为什么我想避免片段中的非默认构造函数? [英] Why do I want to avoid non-default constructors in fragments?

问题描述

我正在使用 Fragments 创建一个应用程序，在其中一个应用程序中，我创建了一个非默认构造函数并收到此警告:

I am creating an app with Fragments and in one of them, I created a non-default constructor and got this warning:

Avoid non-default constructors in fragments: use a default constructor plus Fragment#setArguments(Bundle) instead

谁能告诉我为什么这不是一个好主意?

Can someone tell me why this is not a good idea?

你能否建议我如何实现这一点:

Can you also suggest how I would accomplish this:

public static class MenuFragment extends ListFragment {
    public ListView listView1;
    Categories category;

    //this is my "non-default" constructor
    public MenuFragment(Categories category){
        this.category = category;
    }....

不使用非默认构造函数?

Without using the non-default constructor?

推荐答案

制作一个 bundle 对象并插入你的数据(在这个例子中是你的 Category 对象).请注意，您不能将此对象直接传递到包中，除非它是可序列化的.我认为最好在片段中构建您的对象，并且只将一个 id 或其他东西放入包中.这是创建和附加包的代码:

Make a bundle object and insert your data (in this example your Category object). Be careful, you can't pass this object directly into the bundle, unless it's serializable. I think it's better to build your object in the fragment, and put only an id or something else into bundle. This is the code to create and attach a bundle:

Bundle args = new Bundle();
args.putLong("key", value);
yourFragment.setArguments(args);

之后，在您的片段中访问数据:

After that, in your fragment access data:

Type value = getArguments().getType("key");

仅此而已.

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