在Android中使用AQuery

Question

我需要在我的Android项目中使用AQuery，以便对服务器进行异步调用。我只需要调用服务器，当它给我数据时，我就用这些数据更新视图。因此，我在AsyncTask中编写异步调用。下面你可以看到我所做的:

public class Tab1Fragment extends Fragment implements OnItemClickListener {
    private ListView categorieListView ; 
    private ArrayAdapter<String> listAdapterCategorie ;
    private AQuery aq;
    private String[] lista = null;
    private ProgressDialog pDialog;
    private String nome_categoria;
    private int[] arrayID = null;
    ArrayList<String> planetList;
    JsonRequestActivity categoryAjax;
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        pDialog = new ProgressDialog(getActivity());
        LinearLayout view = (LinearLayout) inflater.inflate(R.layout.tab1, container, false);
        aq = new AQuery(this.getActivity(), view);                       
        categorieListView = (ListView) view.findViewById(R.id.listView1);        
        //new FetchMyDataTask(this.getActivity(), new FetchMyDataTaskCompleteListener(listAdapterCategorie, categorieListView, this.getActivity()), aq).execute("InputString");
        if(lista == null){
            new AggiornaLista().execute();
        }else{
            listAdapterCategorie = new ArrayAdapter<String>(getActivity().getApplicationContext(), R.layout.categoriegenerali, R.id.nomeAttivita, lista);
            categorieListView.setAdapter( listAdapterCategorie );
        }
        categorieListView.setOnItemClickListener(this);
        return view;
    }

    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position,
            long id) {
        Intent esercizioScelto = new Intent(this.getActivity(), CategoriaScelta.class);
        nome_categoria = categorieListView.getItemAtPosition(position).toString();
        esercizioScelto.putExtra("nome_categoria", nome_categoria);
        esercizioScelto.putExtra("id_categoria", arrayID[position]);
        startActivity(esercizioScelto);   
    }             
    private class AggiornaLista extends AsyncTask<String, Void, String[]>{
        @Override
        protected void onPreExecute(){
            super.onPreExecute();
            pDialog.setMessage("Caricamento dati server");                  
        }
        @Override
        protected String[] doInBackground(String... params) {
            String url = Const.URL_JSON_ARRAY;
            Map<String, String> params2 = new HashMap<String, String>();
            params2.put("type", "get_all");
            aq.ajax(url, params2, JSONArray.class, new AjaxCallback<JSONArray>() {                                                
                @Override
                public void callback(String url, JSONArray json, AjaxStatus status) {
                    if(json != null){
                        lista = new String[json.length()];
                        arrayID = new int[json.length()];
                        for(int i = 0; i < json.length(); i++){
                            try {
                                lista[i] = result.getJSONObject(i).getString("Name");
                                arrayID[i] = result.getJSONObject(i).getInt("ID");
                            } 
                            catch (JSONException e) {
                                // TODO Auto-generated catch block
                                e.printStackTrace();
                            }
                        }
                        //Toast.makeText(aq.getContext(), jsonArray.toString(), Toast.LENGTH_LONG).show();
                    }else{                              
                        //ajax error, show error code
                        //Toast.makeText(aq.getContext(), "Error:" + status.getCode(), Toast.LENGTH_LONG).show();
                    }
                    // do something with the result                             
                }
            });       
            return lista;
        }
        @Override
        protected void onPostExecute(String result[])
        {
            super.onPostExecute(result);
            pDialog.dismiss();
            listAdapterCategorie = new ArrayAdapter<String>(getActivity().getApplicationContext(), R.layout.categoriegenerali, R.id.nomeAttivita, result);
            // Set the ArrayAdapter as the ListView's adapter. 
            categorieListView.setAdapter( listAdapterCategorie );
        }
    }
}

这个实现没有像我预期的那样工作。事实上，在onPostExecute中，doInBackground返回的参数没有更新，它包含初始化值(null)。然后我只在AsyncTask:

中改变了一些东西。

private class AggiornaLista extends AsyncTask<String, Void, Void>
    {
        @Override
        protected void onPreExecute()
        {
            super.onPreExecute();
            pDialog.setMessage("Caricamento dati server");
        }
        @Override
        protected Void doInBackground(String... params) {
            String url = Const.URL_JSON_ARRAY;
            Map<String, String> params2 = new HashMap<String, String>();
            params2.put("type", "get_all");
            aq.ajax(url, params2, JSONArray.class, new AjaxCallback<JSONArray>() {                                                
                @Override
                public void callback(String url, JSONArray json, AjaxStatus status) {
                    if(json != null){
                        lista = new String[json.length()];
                        arrayID = new int[json.length()];
                        for(int i = 0; i < json.length(); i++){
                            try {
                                lista[i] = result.getJSONObject(i).getString("Name");
                                arrayID[i] = result.getJSONObject(i).getInt("ID");
                            } catch (JSONException e) {
                                // TODO Auto-generated catch block
                                e.printStackTrace();
                            }
                        }
                        //Toast.makeText(aq.getContext(), jsonArray.toString(), Toast.LENGTH_LONG).show();
                    }else{                              
                        //ajax error, show error code
                        //Toast.makeText(aq.getContext(), "Error:" + status.getCode(), Toast.LENGTH_LONG).show();
                    }
                    // do something with the result                             
                    listAdapterCategorie = new ArrayAdapter<String>(getActivity().getApplicationContext(), R.layout.categoriegenerali, R.id.nomeAttivita, lista);
                    // Set the ArrayAdapter as the ListView's adapter. 
                    categorieListView.setAdapter( listAdapterCategorie );
                }
            });       
            return null;
        }
        @Override
        protected void onPostExecute(Void result)
        {
            super.onPostExecute(result);
            pDialog.dismiss();
        }
    }

这样做，用户界面是正确更新的，但我认为这不是正确的方法。那么，我能做什么呢?谢谢。

Andrea

Answer 1

如果我没有弄错的话，您目前正在异步任务中包装异步任务。您的aq.ajax(...)正在启动一个新线程来进行调用，然后调用您定义的callback(...)。AsyncTask执行doInBackground()，启动另一个任务。在ajax调用完成之前，doInBackground()方法完成。因此，onPostExecute()在ajax调用完成之前被执行。

解决方案是省略整个AsyncTask结构。只要在主onCreateView中调用aq.ajax()，当调用在您定义的回调中返回时，做您必须做的事情。(基本上把doInBackGround()的内容放在主

Answer 2

感谢您的回复。根据您的建议，我创建了一个示例项目:基本上，它只有一个文本视图，显示由服务器传递的字符串值。这是主要活动，也是项目中唯一的活动:

public class MainActivity extends Activity {
    private AQuery aq;
    private String serverParameter = "";
    private TextView myTextView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        myTextView = (TextView)findViewById(R.id.myTextView);
        aq = new AQuery(this);
        asyncCall();
        myTextView.setText(serverParameter);        
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
    private void asyncCall(){
        String url = "http://tryourweb.altervista.org/LocalOfferte0.0/src/category_controller.php";
        Map<String, String> params = new HashMap<String, String>();
        params.put("type", "get_all");
        aq.ajax(url, params, JSONArray.class, new AjaxCallback<JSONArray>() {
            @Override
            public void callback(String url, JSONArray json, AjaxStatus status) {
                if(json != null){
                    //successful ajax call, show status code and json content
                    try {
                        Toast.makeText(aq.getContext(), status.getCode() + ":" + json.getJSONObject(0).getString("Name"), Toast.LENGTH_LONG).show();
                        serverParameter = json.getJSONObject(0).getString("Name");
                    } catch (JSONException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }else{  
                    //ajax error, show error code
                    Toast.makeText(aq.getContext(), "Error:" + status.getCode(), Toast.LENGTH_LONG).show();
                }
            }
        });     
    }
}

遗憾的是，setText设置了初始化值。怎么解呢?再次感谢你。

Andrea