一、概述
前一篇給大家裝簡單演示了EventBus的onEventMainThread()函數的接收,其實EventBus還有另外有個不同的函數,他們分別是:
1、onEvent
2、onEventMainThread
3、onEventBackgroundThread
4、onEventAsync
這四種訂閱函數都是使用onEvent開頭的,它們的功能稍有不同,在介紹不同之前先介紹兩個概念:
告知觀察者事件發生時通過EventBus.post函數實現,這個過程叫做事件的發佈,觀察者被告知事件發生叫做事件的接收,是通過下面的訂閱函數實現的。
onEvent:如果使用onEvent作爲訂閱函數,那麼該事件在哪個線程發佈出來的,onEvent就會在這個線程中運行,也就是說發佈事件和接收事件線程在同一個線程。使用這個方法時,在onEvent方法中不能執行耗時操作,如果執行耗時操作容易導致事件分發延遲。
onEventMainThread:如果使用onEventMainThread作爲訂閱函數,那麼不論事件是在哪個線程中發佈出來的,onEventMainThread都會在UI線程中執行,接收事件就會在UI線程中運行,這個在Android中是非常有用的,因爲在Android中只能在UI線程中跟新UI,所以在onEvnetMainThread方法中是不能執行耗時操作的。
onEventBackground:如果使用onEventBackgrond作爲訂閱函數,那麼如果事件是在UI線程中發佈出來的,那麼onEventBackground就會在子線程中運行,如果事件本來就是子線程中發佈出來的,那麼onEventBackground函數直接在該子線程中執行。
onEventAsync:使用這個函數作爲訂閱函數,那麼無論事件在哪個線程發佈,都會創建新的子線程在執行onEventAsync.
二、實戰
1、解析
上面列出的這四個函數,關鍵問題在於,我們怎麼指定調用哪個函數呢?
我們先研究一下,上一篇中是怎麼調用的onEventMainThread函數,除了在接收端註冊與反註冊以後,關鍵問題在於新建的一個類:
新建一個類:
- 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;
- }
- }
- EventBus.getDefault().post(new FirstEvent("FirstEvent btn clicked"));
- public void onEventMainThread(FirstEvent event) {
- ……
- }
沒錯,發送時發送的是這個類的實例,接收時參數就是這個類實例。
所以!!!!!!當發過來一個消息的時候,EventBus怎麼知道要調哪個函數呢,就看哪個函數傳進去的參數是這個類的實例,哪個是就調哪個。那如果有兩個是呢,那兩個都會被調用!!!!
爲了證明這個問題,下面寫個例子,先看下效果
2、實例
先看看我們要實現的效果:
這次我們在上一篇的基礎上,新建三個類:FirstEvent、SecondEvent、ThirdEvent,在第二個Activity中發送請求,在MainActivity中接收這三個類的實例,接收時的代碼爲:
- public void onEventMainThread(FirstEvent event) {
- Log.d("harvic", "onEventMainThread收到了消息:" + event.getMsg());
- }
- public void onEventMainThread(SecondEvent event) {
- Log.d("harvic", "onEventMainThread收到了消息:" + event.getMsg());
- }
- public void onEvent(ThirdEvent event) {
- Log.d("harvic", "OnEvent收到了消息:" + event.getMsg());
- }
Log輸出結果:
可以看到,在發送FirstEvent時,在MainActiviy中雖然有三個函數,但只有第一個onEventMainThread函數的接收參數是FirstEvent,所以會傳到它這來接收。所以這裏識別調用EventBus中四個函數中哪個函數,是通過參數中的實例來決定的。
因爲我們是在上一篇例子的基礎上完成的,所以這裏的代碼就不詳細寫了,只寫改動的部分。
1、三個類
- 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;
- }
- }
- package com.harvic.other;
- public class SecondEvent{
- private String mMsg;
- public SecondEvent(String msg) {
- // TODO Auto-generated constructor stub
- mMsg = "MainEvent:"+msg;
- }
- public String getMsg(){
- return mMsg;
- }
- }
- package com.harvic.other;
- public class ThirdEvent {
- private String mMsg;
- public ThirdEvent(String msg) {
- // TODO Auto-generated constructor stub
- mMsg = msg;
- }
- public String getMsg(){
- return mMsg;
- }
- }
2、發送
然後在SecondActivity中新建三個按鈕,分別發送不同的類的實例,代碼如下:
- package com.harvic.tryeventbus2;
- import com.harvic.other.FirstEvent;
- import com.harvic.other.SecondEvent;
- import com.harvic.other.ThirdEvent;
- 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, btn_SecondEvent, btn_ThirdEvent;
- @Override
- protected void onCreate(Bundle savedInstanceState) {
- super.onCreate(savedInstanceState);
- setContentView(R.layout.activity_second);
- btn_FirstEvent = (Button) findViewById(R.id.btn_first_event);
- btn_SecondEvent = (Button) findViewById(R.id.btn_second_event);
- btn_ThirdEvent = (Button) findViewById(R.id.btn_third_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"));
- }
- });
- btn_SecondEvent.setOnClickListener(new View.OnClickListener() {
- @Override
- public void onClick(View v) {
- // TODO Auto-generated method stub
- EventBus.getDefault().post(
- new SecondEvent("SecondEvent btn clicked"));
- }
- });
- btn_ThirdEvent.setOnClickListener(new View.OnClickListener() {
- @Override
- public void onClick(View v) {
- // TODO Auto-generated method stub
- EventBus.getDefault().post(
- new ThirdEvent("ThirdEvent btn clicked"));
- }
- });
- }
- }
3、接收
在MainActivity中,除了註冊與註冊,我們利用onEventMainThread(FirstEvent event)來接收來自FirstEvent的消息,使用onEventMainThread(SecondEvent event)接收來自SecondEvent 實例的消息,使用onEvent(ThirdEvent event) 來接收ThirdEvent 實例的消息。- package com.harvic.tryeventbus2;
- import com.harvic.other.FirstEvent;
- import com.harvic.other.SecondEvent;
- import com.harvic.other.ThirdEvent;
- import de.greenrobot.event.EventBus;
- import android.app.Activity;
- import android.content.Intent;
- import android.os.Bundle;
- import android.util.Log;
- import android.view.Menu;
- import android.view.MenuItem;
- import android.view.View;
- import android.widget.Button;
- import android.widget.TextView;
- public class MainActivity extends Activity {
- Button btn;
- TextView tv;
- EventBus eventBus;
- @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);
- 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) {
- Log.d("harvic", "onEventMainThread收到了消息:" + event.getMsg());
- }
- public void onEventMainThread(SecondEvent event) {
- Log.d("harvic", "onEventMainThread收到了消息:" + event.getMsg());
- }
- public void onEvent(ThirdEvent event) {
- Log.d("harvic", "OnEvent收到了消息:" + event.getMsg());
- }
- @Override
- protected void onDestroy() {
- // TODO Auto-generated method stub
- super.onDestroy();
- EventBus.getDefault().unregister(this);
- }
- }
在MainActivity中接收時,我們在接收SecondEvent時,在上面onEventMainThread基礎上另加一個onEventBackgroundThread和onEventAsync,即下面的代碼:
- //SecondEvent接收函數一
- public void onEventMainThread(SecondEvent event) {
- Log.d("harvic", "onEventMainThread收到了消息:" + event.getMsg());
- }
- //SecondEvent接收函數二
- public void onEventBackgroundThread(SecondEvent event){
- Log.d("harvic", "onEventBackground收到了消息:" + event.getMsg());
- }
- //SecondEvent接收函數三
- public void onEventAsync(SecondEvent event){
- Log.d("harvic", "onEventAsync收到了消息:" + event.getMsg());
- }
- package com.harvic.tryeventbus2;
- import com.harvic.other.FirstEvent;
- import com.harvic.other.SecondEvent;
- import com.harvic.other.ThirdEvent;
- import de.greenrobot.event.EventBus;
- import android.app.Activity;
- import android.content.Intent;
- import android.os.Bundle;
- import android.util.Log;
- import android.view.Menu;
- import android.view.MenuItem;
- import android.view.View;
- import android.widget.Button;
- import android.widget.TextView;
- public class MainActivity extends Activity {
- Button btn;
- TextView tv;
- EventBus eventBus;
- @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);
- 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) {
- Log.d("harvic", "onEventMainThread收到了消息:" + event.getMsg());
- }
- //SecondEvent接收函數一
- public void onEventMainThread(SecondEvent event) {
- Log.d("harvic", "onEventMainThread收到了消息:" + event.getMsg());
- }
- //SecondEvent接收函數二
- public void onEventBackgroundThread(SecondEvent event){
- Log.d("harvic", "onEventBackground收到了消息:" + event.getMsg());
- }
- //SecondEvent接收函數三
- public void onEventAsync(SecondEvent event){
- Log.d("harvic", "onEventAsync收到了消息:" + event.getMsg());
- }
- public void onEvent(ThirdEvent event) {
- Log.d("harvic", "OnEvent收到了消息:" + event.getMsg());
- }
- @Override
- protected void onDestroy() {
- // TODO Auto-generated method stub
- super.onDestroy();
- EventBus.getDefault().unregister(this);
- }
- }
好啦,這篇就到了,講來講去就是說一個問題:消息的接收是根據參數中的類名來決定執行哪一個的;
參考文章:
《Android解耦庫EventBus的使用和源碼分析》:http://blog.csdn.net/yuanzeyao/article/details/38174537
《EventBus的使用初試》:http://blog.csdn.net/pp_hdsny/article/details/14523561
《EventBusExplained 》:https://code.google.com/p/guava-libraries/wiki/EventBusExplained
如果我的文章有幫到你,記得關注哦!
源碼下載地址:http://download.csdn.net/detail/harvic880925/8128633
請大家尊重原創者版權,轉載請標明出處:http://blog.csdn.net/harvic880925/article/details/40787203 謝謝!