Androids Handler.post，究竟会发生什么 [英] Androids Handler.post, what happens exactly

问题描述

几天以来，我试图弄清楚如果我在

since several days, I tried to figure out what exactly happens if I execute code in

void function(){

  //somePreExecutionCode
  new Handler().post(new Runnable(){
    @Override 
    public void run(){
       //someCode
    }
  });
}

似乎并没有阻塞UI，因此，在someCode完成之前，调用function()的按钮不会停留在单击位置. 但是，如果somePreExecutionCode启动progressBar，则someCode完成后的同一时刻将显示progressBar. 我知道，有AsyncTasks用于，但是还有其他可能性吗?

It seems like it isn't blocking the UI, so buttons, which calls function() doesn't stuck in the clicked position until someCode has finished. But if somePreExecutionCode starts a progressBar, the progressBar is shown at exactly the same moment, when someCode has finished. I know, there are AsyncTasks for, but is there any other possibility?

和

new Handler().post 

和

View.post

?

推荐答案

简单地说，有 Looper线程，例如 UI线程.这样的线程具有自己的 Looper ，该线程为该线程运行消息循环.

Putting it simply, there are Looper threads, for example, UI thread. Such thread has its own Looper, which runs a message loop for the thread.

此类线程通常具有 Handler ，该线程对其进行处理Looper的消息-覆盖public void handleMessage(Message msg)或执行Runnable，该消息已发布到其循环程序的消息队列中.

Such thread, typically, has a Handler, which processes its Looper's messages - overriding public void handleMessage(Message msg) or executing a Runnable, which was posted to it's looper's message queue.

当您在 UI线程的上下文中创建Handler时(就像您在代码中所做的那样)，它与 UI线程的循环程序相关联，因此您的\\someCode在 UI线程上运行.

When you're creating a Handler in the context of UI thread (like you did in your code), it gets associated with UI thread's looper, so your \\someCode runs on UI thread.

我想，在您的用例中，new Handler().post(Runnable)和View:post(Runnable)几乎是相同的，因为它们都在 UI线程消息队列中添加了Runnable.

I guess, in your use case new Handler().post(Runnable) and View:post(Runnable) are mostly the same, as they both add a Runnable to the UI thread message queue.

但是它们并不相同.

• View:post(Runnable)将在 UI线程循环程序的消息队列中添加Runnable；
• Handler:post(Runnable)会将Runnable添加到其关联的线程循环程序的消息队列

• View:post(Runnable) will add a Runnable to the UI thread looper's message queue;
• Handler:post(Runnable) will add a Runnable to its associated thread looper's message queue

我的解释非常直观，所以如果我错了，请纠正我.

My explanation is pretty much intuitive, so correct me anyone if I am wrong.

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