EventBus(一)

案例效果：

当击btn_try按钮的时候，跳到第二个Activity，当点击第二个activity上面的First Event按钮的时候向第一个Activity发送消息，当第一个Activity收到消息后，一方面将消息Toast显示，一方面放入textView中显示。

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
    
    <Button 
        android:id="@+id/btn_try"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="btn_bty"/>
    <TextView 
        android:id="@+id/tv"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"/>

</LinearLayout>

activity_second.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.harvic.try_eventbus_1.SecondActivity" >

    <Button 
        android:id="@+id/btn_first_event"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="First Event"/>

</LinearLayout>

FirstEvent

package com.harvic.other;
/**
 * 用来构造消息的
 * 对外提供一个方法getMsg，获取消息内容即可
 *
 */
<span style="color:#FF0000;">public class FirstEvent {

	private String mMsg;
	public FirstEvent(String msg) {
		mMsg = msg;
	}
	public String getMsg(){
		return mMsg;
	}
}</span>

MainActivity

package com.example.tryeventbus_simple;

import com.harvic.other.FirstEvent;

import de.greenrobot.event.EventBus;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {

	Button btn;
	TextView tv;

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

		//注册EventBus
		EventBus.getDefault().register(this);</span>

		btn = (Button) findViewById(R.id.btn_try);
		tv = (TextView)findViewById(R.id.tv);

		btn.setOnClickListener(new View.OnClickListener() {

			@Override
			public void onClick(View v) {
				Intent intent = new Intent(getApplicationContext(),
						SecondActivity.class);
				startActivity(intent);
			}
		});
	}
        /**
	 * 我们使用EventBus中最常用的onEventMainThread（）函数来接收消息
	 */
	public void onEventMainThread(FirstEvent event) {

		String msg = "onEventMainThread收到了消息：" + event.getMsg();
		Log.d("harvic", msg);
		tv.setText(msg);
		Toast.makeText(this, msg, Toast.LENGTH_LONG).show();
	}

	@Override
	protected void onDestroy(){
		super.onDestroy();
		EventBus.getDefault().unregister(this);
	}
}

SecondActivity

package com.example.tryeventbus_simple;

import com.harvic.other.FirstEvent;

import de.greenrobot.event.EventBus;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class SecondActivity extends Activity {
	private Button btn_FirstEvent;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_second);
		btn_FirstEvent = (Button) findViewById(R.id.btn_first_event);

		btn_FirstEvent.setOnClickListener(new View.OnClickListener() {

			@Override
			public void onClick(View v) {
				//发送消息是使用EventBus中的Post方法来实现发送的，发送过去的是我们新建的类的实例
				EventBus.getDefault().post(
						new FirstEvent("FirstEvent btn clicked"));
			}
		});


	}

}