AsyncTask，HttpClient和ProgressDialog

Question

我正在創建一個AsyncTask來將用戶登錄到服務器。 登錄工作正常，但是ProgressDialog直到過程結束才顯示。 用戶點擊按鈕后，UI就會凍結，並且我的對話框不會顯示。

我感謝任何幫助。 這是我的代碼。

public class MyApp extends Activity {
    private ProgressDialog dialogo = null;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Button loginButton = (Button) findViewById(R.id.btnLogin);
        loginButton.setOnClickListener(new View.OnClickListener() {

            public void onClick(View v) {
                SharedPreferences preferencias = PreferenceManager.getDefaultSharedPreferences(getBaseContext());
                String webAddress = preferencias.getString("webAddress", "");

                if (webAddress.isEmpty()) {
                    Toast.makeText(getBaseContext(), "Please, configure a Web Address.", Toast.LENGTH_LONG).show();
                } else {
                    EditText edtUsername = (EditText) findViewById(R.id.edtUsername);
                    EditText edtPassword = (EditText) findViewById(R.id.edtPassword);

                    HashMap<String, String> parametros = new HashMap<String, String>();
                    parametros.put("username", edtUsername.getText().toString());
                    parametros.put("password", edtPassword.getText().toString());

                    Requisicao requisicao = new Requisicao(parametros);
                    AsyncTask<String, Void, String> resposta = requisicao.execute(webAddress + "/login");

                    try {
                        Toast.makeText(getBaseContext(), resposta.get(), Toast.LENGTH_LONG).show();
                    } catch (InterruptedException e) {
                        Toast.makeText(getBaseContext(), "InterruptedException (login)", Toast.LENGTH_LONG).show();
                    } catch (ExecutionException e) {
                        Toast.makeText(getBaseContext(), "ExecutionException (login)", Toast.LENGTH_LONG).show();
                    }
                }
            }
        });

        ImageView engrenagem = (ImageView) findViewById(R.id.imgEngrenagem);
        engrenagem.setOnClickListener(new View.OnClickListener() {

            public void onClick(View v) {
                Intent preferenciasActivity = new Intent(getBaseContext(), Preferencias.class);
                startActivity(preferenciasActivity);
            }
        });
    }



    public class Requisicao extends AsyncTask<String, Void, String> {
        private final HttpClient clienteHttp = new DefaultHttpClient();
        private String resposta;
        private HashMap<String, String> parametros = null;

        public Requisicao(HashMap<String, String> params) {
            parametros = params;
        }

        @Override
        protected void onPreExecute() {
            dialogo = new ProgressDialog(MyApp.this);
            dialogo.setMessage("Aguarde...");
            dialogo.setTitle("Comunicando com o servidor");
            dialogo.setIndeterminate(true);
            dialogo.setCancelable(false);
            dialogo.show();
        }

        @Override
        protected String doInBackground(String... urls) {
            byte[] resultado = null;
                HttpPost post = new HttpPost(urls[0]);
            try {
                ArrayList<NameValuePair> paresNomeValor = new ArrayList<NameValuePair>();
                Iterator<String> iterator = parametros.keySet().iterator();
                while (iterator.hasNext()) {
                    String chave = iterator.next();
                    paresNomeValor.add(new BasicNameValuePair(chave, parametros.get(chave)));
                }

                post.setEntity(new UrlEncodedFormEntity(paresNomeValor, "UTF-8"));

                HttpResponse respostaRequisicao = clienteHttp.execute(post);
                StatusLine statusRequisicao = respostaRequisicao.getStatusLine();
                if (statusRequisicao.getStatusCode() == HttpURLConnection.HTTP_OK) {
                    resultado = EntityUtils.toByteArray(respostaRequisicao.getEntity());
                    resposta = new String(resultado, "UTF-8");
                }
            } catch (UnsupportedEncodingException e) {
            } catch (Exception e) {
            }
            return resposta;
        }

        @Override
        protected void onPostExecute(String param) {
            dialogo.dismiss();
        }
    }
}

Answer 1

嘗試在按鈕偵聽器中注釋掉resposta.get()調用。 我猜它只是阻塞了主UI線程，直到任務完成。

Answer 2

幾件事。 首先，不要為ASyncClass創建實例，因為根據android文檔，您只能調用一次。 這樣執行： new Requisicao().execute(webAddress + "/login");

另外，不要調用requisicao.get() ，這將再次根據文檔“等待以完成計算，然后檢索其結果”（也稱為阻塞），從您的異步類中添加重寫：

protected void onProgressUpdate(Long... progress) {
    CallBack(progress[0]); // for example
}

其中CallBack是UI線程中的一個函數，它將長時間處理進程，字符串，或其他任何您想回退的進程。 提醒您，您的ASync類將必須在UI類中定義，而不是單獨定義。

Answer 3

移動你的

  private ProgressDialog dialogo = null;

就像使用HTTPClient一樣進入AsyncTask的字段，因為您似乎沒有在任何地方使用它並嘗試在構造函數中創建對話框

public Requisicao(HashMap<String, String> params) {
            parametros = params;
          dialogo = new ProgressDialog(MyApp.this);
        }

在postExecute中

 if (dialogo .isShowing()) {
                dialogo .dismiss();
 }

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希望能幫助到你。