Question

19.2. 快速开始一个演示例子

操作 EventBus 只需四个步骤

		
1. 注册事件

EventBus.getDefault().register( this );

2. 取消注册

EventBus.getDefault().unregister( this );

3. 订阅事件

	@Subscribe(threadMode = ThreadMode.MAIN)
    public void onMessageEvent(MessageEvent event) {
        Toast.makeText(this, event.message, Toast.LENGTH_SHORT).show();
    }

4. 发送数据

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

19.2.1. 创建 MessageEvent 类

			
package cn.netkiller.eventbus.pojo;

public class MessageEvent {
    public final String message;

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

19.2.2. Layout

			
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:text="Button"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView" />

</android.support.constraint.ConstraintLayout>			
			
			

19.2.3. Activity

			
package cn.netkiller.eventbus;

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

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

import cn.netkiller.eventbus.pojo.MessageEvent;

public class MainActivity extends AppCompatActivity {

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

        EventBus.getDefault().register(this);

        findViewById(R.id.button).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                EventBus.getDefault().post(new MessageEvent("Hello everyone!"));
            }
        });

    }

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

        //取消注册 , 防止Activity内存泄漏
        EventBus.getDefault().unregister(this);
    }

    @Subscribe(threadMode = ThreadMode.MAIN)
    public void onMessageEvent(MessageEvent event) {
        Toast.makeText(this, event.message, Toast.LENGTH_SHORT).show();
    }
}