compile 'org.greenrobot:eventbus:3.0.0'

public class MainActivity extends AppCompatActivity {
  private Button button_t,button_d;
  private TextView tv_a;
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    button_d=(Button)findViewById(R.id.button_d);
    button_d.setText("订阅");
    button_t=(Button)findViewById(R.id.button_t);
    button_t.setText("跳转到Bctivity");
    tv_a=(TextView)findViewById(R.id.tv_a);
    tv_a.setText("欢迎大家观看飞鸟96的博客");
    button_t.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View view) {
        startActivity(new Intent(MainActivity.this,MainBctivity.class));
      }
    });
    /*
    * 订阅事件
    * */
    button_d.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View view) {
        if(!EventBus.getDefault().isRegistered(MainActivity.this)) {
          EventBus.getDefault().register(MainActivity.this);
        }else{
          Toast.makeText(MainActivity.this, "请勿重复注册事件", Toast.LENGTH_SHORT).show();
        }
      }
    });
  }

  @Override
  protected void onDestroy() {
    super.onDestroy();
    /*
    * 取消注册事件
    * */
    EventBus.getDefault().unregister(MainActivity.this);
  }
  @Subscribe(threadMode = ThreadMode.MAIN)
  public void onMoonEvent(MessageEvent message){
    tv_a.setText(message.getMessage());
  }
  @Subscribe(sticky = true)
  public void onMoonEvents(MessageEvent message){
    tv_a.setText(message.getMessage());
  }
}

public class MainBctivity extends AppCompatActivity {
  private Button button_f,button_n;
  private TextView tv_b;
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main_bctivity);
    button_f=(Button)findViewById(R.id.button_f);
    button_f.setText("发送事件");
    button_n=(Button)findViewById(R.id.button_n);
    button_n.setText("粘性事件");
    tv_b=(TextView)findViewById(R.id.tv_b);
    tv_b.setText("MainBctivity");
    /*发送事件*/
    button_f.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View view) {
        EventBus.getDefault().post(new MessageEvent("飞鸟96博客祝你用的开心！"));
        finish();
      }
    });
    /*粘性事件*/
    button_n.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View view) {
        EventBus.getDefault().postSticky(new MessageEvent("开心开心开开心！！"));
        finish();
      }
    });

  }
}

public class MessageEvent {
  private String message;

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

  public MessageEvent() {
  }

  public String getMessage() {
    return message;
  }

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

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Hello World!"
    android:layout_centerInParent="true"
    android:id="@+id/tv_a" />

  <Button
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="17dp"
    android:id="@+id/button_t"
    android:layout_below="@id/tv_a" />
  <Button
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="17dp"
    android:id="@+id/button_d"
    android:layout_below="@id/button_t" />

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Hello World!"
    android:layout_centerInParent="true"
    android:id="@+id/tv_b" />

  <Button
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="17dp"
    android:id="@+id/button_f"
    android:layout_below="@id/tv_b" />
  <Button
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="17dp"
    android:id="@+id/button_n"
    android:layout_below="@id/button_f" />