如何在Android中实现回调? [英] How to realize a callback in android?

问题描述

也许我对这个主题的了解很小，以至于"callback"一词不正确，对此感到抱歉.

Maybe my knowledge about this topic is so small, that the word "callback" is not right here, sorry about that.

如果我在任何类/活动/其他线程中启动一个线程，并在完成后希望它从启动该线程的实例(类/活动/其他线程)中执行其他代码，那么我如何实现呢?

If I start an thread in any class/activity/other thread and after finishing I want it to execute some other code from the instance (class/activity/other thread) which started the thread, how do I realize that?

目前，我是这样的:

这里是伪代码.

// Method inside class/activity/other thread
private void startThread(){
    MyThread thread = new MyThread(this);
    thread.start();
}

在线程内

public class MyThread extends Thread{
    private (class/activity/other thread) instanceAbove;

    public MyThread ( (class/activity/other thread) instanceAbove){
        this.instanceAbove = instanceAbove;
    }

    public void run(){
        //Do some stuff
        finish();
    }

    public void finish(){
        instanceAbove.MyThreadFinishMethod();
    }

}

我认为这不是一个好方法，但是您能举个例子吗?

I think this is not a good way, but can you give me an example?

使用接口可用于AlertDialog，因为我可以使用onAppend().但是，在这种情况下，我不知道如何使用它们.

Using interfaces is working for AlertDialogs, because I can use onAppend(). However, in this case, I don't know how I could use them.

推荐答案

您可以轻松地使用interface并相应地从调用活动/类/其他线程中处理回调.这是一个例子.

You can easily use an interface and handle the callback accordingly from your calling activity/class/other thread. Here is an example.

首先定义一个类似于以下内容的接口.

Define an interface like the following first.

public interface ThreadFinishListener {
    void onFinish();
}

让我们假设您正在从Activity实例化Thread.因此，像下面这样在您的Activity中实现侦听器.

Let us assume you are instantiating a Thread from an Activity. Hence implement the listener in your Activity like the following.

public class MainActivity extends AppCompatActivity implements ThreadFinishListener {
    // .... Other functions in your activity 

    @Override
    void onFinish() {
        // Do something when the Thread is finished and returned back to the activity
        // This is actually your callback function. 
    }
}

现在修改Thread类的构造函数，以便可以将侦听器传递给它.

Now modify the constructor of your Thread class so that you can pass the listener to it.

public class MyThread extends Thread {
    private ThreadFinishListener listener; 

    public MyThread(ThreadFinishListener listener){
       this.listener = listener;
    }

    public void run(){
        //Do some stuff
        finish();
    }

    public void finish() {
        // This will invoke the function call in your activity
        listener.onFinish();
    }
}

现在，在初始化Thread时，您可能希望按以下方式将侦听器传递给它.

Now while initializing your Thread, you might want to pass the listener to it as follows.

MyThread thread = new MyThread(this);
thread.run();

我希望足够.

这篇关于如何在Android中实现回调?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！