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) {
}
}

它以前在主线程中工作，但速度很慢，所以我想到了使用Asynctask，但我对此很陌生，网上的教程也不清楚，所以有人能告诉我这里面出了什么问题，以及我如何在后台获取联系人而不会很慢。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。

Answer 1

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

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()