setOnCheckedChangeListener参数 [英] setOnCheckedChangeListener arguments

问题描述

    RadioGroup radioGroup = (RadioGroup) findViewById(R.id.orientation);
    radioGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener()
    {
        public void onCheckedChanged(RadioGroup group, int checkedId) {
            switch (checkedId) {
                case R.id.horizontal:
                    group.setOrientation(LinearLayout.HORIZONTAL);
                    break;
                case R.id.vertical:
                    group.setOrientation(LinearLayout.VERTICAL);
                    break;
            }
        }
    });

什么是radioGroup.setOnCheckedChangeListener？这是一种方法吗？那么它的论点是什么？

What is radioGroup.setOnCheckedChangeListener eactly? Is it a method? What are it's arguments then?

推荐答案

setOnCheckedChangeListener（）是一种方法它设置一个监听器，用于监听特定的操作。

setOnCheckedChangeListener() is a method which sets a listener which listens on a specific action.

这个想法是这样的：

1. 你想要单选按钮当用户更改选择时执行某些操作。

1. You want the radio button to perform some action when the user changes the selection.

只要选择更改，系统就会告诉单选按钮。如果单选按钮具有侦听器集，则侦听器侦听该事件 - 有一种机制通过调用其方法执行某些操作 onCheckedChanged（）

The system tells the radio button whenever the selection has been changed. If the radio button have a listener set, the listener "listens" to the event - there is a mechanism which performs some action by calling its method onCheckedChanged()

您应该意识到事件发生时会调用 onCheckedChanged（），而不是在侦听器时传递给 setOnCheckedChangeListener（）方法 - 所以在调用代码示例时不会！

You should realize that the onCheckedChanged() is called in the moment the event happens, not at the time the listener is passed to the setOnCheckedChangeListener() method - so not at the time of your code example is called!

类新的RadioGroup.OnCheckedChangeListener（）需要传递监听器的行为 - 最多包含Java 7，你不能只传递一个方法没有上课。从Java 8开始，您可以使用 lambda表达式轻松完成它。 ，但现在不要理会它。

The class new RadioGroup.OnCheckedChangeListener() is needed to pass the listener's behaviour - up to Java 7 inclusive, you cannot pass just a method without a class. Since Java 8 you may do more easily it using lambda expressions, but don't bother with it now.

这是一个非常高级的话题，我建议你研究这个第一个：

This is quite an advanced topic, I recommend you to study this first:

• 监听器设计模式（又名观察者）


• 匿名类

• Listener design pattern (a.k.a. Observer)
• Anonymous classes

您可以用简化的方式考虑它。您的代码具有以下含义：

You may think about it in the simplified way. Your code has the following meaning:

亲爱的 radioGroup ，
$ b每当检查更改时你应该做的事情是：

Dear radioGroup,
the thing which you should do whenever the check has been changed is this:

• 如果选择水平，
  
  致电 group.setOrientation（LinearLayout.HORIZONTAL）


• 如果选择垂直，
  
  电话 group.setOrientation（LinearLayout.VERTICAL）

• if "horizontal" has been selected,
  call group.setOrientation(LinearLayout.HORIZONTAL)
• if "vertical" has been selected,
  call group.setOrientation(LinearLayout.VERTICAL)

NB 不要这样做现在，只有当检查更改时才

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