EventBus的使用

逃离我推掉我的手 2022-06-09 07:50 233阅读 0赞

**相关文章：**

**1、[《EventBus使用详解(一)——初步使用EventBus》][EventBus_EventBus]**

**2、[《EventBus使用详解(二)——EventBus使用进阶》][EventBus_EventBus 1]**

## 一、概述 ##

EventBus是一款针对[Android][]优化的发布/订阅事件总线。主要功能是替代Intent,Handler,BroadCast在Fragment，Activity，Service，线程之间传递消息.优点是开销小，代码更优雅。以及将发送者和接收者解耦。  
1、下载EventBus的类库  
源码：[https://github.com/greenrobot/EventBus][https_github.com_greenrobot_EventBus]

2、基本使用

（1）自定义一个类，可以是空类，比如：

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1.  public class AnyEventType \{
2.  public AnyEventType()\{\}
3.  \}

public class AnyEventType {
    	 public AnyEventType(){}
     }

（2）在要接收消息的页面注册：

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1.  eventBus.register(this);

eventBus.register(this);

（3）发送消息

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1.  eventBus.post(new AnyEventType event);

eventBus.post(new AnyEventType event);

（4）接受消息的页面实现(共有四个函数，各功能不同，这是其中之一，可以选择性的实现，这里先实现一个)：

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1.  public void onEvent(AnyEventType event) \{\}

public void onEvent(AnyEventType event) {}

（5）解除注册

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1.  eventBus.unregister(this);

eventBus.unregister(this);

顺序就是这么个顺序，可真正让自己写，估计还是云里雾里的，下面举个例子来说明下。

首先，在EventBus中，获取实例的方法一般是采用EventBus.getInstance()来获取默认的EventBus实例，当然你也可以new一个又一个，个人感觉还是用默认的比较好，以防出错。

## 二、实战 ##

先给大家看个例子：

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。

![20141102142444304][]

按照下面的步骤，下面来建这个工程：

### 1、基本框架搭建 ###

想必大家从一个Activity跳转到第二个Activity的程序应该都会写，这里先稍稍把两个Activity跳转的代码建起来。后面再添加EventBus相关的玩意。

**MainActivity布局（activity\_main.xml）**

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1.  <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
2.  xmlns:tools="http://schemas.android.com/tools"
3.  android:layout\_width="match\_parent"
4.  android:layout\_height="match\_parent"
5.  android:orientation="vertical">
6.  
7.  <Button
8.  android:id="@+id/btn\_try"
9.  android:layout\_width="match\_parent"
10. android:layout\_height="wrap\_content"
11. android:text="btn\_bty"/>
12. <TextView
13. android:id="@+id/tv"
14. android:layout\_width="wrap\_content"
15. android:layout\_height="match\_parent"/>
16. 
17. </LinearLayout>

**新建一个Activity，SecondActivity布局（activity\_second.xml）**

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1.  <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
2.  xmlns:tools="http://schemas.android.com/tools"
3.  android:layout\_width="match\_parent"
4.  android:layout\_height="match\_parent"
5.  android:orientation="vertical"
6.  tools:context="com.harvic.try\_eventbus\_1.SecondActivity" >
7.  
8.  <Button
9.  android:id="@+id/btn\_first\_event"
10. android:layout\_width="match\_parent"
11. android:layout\_height="wrap\_content"
12. android:text="First Event"/>
13. 
14. </LinearLayout>

**MainActivity.java （点击btn跳转到第二个Activity）**

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1.  public class MainActivity extends Activity \{
2.  
3.  Button btn;
4.  
5.  @Override
6.  protected void onCreate(Bundle savedInstanceState) \{
7.  super.onCreate(savedInstanceState);
8.  setContentView(R.layout.activity\_main);
9.  
10. btn = (Button) findViewById(R.id.btn\_try);
11. 
12. btn.setOnClickListener(new View.OnClickListener() \{
13. 
14. @Override
15. public void onClick(View v) \{
16. // TODO Auto-generated method stub
17. Intent intent = new Intent(getApplicationContext(),
18. SecondActivity.class);
19. startActivity(intent);
20. \}
21. \});
22. \}
23. 
24. \}

public class MainActivity extends Activity {
    
    	Button btn;
    
    	@Override
    	protected void onCreate(Bundle savedInstanceState) {
    		super.onCreate(savedInstanceState);
    		setContentView(R.layout.activity_main);
    
    		btn = (Button) findViewById(R.id.btn_try);
    
    		btn.setOnClickListener(new View.OnClickListener() {
    
    			@Override
    			public void onClick(View v) {
    				// TODO Auto-generated method stub
    				Intent intent = new Intent(getApplicationContext(),
    						SecondActivity.class);
    				startActivity(intent);
    			}
    		});
    	}
    
    }

到这，基本框架就搭完了，下面开始按步骤使用EventBus了。

### 2、新建一个类FirstEvent ###

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1.  package com.harvic.other;
2.  
3.  public class FirstEvent \{
4.  
5.  private String mMsg;
6.  public FirstEvent(String msg) \{
7.  // TODO Auto-generated constructor stub
8.  mMsg = msg;
9.  \}
10. public String getMsg()\{
11. return mMsg;
12. \}
13. \}

package com.harvic.other;
    
    public class FirstEvent {
    
    	private String mMsg;
    	public FirstEvent(String msg) {
    		// TODO Auto-generated constructor stub
    		mMsg = msg;
    	}
    	public String getMsg(){
    		return mMsg;
    	}
    }

这个类很简单，构造时传进去一个字符串，然后可以通过getMsg()获取出来。

### 3、在要接收消息的页面注册EventBus： ###

在上面的GIF图片的演示中，大家也可以看到，我们是要在MainActivity中接收发过来的消息的，所以我们在MainActivity中注册消息。

通过我们会在OnCreate()函数中注册EventBus，在OnDestroy（）函数中反注册。所以整体的注册与反注册的代码如下：

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1.  package com.example.tryeventbus\_simple;
2.  
3.  import com.harvic.other.FirstEvent;
4.  
5.  import de.greenrobot.event.EventBus;
6.  import android.app.Activity;
7.  import android.content.Intent;
8.  import android.os.Bundle;
9.  import android.util.Log;
10. import android.view.View;
11. import android.widget.Button;
12. import android.widget.TextView;
13. import android.widget.Toast;
14. 
15. public class MainActivity extends Activity \{
16. 
17. Button btn;
18. TextView tv;
19. 
20. @Override
21. protected void onCreate(Bundle savedInstanceState) \{
22. super.onCreate(savedInstanceState);
23. setContentView(R.layout.activity\_main);
24. //注册EventBus
25. EventBus.getDefault().register(this);
26. 
27. btn = (Button) findViewById(R.id.btn\_try);
28. tv = (TextView)findViewById(R.id.tv);
29. 
30. btn.setOnClickListener(new View.OnClickListener() \{
31. 
32. @Override
33. public void onClick(View v) \{
34. // TODO Auto-generated method stub
35. Intent intent = new Intent(getApplicationContext(),
36. SecondActivity.class);
37. startActivity(intent);
38. \}
39. \});
40. \}
41. @Override
42. protected void onDestroy()\{
43. super.onDestroy();
44. EventBus.getDefault().unregister(this);//反注册EventBus
45. \}
46. \}

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);
    
    		btn = (Button) findViewById(R.id.btn_try);
    		tv = (TextView)findViewById(R.id.tv);
    
    		btn.setOnClickListener(new View.OnClickListener() {
    
    			@Override
    			public void onClick(View v) {
    				// TODO Auto-generated method stub
    				Intent intent = new Intent(getApplicationContext(),
    						SecondActivity.class);
    				startActivity(intent);
    			}
    		});
    	}
    	@Override
    	protected void onDestroy(){
    		super.onDestroy();
    		EventBus.getDefault().unregister(this);//反注册EventBus
    	}
    }

### 4、发送消息 ###

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！

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1.  EventBus.getDefault().post(new FirstEvent("FirstEvent btn clicked"));

EventBus.getDefault().post(new FirstEvent("FirstEvent btn clicked"));

完整的SecondActivity.[Java][]的代码如下：

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1.  package com.example.tryeventbus\_simple;
2.  
3.  import com.harvic.other.FirstEvent;
4.  
5.  import de.greenrobot.event.EventBus;
6.  import android.app.Activity;
7.  import android.os.Bundle;
8.  import android.view.View;
9.  import android.widget.Button;
10. 
11. public class SecondActivity extends Activity \{
12. private Button btn\_FirstEvent;
13. 
14. @Override
15. protected void onCreate(Bundle savedInstanceState) \{
16. super.onCreate(savedInstanceState);
17. setContentView(R.layout.activity\_second);
18. btn\_FirstEvent = (Button) findViewById(R.id.btn\_first\_event);
19. 
20. btn\_FirstEvent.setOnClickListener(new View.OnClickListener() \{
21. 
22. @Override
23. public void onClick(View v) \{
24. // TODO Auto-generated method stub
25. EventBus.getDefault().post(
26. new FirstEvent("FirstEvent btn clicked"));
27. \}
28. \});
29. \}
30. \}

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) {
    				// TODO Auto-generated method stub
    				EventBus.getDefault().post(
    						new FirstEvent("FirstEvent btn clicked"));
    			}
    		});
    	}
    }

### 5、接收消息 ###

接收消息时，我们使用EventBus中最常用的onEventMainThread（）函数来接收消息，具体为什么用这个，我们下篇再讲，这里先给大家一个初步认识，要先能把EventBus用起来先。

在MainActivity中重写onEventMainThread（FirstEvent event），参数就是我们自己定义的类：

在收到Event实例后，我们将其中携带的消息取出，一方面Toast出去，一方面传到TextView中；

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1.  public void onEventMainThread(FirstEvent event) \{
2.  
3.  String msg = "onEventMainThread收到了消息：" \+ event.getMsg();
4.  Log.d("harvic", msg);
5.  tv.setText(msg);
6.  Toast.makeText(this, msg, Toast.LENGTH\_LONG).show();
7.  \}

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();
    	}

完整的MainActiviy代码如下：

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1.  package com.example.tryeventbus\_simple;
2.  
3.  import com.harvic.other.FirstEvent;
4.  
5.  import de.greenrobot.event.EventBus;
6.  import android.app.Activity;
7.  import android.content.Intent;
8.  import android.os.Bundle;
9.  import android.util.Log;
10. import android.view.View;
11. import android.widget.Button;
12. import android.widget.TextView;
13. import android.widget.Toast;
14. 
15. public class MainActivity extends Activity \{
16. 
17. Button btn;
18. TextView tv;
19. 
20. @Override
21. protected void onCreate(Bundle savedInstanceState) \{
22. super.onCreate(savedInstanceState);
23. setContentView(R.layout.activity\_main);
24. 
25. EventBus.getDefault().register(this);
26. 
27. btn = (Button) findViewById(R.id.btn\_try);
28. tv = (TextView)findViewById(R.id.tv);
29. 
30. btn.setOnClickListener(new View.OnClickListener() \{
31. 
32. @Override
33. public void onClick(View v) \{
34. // TODO Auto-generated method stub
35. Intent intent = new Intent(getApplicationContext(),
36. SecondActivity.class);
37. startActivity(intent);
38. \}
39. \});
40. \}
41. 
42. public void onEventMainThread(FirstEvent event) \{
43. 
44. String msg = "onEventMainThread收到了消息：" \+ event.getMsg();
45. Log.d("harvic", msg);
46. tv.setText(msg);
47. Toast.makeText(this, msg, Toast.LENGTH\_LONG).show();
48. \}
49. 
50. @Override
51. protected void onDestroy()\{
52. super.onDestroy();
53. EventBus.getDefault().unregister(this);
54. \}
55. \}

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);
    
    		EventBus.getDefault().register(this);
    
    		btn = (Button) findViewById(R.id.btn_try);
    		tv = (TextView)findViewById(R.id.tv);
    
    		btn.setOnClickListener(new View.OnClickListener() {
    
    			@Override
    			public void onClick(View v) {
    				// TODO Auto-generated method stub
    				Intent intent = new Intent(getApplicationContext(),
    						SecondActivity.class);
    				startActivity(intent);
    			}
    		});
    	}
    
    	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);
    	}
    }

好了，到这，基本上算初步把EventBus用起来了，下篇再讲讲EventBus的几个函数，及各个函数间是如何识别当前如何调用哪个函数的。

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[EventBus_EventBus]: http://blog.csdn.net/harvic880925/article/details/40660137
[EventBus_EventBus 1]: http://blog.csdn.net/harvic880925/article/details/40787203
[Android]: http://lib.csdn.net/base/android
[https_github.com_greenrobot_EventBus]: https://github.com/greenrobot/EventBus
[view plain]: http://blog.csdn.net/harvic880925/article/details/40660137#
[20141102142444304]: /images/20220609/75004736936346be87313a5069b6a30e.png
[Java]: http://lib.csdn.net/base/java
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