java– 如何从非活动线程调用活动？

概述我有一个使用Thread发送我自己的事件的ObserverDesignpattern.有时被调用的类是Android活动,有时它们是常规类.Thread中的代码不是Activity.我收到了这个错误：Can’tcreatehandlerinsidethreadthathasnotcalledLooper.prepare()为了避免运行时错误,我不得不在T

我有一个使用Thread发送我自己的事件的Observer Design pattern.有时被调用的类是AndroID活动,有时它们是常规类. Thread中的代码不是Activity.

我收到了这个错误：

Can’t create handler insIDe thread that has not called
Looper.prepare()

为了避免运行时错误,我不得不在Thread中添加Looper.prepare().我知道这篇文章：Can’t create handler inside thread that has not called Looper.prepare()它包含了这类问题的最佳信息,但我仍然不知道如何将mjosh的答案整合到我的主题中.

问题

从线程到活动的调用永远不会发生.孤立地,这个代码可以工作,但是当活动正在等待呼叫时.

该类将事件发送到其他类.这个用Thread运行.

public class EventBus{    // Non essential code here.    ...    // Thread code.    private class MyThread implements Runnable    {        @OverrIDe        public voID run()        {            while(true)            {               synchronized(List)               {                   for(Observer o : List)                       // Execution transfers to Activity here.                      o.handleEvent(event);                                  }            }         }      }}

在活动中.

public class FirstActivity extends Activity implements Observer{    public voID handleEvent()    {      // Never gets here.    }}

那么我该如何解决这个问题呢？我的整个应用程序将有许多活动和许多常规课程.

解决我的问题

我需要一种方法来保持我的线程活跃并调用活动.这可能是向Thread添加一些代码的混合,以便它可以成功地将我的调用发送到ActivitIEs.

解决方法:

虽然我没有为AndroID编程,但我认为在这里做你想做的事情并不困难.根据您链接问题中给出的答案,问题是您将拥有可能是也可能不是活动的观察者.由于Activity线程模型的性质,您无法简单地处理活动上的事件.对于活动,您需要在UI线程上完成 *** 作.这听起来相当紧张.使用POJO我在下面放了一个SSCCE.真正引起很大兴趣的唯一部分是在EventBus循环中发生的转换.

public class Test {    public static voID main(String[] args) throws InterruptedException {        //create the thread to demonstrate execution        MyThread t = new MyThread();        //add a non activity observer        t.addobserver(new NonActivityObserver());        //add an activity observer        t.addobserver(new ActivityDecendent());        //fire off the thread        new Thread(t).start();        //give us time to read the output        Thread.sleep(Long.MAX_VALUE);           }    public static class MyThread implements Runnable    {        private ArrayList<Observer> List = new ArrayList<Observer>();        public voID addobserver(Observer arg0) {            synchronized (List) {                List.add(arg0);            }        }        @OverrIDe        public voID run()        {            //no loop just doing this once for example           synchronized(List)           {               for(final Observer o : List) {                   //first try to cast to an Activity                   try {                       Activity act = (Activity)o;                       //if we get here, its an activity                        //so invoke on its UiThread                       act.runOnUiThread(new Runnable() {                        @OverrIDe                        public voID run() {                            Event event = new Event("From the activity's runOnUiThread method");                            o.handleEvent(event);                        }                       });                   }                   catch (Exception e) {                       //if we got here, the class is not an activity                       //so it should be safe to just handle the event                       //on this thread                       Event event = new Event("From observers handle event method");                       o.handleEvent(event);                   }                  }                                 }         }      }    //your observer interface    public static interface Observer {        public voID handleEvent(Event e);    }    //Your Event class    public static class Event {        private String message;        public Event(String message) {            this.message = message;        }        public voID talk() {            System.out.println(message);        }    }    //An observer which isnt an activity    public static class NonActivityObserver implements Observer {        @OverrIDe        public voID handleEvent(Event e) {            e.talk();        }    }    //An activity which implements Observer    public static class ActivityDecendent extends Activity implements Observer {        @OverrIDe        public voID handleEvent(Event e) {            e.talk();        }    }    //An Activity     public static class Activity {        //pretend this is the AndroID activity executing this runnable        //on the UI thread        public voID runOnUiThread(Runnable r) {            new Thread(r).start();        }    }}

并输出：

From observers handle event methodFrom the activity's runOnUiThread method

这个解决方案特定于你的情况,这很糟糕……但我认为这应该有效.

总结

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