通过构造函数传递参数 [英] Passing a parameter through constructor

问题描述

首先，我将简要介绍一些紧密耦合的类（尽管不是最坏的情况）：

First I will present a quick outline of a somewhat tightly coupled classes (though not the worst possible case):

class setUpGUI {

   ...
   JTextField output = new JTextField();
   ...
   CountTimer ct;
   ...

   public void setOtputText(String text) {
       output.setText(text);

   public startTimer() {
      ct = new CountTimer();
   }

   ...
}

class CountTimer implements ActionListener {

    private String text = "";
    private gui = new SetUpGUI();
    ...

    @Override
    public void actionPerformed(ActionEvent e) {
        ...
        gui.setOtputText(text);
        ...
    }

我的问题是关于第二个片段（在与第一个单独比较）：

My question is about the second snippet (in comparison with the first and on its own):

// functionally equivalent to com.google.gwt.user.client.ui.HasText
interface HasText {

    String getText();
    void setText(String text);

}

class setUpGUI {

   ...
   JTextField output = new JTextField();
   ...
   CountTimer ct;
   ...

   public void setOtputText(String text) {
       output.setText(text);

   public startTimer() {
      ct = new CountTimer(output);
   }

   ...
}

class CountTimer implements ActionListener {

    private String text = "";
    private HasText txtComp;
    ...

    CountTimer(txtComp) {
        ...
        this.txtComp = txtComp;
        ...
    }


    @Override
    public void actionPerformed(ActionEvent e) {
        ...
        txtComp.setText(text);
        ...
    }
}

我相信第二种设计可以视为松耦合，因为它不是使用 setter 而是通过构造函数传递引用，同时定义了自己的 HasText 接口（因为Swing似乎没有，而且我没有找到 JtextComponent 和 JLabel 具有 setText（）方法）。你同意吗？

I believe that the second design can be considered a loose coupling, since instead of using a setter it passes a reference through constructor and at the same time defines its own HasText interface (since Swing does not seem to have one and I didn't find a common parent of JtextComponent and JLabel that has setText() method). Would you agree?

通过构造函数传递参数的一般态度是什么？

What is the general attitude towards passing a parameter via constructor?

推荐答案

您的第二个示例将文本视图组件传递给实现 ActionListener 的类。相反，请考虑扩展 AbstractAction 允许集中处理动作事件。对于特定的文本组件， TextAction 提供对焦点文本组件和 Document 模型的访问> JTextComponent 进行监听。作为具体示例，请在此处和此处，此类预定义操作在整个 EditorKit 层次结构中使用。

Your second example passes a textual view component to a class that implements ActionListener. Instead, consider a class that extends AbstractAction to allow centralized handling of action events. In the particular case of a text component, TextAction provides access to the focused text component and the underlying Document model to which the JTextComponent listens. As concrete examples, outlined here and here, such pre-defined actions are used throughout the EditorKit hierarchy.

用于定期操作，例如响应计时器可能发生的情况，请考虑让 ActionListener 更新文本组件的 Document ；侦听视图将自动更新以响应。在这种情况下，侦听器的构造函数将收到对文本组件模型的引用。

For periodic actions, such as might occur in response to a timer, consider letting the ActionListener update the text component's Document; the listening view will update itself automatically in response. In this case, the listener's constructor would receive a reference to the text component's model.

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