EventBus的使用详解
源码地址:https://github.com/greenrobot/EventBus
EventBus是一个Android 端优化的Publish/Subscribe 消息总线,它简化了应用程序内各组件间、组件与后台线程间的通信。比如请求网络等网络返回时通过Handler 或Broadcast 通知UI,两个Fragment 之间需要通过Listener 通信,这些需求都可以通过 EventBus 实现,最常见的就是它可以代替Intent,HandlerBroadCase 在Activity,Service,Fragment 间传递消息。
Eventbus作为事件总线,它主要有三个元素:
基本使用: (1)自定义一个类,可以是空类,比如:
public class AnyEventType {
public AnyEventType(){}
}
(2)在要接收消息的页面注册:
eventBus.register(this);
(3)发送消息
eventBus.post(new AnyEventType event);
public void onEvent(AnyEventType event) {}
public void onEventMainThread(AnyEventType event) {}
public void onEventBackgroundThread(AnyEventType event) {}
public void onEventAsync(AnyEventType event) {}
eventBus.unregister(this);
实战:
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)
MainActivity.java (点击btn跳转到第二个Activity)
package com.nova.eventbus_1;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
import org.greenrobot.eventbus.EventBus;
import org.greenrobot.eventbus.Subscribe;
public class MainActivity extends AppCompatActivity {
private Button button_jump;
private TextView tv_notify;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
button_jump= (Button) findViewById(R.id.bt_jump);
tv_notify= (TextView) findViewById(R.id.tv_notify);
button_jump.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent=new Intent(MainActivity.this,SecondActivity.class);
startActivityForResult(intent,1);
}
});
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
switch (requestCode){
case 1:
if(resultCode==1){
String returnedData=data.getStringExtra("com.nova.eventbus_1.data_return");
tv_notify.setText(returnedData);
Toast.makeText(MainActivity.this,returnedData,Toast.LENGTH_LONG).show();
Log.i("现在的线程",Thread.currentThread().getName());
}
}
}
}
SecondActivity.java
import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import org.greenrobot.eventbus.EventBus;
/**
* Created by Nova on 2016/4/11.
*/
public class SecondActivity extends AppCompatActivity {
private Button button_post;
private Button button_post2;//使用EventBus传递
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_two);
button_post= (Button) findViewById(R.id.bt_post);
button_post2= (Button) findViewById(R.id.bt_post2);
button_post.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent=new Intent();
intent.putExtra("com.nova.eventbus_1.data_return","跳转按钮:被点击了");
setResult(1,intent);
finish();
}
});
}
}
2、新建一个类FirstEvent
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。
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:
package com.nova.eventbus_1;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
import org.greenrobot.eventbus.EventBus;
import org.greenrobot.eventbus.Subscribe;
public class MainActivity extends AppCompatActivity {
private Button button_jump;
private TextView tv_notify;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//注册EventBus
EventBus.getDefault().register(MainActivity.this);
button_jump= (Button) findViewById(R.id.bt_jump);
tv_notify= (TextView) findViewById(R.id.tv_notify);
button_jump.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent=new Intent(MainActivity.this,SecondActivity.class);
startActivityForResult(intent,1);
}
});
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
switch (requestCode){
case 1:
if(resultCode==1){
String returnedData=data.getStringExtra("com.nova.eventbus_1.data_return");
tv_notify.setText(returnedData);
Toast.makeText(MainActivity.this,returnedData,Toast.LENGTH_LONG).show();
Log.i("现在的线程",Thread.currentThread().getName());
}
}
}
@Subscribe
public void onEventMainThread(FirstEvent event){
String msg="onEventMainThread收到了消息:" + event.getMsg();
tv_notify.setText(msg);
Toast.makeText(MainActivity.this,msg,Toast.LENGTH_LONG).show();
Log.i("现在的线程",Thread.currentThread().getName());
}
@Override
protected void onDestroy() {
super.onDestroy();
EventBus.getDefault().unregister(MainActivity.this);
}
}
EventBus.getDefault().post(new FirstEvent("跳转按钮:被点击了EventBus post"));
package com.nova.eventbus_1; import android.content.Intent; import android.os.Bundle; import android.support.annotation.Nullable; import android.support.v7.app.AppCompatActivity; import android.view.View; import android.widget.Button; import org.greenrobot.eventbus.EventBus; /** * Created by Nova on 2016/4/11. */ public class SecondActivity extends AppCompatActivity { private Button button_post; private Button button_post2;//使用EventBus传递 @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_two); button_post= (Button) findViewById(R.id.bt_post); button_post2= (Button) findViewById(R.id.bt_post2); button_post.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Intent intent=new Intent(); intent.putExtra("com.nova.eventbus_1.data_return","跳转按钮:被点击了"); setResult(1,intent); finish(); } }); button_post2.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { //EventBus使用方法 EventBus.getDefault().post(new FirstEvent("跳转按钮:被点击了EventBus post")); finish(); } }); } }
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;
@Subscribe public void onEventMainThread(FirstEvent event){ String msg="onEventMainThread收到了消息:" + event.getMsg(); tv_notify.setText(msg); Toast.makeText(MainActivity.this,msg,Toast.LENGTH_LONG).show(); Log.i("现在的线程",Thread.currentThread().getName()); }
@Subscribe
public void onEventMainThread(FirstEvent event){
String msg="onEventMainThread收到了消息:" + event.getMsg();
tv_notify.setText(msg);
Toast.makeText(MainActivity.this,msg,Toast.LENGTH_LONG).show();
Log.i("现在的线程",Thread.currentThread().getName());
}