初始化LayoutInflater期间上下文的NullPointerException

Question

我通过API获取数据并尝试将它们放在ListView中（我先将它们包装在一个包中），我使用的是BaseAdapter。问题是我在片段内传递给适配器的Context / LayoutInflater返回一个NullPointer异常

// AsyncTask中的onPostExecute

@Override
    protected void onPostExecute(Bundle bundle) {
        if(bundle != null){
            ResultFragment resultFragment = new ResultFragment();
            resultFragment.asyncExecuted(bundle);
        }
    }

// Fragment中的方法

public void asyncExecuted(Bundle bundle) {
        listResult.setAdapter(new ResultAdapter(bundle,getActivity()));
    }

//适配器类，错误在Adapter类上，专门用于初始化inflater 。

public class ResultAdapter extends BaseAdapter {
    String title, isbn, author;
    String[] s_title, s_isbn, s_rating, s_image, s_author;
    LayoutInflater inflater;

    public ResultAdapter(Bundle bundle, Context context){
        inflater  = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        try {
            title = bundle.getString("M_TITLE");
            isbn = bundle.getString("M_ISBN_13");
            author = bundle.getString("M_AUTHOR_NAME");

            int size = bundle.getInt("M_SIMILAR_SIZE");
            s_title = new String[size];
            s_isbn = new String[size];
            s_rating = new String[size];
            s_image = new String[size];
            s_author = new String[size];

            s_title = bundle.getStringArray("M_SIMILAR_TITLE");
            s_isbn = bundle.getStringArray("M_SIMILAR_ISBN_13");
            s_rating = bundle.getStringArray("M_SIMILAR_RATING");
            s_image = bundle.getStringArray("M_SIMILAR_IMAGE_URL");
            s_author = bundle.getStringArray("M_SIMILAR_AUTHOR_NAME");
        }catch (NullPointerException e){
            Log.e(getClass().getSimpleName(),"Nothing is Inside!");
        }
    }

    @Override
    public int getCount() {
        return s_title.length;
    }

    @Override
    public Object getItem(int position) {
        return s_isbn[position];
    }

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View row = inflater.inflate(R.layout.list_item_result, parent, false);
        TextView txtTitle = (TextView)row.findViewById(R.id.txtTitle);
        TextView txtAuthor = (TextView)row.findViewById(R.id.txtAuthor);
        TextView txtRating = (TextView)row.findViewById(R.id.txtRating);

        txtTitle.setText(s_title[position]);
        txtAuthor.setText(s_author[position]);
        txtRating.setText(s_rating[position]);

        return row;
    }
}

LOGCAT错误条目

Answer 1

创建Fragment时，在onAttach(Activity)被调用之前，它尚未附加到Activity - 在此之前，getActivity()将返回null

您应该通过setArguments()将Bundle传递到Fragment，然后通过getArguments()检索，并在asyncExecuted中执行onAttach()方法}或稍后的fragment lifecycle。

Answer 2

检查标题和其他变量是否存在于Api中

使用try和catch方法添加代码。

try{
title = bundle.getString("M_TITLE"); isbn = bundle.getString("M_ISBN_13"); author = bundle.getString("M_AUTHOR_NAME"); }catch(...){}

Answer 3

1）通过检查getActivity（）是否为null，您应该在调用onPostExecute时验证您的片段是否仍附加到活动。如果为null，则片段已分离。在这种情况下，您通常想要退出。

2）如果它是getActivity的有效实例，请尝试：

View row = LayoutInflater.from(getContext()).inflate(R.layout.list_item_result, parent, false);