异步任务未加载数据

Posted 2023-05-07

【中文标题】异步任务未加载数据

【英文标题】：Async task not loading data

【发布时间】：2019-04-02 14:27:11

【问题描述】：

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，所以我想使用Asynctask，但我是新手，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获取后台的联系人不会很慢...................................................... .....................

【参考方案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()

【讨论】：

加载大约需要 5 秒... UI 线程上的代码只需要大约 2... 我怎样才能使它更快，我认为在后台运行会使其更快

您可以在从后台加载数据时向用户显示progressDialog。当您在后台加载数据时，您的应用程序不会冻结。用户可以使用您的应用，但加载速度不会变快。