初始化 LayoutInflater 期间上下文出现 NullPointerException

Question

我正在通过 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），我正在使用 BaseAdapter。问题是 Context/LayoutInflater 我在一个片段中传递给适配器 returns 一个 NullPointer Exception

//AsyncTask中的onPostExecute

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

//Fragment里面的方法

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

//Adapter Class, Adapter class 错误，特别是初始化 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

检查标题和其他变量是否存在于Api

使用 try 和 catch 方法添加代码。

尝试{<br> 标题 = bundle.getString("M_TITLE"); isbn = bundle.getString("M_ISBN_13"); 作者 = bundle.getString("M_AUTHOR_NAME"); }赶上（...）{}

Answer 2

当您创建 Fragment 时，它尚未附加到 Activity 直到 onAttach(Activity) 被调用 - 直到那时，getActivity() 将 return null.

您应该通过 setArguments() and then retrieve it via getArguments(), and execute your asyncExecuted method in onAttach() or later in the fragment lifecycle 将您的 Bundle 传递到您的 Fragment。

Answer 3

1) 您应该通过检查 getActivity() 是否为 null 来验证在调用 onPostExecute 时您的片段是否仍附加到 activity。如果它为 null，则该片段已分离。在这种情况下你通常想退出。

2) 如果它是 getActivity 的有效实例，试试这个：

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

初始化 LayoutInflater 期间上下文出现 NullPointerException

NullPointerException on Context during Initializing LayoutInflater

android

android-context

layout-inflater