Java中的匿名类扩展线程 [英] Anonymous class extending thread in Java

问题描述

这是Java语法问题，但仅出于某些背景.

This is a Java syntax question, but just for some background.

使用android，我创建了一个很小的应用程序，运行非常缓慢，并且经常崩溃，因为单击按钮时，onClick()方法更改了各种按钮的按钮图像.这确实很笨拙而且很慢，我在网上搜索后发现问题很普遍，并且当在onClick()方法中更改许多图像时，最好将它们放在单独的线程中.还有一个好心的人为此提供了代码.

Using android, I created a small app that went really slow and often crashed because when a button was clicked the onClick() method changed button images for various buttons. It was really clunky and slow and I found out after a search on the net that the problem is pretty common, and when changing lots of images in the onClick() method, its best to put them in a separate thread. And some kind person gave the code for doing this.

new Thread(new Runnable() {
                public void run() {
                    quest.post(new Runnable() {
                        public void run() {
                            correct = nextQ();

                        }
                      });

                    }

                  }).start();

nextQ()方法和"quest" TextView是我的.这与我的问题做什么无关紧要，但是nextQ进行数据库搜索并更新图像，并且在线程外运行它确实很慢且很麻烦. 现在，我将此代码复制并粘贴到我的代码中，并且运行良好.一个快乐的结局.但是我不习惯使用我不理解的代码.而且我不太了解Java.因此，我尽了最大的努力研究匿名内部类，但是我仍然对代码感到困惑.

The nextQ() method and the "quest" TextView are mine. It's not really relevant to my question what they do, but nextQ does a database search and updates images, and running it outside the thread is really slow and crashy. Now I copied and pasted this code into my code and it runs fine. A happy ending. But I dont feel comfortable using code I don't understand. And I don't know Java very well. SO I researched as best I could anonymous inner classes, but I'm still stumped by the code.

因此，匿名类扩展了线程，并且它的参数使用了一个匿名类，实现了可运行的，其中放置了代码的肉". 问题: 1)我为什么要这样做?我可以理解使用线程OR可运行，但是为什么要一起使用呢? 2)如何运作?我回到了线程和可运行的基础知识，但是我看不到您如何以这种方式一起使用它们.

So the anonymous class extends thread, and as it's argument uses an anonymous class, implementing runnable, in which the "meat" of the code is placed.. Questions: 1)Why would I do this? I can understand using thread OR runnable, but why together? 2)How does this work? I went back to basics of thread and runnable, but I don't see how you use them together this way.

推荐答案

• 您正在创建Runnable接口的匿名实现
• 您正在将该实现传递给Thread类的构造函数.因此，您无需扩展Thread，而只需实例化它，并传递一个参数即可.
然后
• 您start()线程.因此，传递的参数的run()方法将在新线程中调用.
• you are creating an anonymous implementation of the Runnable interface
• you are passing that implementation to the constructor of the Thread class. So you are not extending Thread, you are just instantiating it, and pass an argument.
• you then start() the thread. Thus the run() method of the passed argument will be invoked in a new thread.

您需要这样做，因为:

• Runnable定义执行的内容
• Thread实际上执行它.
• the Runnable defines what gets executed
• the Thread actually executes it.

您的困惑是可以理解的，因为Thread也是Runnable.这就是为什么在Java 5中执行器框架被引入，它将执行机制(执行程序)与执行的代码(Runnable或Callable)分开.

Your confusion is understandable, since a Thread is also Runnable. That's why in Java 5 the executors framework was introduces, which separated the execution mechanism (an executor) from the executed code (Runnable or Callable).

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