java - 异步任务未加载数据

Question

代码

    public class ContactSettings extends Fragment {
    private RecyclerView contactsList;
    private List<ContactsHelper> contacts = new ArrayList<>();
    private LinearLayoutManager linearLayoutManager;
    private ContactsAdapter mAdapter;
       View rootView;
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        rootView = inflater.inflate(R.layout.settings_contact, container, false);



        contactsList = (RecyclerView) rootView.findViewById(R.id.usersList);
        //Add the data first
        linearLayoutManager = new LinearLayoutManager(getActivity());
        //and then create a object and pass the lis
        mAdapter = new ContactsAdapter(contacts);

        contactsList.setHasFixedSize(true);
        contactsList.setLayoutManager(linearLayoutManager);
        contactsList.setAdapter(mAdapter);
        mAdapter.notifyDataSetChanged();

        COntacts runner = new COntacts();


        return rootView;
    }

    @Override
    public void onStart(){
        super.onStart();
    }

    private class COntacts extends AsyncTask<String, Void, String> {
        @Override
        protected String doInBackground(String... urls) {
            ContentResolver contentResolver = getActivity().getContentResolver();
            Cursor cursor = contentResolver.query(ContactsContract.Contacts.CONTENT_URI, null, null, null, ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME + " ASC");
            if (cursor != null) {
                if (cursor.getCount() > 0) {
                    while (cursor.moveToNext()) {
                        int hasPhoneNumber = Integer.parseInt(cursor.getString(cursor.getColumnIndex(ContactsContract.Contacts.HAS_PHONE_NUMBER)));
                        if (hasPhoneNumber > 0) {
                            String id = cursor.getString(cursor.getColumnIndex(ContactsContract.Contacts._ID));
                            String name = cursor.getString(cursor.getColumnIndex(ContactsContract.Contacts.DISPLAY_NAME));
                            Cursor phoneCursor = contentResolver.query(
                                    ContactsContract.CommonDataKinds.Phone.CONTENT_URI,
                                    null,
                                    ContactsContract.CommonDataKinds.Phone.CONTACT_ID + " = ?", new String[]{id},
                                    null);
                            if (phoneCursor != null) {
                                if (phoneCursor.moveToNext()) {
                                    String phoneNumber = phoneCursor.getString(phoneCursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER));

                                    contacts.add(new ContactsHelper(name, phoneNumber));
                                    phoneCursor.close();
                                }
                            }
                        }
                    }
                }
                cursor.close();
            }
            return "Download failed";
        }


        @Override
        protected void onPostExecute(String result) {
        }
    }

    public void onClick(View view) {

    }
}

它曾经在主线程中工作，但速度很慢，所以我想到使用Asynctask，但我对此很陌生，并且在线教程不清楚，所以有人可以告诉我这有什么问题以及如何在后台获取联系人而又不慢......................................................................................

Answer 1

正如我在代码中看到的，您没有在 doInBackground 中使用 urls 参数。并且您需要将 contacts 传递给在 UI Thread 中运行的 onPostExecute :

private class COntacts extends AsyncTask<Void, Void, List<ContactsHelper>> {

@Override
protected List<ContactsHelper> doInBackground(Void... urls) {
   List<ContactsHelper> contacts = new ArrayList<>();
   ...
   return contacts
}

@Override
protected void onPostExecute(List<ContactsHelper> result) {
    contacts.addAll(result);
    mAdapter.notifyDataSetChanged();
}

您需要在代码中执行runner对象:

runner.execute()