.getDefault().unregister(this);//取消注册
    }
}

package com.bwie.eventbuslian;

import android.content.Intent;
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 SecondActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);
        Button bt= (Button) findViewById(R.id.bt_fa);
        bt.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                EventBus.getDefault().post(new First("郭宇雷...shit"));
            finish();
            }
        });
    }
}