Question

我的申请表有问题。我的列表视图中填充了来自parse.com的数据，但是当用户未连接到互联网时，列表视图为空。当用户在线显示列表视图离线时，我没办法保存listview的适配器吗？

我尝试了各种方式并阅读了parse.com文档，但无济于事。这是我的代码。

public class Eventos extends ActionBarActivity {

    ListView listview;
    List<ParseObject> ob;
    ProgressDialog mProgressDialog;
    ListViewEventos adapter;
    private List<GetEventos> eventos_lista = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.eventos);

        new RemoteDataTask().execute();
    }

    // RemoteDataTask AsyncTask
    private class RemoteDataTask extends AsyncTask<Void, Void, Void> {
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            // Create a progressdialog
            mProgressDialog = new ProgressDialog(Eventos.this);
            // Set progressdialog title
            mProgressDialog.setTitle("Carregando Dados...");
            // Set progressdialog message
            mProgressDialog.setMessage("Aguarde...");
            mProgressDialog.setIndeterminate(false);
            // Show progressdialog
            mProgressDialog.show();
        }

        @Override
        protected Void doInBackground(Void... params) {
            // Create the array
            eventos_lista = new ArrayList<GetEventos>();
            try {
                // Localizando a classe noticias no parse.com
                ParseQuery<ParseObject> query = new ParseQuery<ParseObject>(
                        "Eventos");
                //colocando por ordem de data
                query.orderByAscending("Number");
                ob = query.find();
                for (ParseObject titulo : ob) {
                    // Localizando as imagens na coluna foto do parse
                    ParseFile image = (ParseFile) titulo.get("Foto");
                    ParseFile img = (ParseFile) titulo.get("FotoEvento");

                    GetEventos eventos = new GetEventos();
                    eventos.setTitulo((String) titulo.get("Titulo"));
                    eventos.setDescricao((String) titulo.get("Descricao"));
                    eventos.setTextoEvento((String) titulo.get("TextoEvento"));
                    eventos.setFoto(image.getUrl());
                    eventos.setFotoEvento(img.getUrl());
                    eventos_lista.add(eventos);
                }

            } catch (ParseException e) {
                Log.e("Error", e.getMessage());
                e.printStackTrace();
            }
            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            // Locate the listview in listview_main.xml
            listview = (ListView) findViewById(R.id.listViewEventos);
            // Pass the results into ListViewAdapter.java
            adapter = new ListViewEventos(Eventos.this,
                    eventos_lista);
            // Binds the Adapter to the ListView
            listview.setAdapter(adapter);
            // Close the progressdialog
            mProgressDialog.dismiss();
        }
    }    
}

Answer 1

Parse本身支持查询缓存和本地数据存储（在引擎盖下使用SQLite），它可以像以下一样简单：

final String TOP_SCORES_LABEL = "topScores";

// Query for the latest objects from Parse.
query.findInBackground(new FindCallback<ParseObject>() {
  public void done(final List<ParseObject> scoreList, ParseException e) {
    if (e != null) {
      // There was an error or the network wasn't available.
      return;
    }

    // Release any objects previously pinned for this query.
    ParseObject.unpinAllInBackground(TOP_SCORES_LABEL, scoreList, new DeleteCallback() {
      public void done(ParseException e) {
        if (e != null) {
          // There was some error.
          return;
        }

        // Add the latest results for this query to the cache.
        ParseObject.pinAllInBackground(TOP_SCORES_LABEL, scoreList);
      }
    });
  }
});

可以在Parse docs中找到更多信息，这一切都取决于您的应用至少在线一次。

Answer 2

也许您可以使用SQLite临时存储数据。

我经常使用的针对Android的SQLite库 1. ActiveAndroid
2. GreeDAO

从服务器检索数据，然后存储在本地数据库中的第一步。下一步检查设备是否已连接到互联网。

用户离线时使用parse.com填充listview

2 个答案: