无法解析ListView适配器中的getSystemService方法

问题描述

我正在研究John Horton的 Android初学者编程，目前正在尝试创建一个笔记应用程序。 Horton刚刚推出了 ListViews 。但是，我在使用适配器 类时遇到问题：

I am working through John Horton's Android Programming for Beginners, and am currently attempting to create a note-taking app. Horton has just introduced ListViews. However, I am having trouble with the adapter class:

public class NoteAdapter extends BaseAdapter {

    List<Note> mNoteList = new ArrayList<Note>(); 

    @Override
    public int getCount(){
        return mNoteList.size();
    }

    @Override
    public Note getItem(int whichItem){
        return mNoteList.get(whichItem);
    }

    @Override
    public long getItemId(int whichItem){
        return whichItem;
    }

    @Override
    public View getView(int whichItem, View view, ViewGroup viewGroup){

        // check if view has been inflated already
        if (view == null){
            LayoutInflater inflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE); // ERROR HERE

            view = inflater.inflate(R.layout.listitem, viewGroup, false);

        }

        return view;
    }

}

问题出在 getView 方法，我试图膨胀 布局： Android Studio会抛出错误：'无法解析getSystemService（java.lang.String）'。

The problem is in the getView method, where I'm attempting to inflate the layout: Android Studio throws an error: 'Cannot resolve getSystemService(java.lang.String)'.

完整新手只是通过这本书我不知道从哪里去或者试图解决它 - 有人可以帮忙吗？

As a complete newcomer just following through the book I have no idea where to go from here or what to try to resolve it - can anyone help?

推荐答案

LayoutInflater 的最佳方法是在活动上调用 getLayoutInflater（） 。这样，活动的主题就被考虑在内了。如果 NoteAdapter 是在活动中定义的，只需调用 getLayoutInflater（）。如果 NoteAdapter 在其自己的单独Java类文件中定义，则通过构造函数传入 LayoutInflater 。

The best way to get a LayoutInflater is by calling getLayoutInflater() on an Activity. That way, the activity's theme is taken into account. If NoteAdapter is defined inside of an Activity, just call getLayoutInflater(). If NoteAdapter is defined in its own separate Java class file, pass in a LayoutInflater via the constructor.

要更直接地解决您的问题，任何查看，例如 ListView ，可以调用 getContext（）来获取上下文。这就是定义 getSystemService（）的地方。因此，用 viewGroup.getContext（）替换 getSystemService（） .getSystemService（）将起作用。

To more directly address your question, any View, like ListView, can call getContext() to get a Context. That is where getSystemService() is defined. So, replacing getSystemService() with viewGroup.getContext().getSystemService() would work.

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