如何在 Android 中进行后台工作时使用 AsyncTask 显示 ProgressDialog？ [复制]
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【中文标题】如何在 Android 中进行后台工作时使用 AsyncTask 显示 ProgressDialog？ [复制]【英文标题】：How to use AsyncTask to show a ProgressDialog while doing background work in Android? [duplicate] 【发布时间】：2011-04-23 01:25:00 【问题描述】：可能重复：Updating progress dialog in Activity from AsyncTask
我正在开发我的第一个 android 应用程序，我需要在后台任务（在本例中只是服务器上的 http 调用）发生时显示 ProgressDialog。 我对此进行了一些研究，并且已经检查了与该主题相关的其他线程。
http://developer.android.com/reference/android/os/AsyncTask.html
Android show ProgressDialog until activity UI finished loading
Android SplashScreen
http://android-developers.blogspot.com/2009/05/painless-threading.html
等等。
比我写一点代码：
1) 在我的活动中，我声明一个变量为 ProgressDialog 类型
public class LoginActivity extends Activity
public static final String TAG = "LoginActivity";
protected ProgressDialog progressDialog;
...
2) 我还编写了一个内部类来根据需要扩展 AsyncTask，在 doInBackGround 中我调用了一个静态方法，该方法实际上对服务器执行 POST http 请求，在服务器端我阻止了服务器响应20 秒验证进度对话框。
class EfetuaLogin extends AsyncTask<Object, Void, String>
private final static String TAG = "LoginActivity.EfetuaLogin";
@Override
protected void onPreExecute()
Log.d(TAG, "Executando onPreExecute de EfetuaLogin");
@SuppressWarnings("unchecked")
@Override
protected String doInBackground(Object... parametros)
Log.d(TAG, "Executando doInBackground de EfetuaLogin");
Object[] params = parametros;
HttpClient httpClient = (HttpClient) params[0];
List<NameValuePair> listaParametros = (List<NameValuePair>) params[1];
String result = null;
try
result = HttpProxy.httpPost(AnototudoMetadata.URL_AUTENTICACAO, httpClient, listaParametros);
catch (IOException e)
Log.e(TAG, "IOException, Sem conectividade com o servidor do Anototudo! " + e.getMessage());
e.printStackTrace();
return result;
return result;
@Override
protected void onPostExecute(String result)
progressDialog.dismiss();
3）当按下按钮时，我会构建 ProgressDialog 并调用我创建的 AsyncTask：
OnClickListener loginListener = new OnClickListener()
public void onClick(View v)
//next line should start progress dialog in main thread ?????
progressDialog = ProgressDialog.show(LoginActivity.this, "Login in", "Wait a moment please", true, false);
//next couple of lines should do an ascyn call to server
EfetuaLogin efetuaLogin = new EfetuaLogin();
efetuaLogin.execute(params);
try
//recover the server response and sets time out to be 25seconds
sResposta = efetuaLogin.get(25, TimeUnit.SECONDS);
好吧，就是这样，我相信这是假设显示一个进度对话框，而 AsyncTask 将在后台查询服务器，但我得到的是在服务器响应到达之前没有进度条，而不是一小部分时间（更少超过 1 秒）进度显示并调用下一个 Activity。
正如我所提到的，我已经重新检查了这段代码，但根本找不到我出错的地方。 有什么建议吗？
提前谢谢你。
嗨，正如 Charlie Sheen(???) 在该线程的第一个答案中所建议的那样，我尝试更改了一些代码，现在它就像（不幸的是，到目前为止它没有按预期工作）：
OnClickListener loginListener = new OnClickListener()
public void onClick(View v)
//async call????????
new EfetuaLogin().execute(params);
...
然后在 AsyncTask 中完成所有处理响应的工作：
class EfetuaLogin extends AsyncTask<Object, Void, String>
private final static String TAG = "LoginActivity.EfetuaLogin";
@Override
protected void onPreExecute()
super.onPreExecute();
Log.d(TAG, "Executando onPreExecute de EfetuaLogin");
//inicia diálogo de progresso, mostranto processamento com servidor.
progressDialog = ProgressDialog.show(LoginActivity.this, "Autenticando", "Contactando o servidor, por favor, aguarde alguns instantes.", true, false);
@SuppressWarnings("unchecked")
@Override
protected String doInBackground(Object... parametros)
Log.d(TAG, "Executando doInBackground de EfetuaLogin");
Object[] params = parametros;
HttpClient httpClient = (HttpClient) params[0];
List<NameValuePair> listaParametros = (List<NameValuePair>) params[1];
String result = null;
try
result = HttpProxy.httpPost(AnototudoMetadata.URL_AUTENTICACAO, httpClient, listaParametros);
catch (IOException e)
Log.e(TAG, "IOException, Sem conectividade com o servidor do Anototudo! " + e.getMessage());
e.printStackTrace();
return result;
return result;
@Override
protected void onPostExecute(String result)
super.onPostExecute(result);
if (result == null || result.equals(""))
progressDialog.dismiss();
Alerta
.popupAlertaComBotaoOK(
"Dados incorretos",
"Os dados informados não foram encontrados no Sistema! Informe novamente ou cadastre-se antes pela internet.",
LoginActivity.this);
return;
Log.d(TAG, "Login passou persistindo info de login local no device");
ContentValues contentValues = new ContentValues();
contentValues.put(AnototudoMetadata.LOGIN_EMAIL, sLogin);
contentValues.put(AnototudoMetadata.LOGIN_SENHA, sSenha);
contentValues.put(AnototudoMetadata.LOGIN_SENHA_GERADA, result);
LoginDB loginDB = new LoginDB();
loginDB.addLogin(LoginActivity.this, contentValues);
Log.d(TAG, "Persistiu info de login no device, redirecionando para menu principal do Anototudo");
Log.d(TAG, "O retorno da chamada foi ==>> " + result);
// tudo ok chama menu principal
Log.d(TAG, "Device foi corretametne autenticado, chamando tela do menu principal do Anototudo.");
String actionName = "br.com.anototudo.intent.action.MainMenuView";
Intent intent = new Intent(actionName);
LoginActivity.this.startActivity(intent);
progressDialog.dismiss();
完成 OnClickListener：
OnClickListener loginListener = new OnClickListener()
public void onClick(View v)
Log.d(TAG, "Usuario logado, chamando menu principal");
TextView tLogin = (TextView) findViewById(R.id.loginText);
TextView tSenha = (TextView) findViewById(R.id.senhaText);
String sLogin = tLogin.getText().toString();
String sSenha = tSenha.getText().toString();
if (sLogin.equals("") | sSenha.equals(""))
Alerta.popupAlertaComBotaoOK("Campos Obrigatórios",
"Os campos Login e Senha são obrigatórios para autenticação do Anototudo.", LoginActivity.this);
return;
else
Pattern regEx = Pattern.compile(".+@.+\\.[a-z]+");
Matcher matcher = regEx.matcher(sLogin);
if (!matcher.matches())
Alerta.popupAlertaComBotaoOK("Formato e-mail inválido", "O formato do campo e-mail está inválido",
LoginActivity.this);
return;
List<NameValuePair> listaParametros = new ArrayList<NameValuePair>();
listaParametros.add(new BasicNameValuePair("login", sLogin));
listaParametros.add(new BasicNameValuePair("senha", sSenha));
Log.d(TAG, "valores recuperados dos campos de login e senha: " + sLogin + " | " + sSenha);
// Reutiliza cliente HttpClient disponibilizado pela Aplicação.
AnototudoApp atapp = (AnototudoApp) LoginActivity.this.getApplication();
HttpClient httpClient = atapp.getHttpClient();
//prepara lista de parametros para fazer chamada asíncrona no servidor para autenticar.
Object[] params = new Object[2];
params[0] = httpClient;
params[1] = listaParametros;
//faz chamada assincrona
new EfetuaLogin().execute(params);
;
【问题讨论】：
【参考方案1】：将您的ProgressDialog 放入onPreExecute，示例代码如下：
private ProgressDialog pdia;
@Override
protected void onPreExecute()
super.onPreExecute();
pdia = new ProgressDialog(yourContext);
pdia.setMessage("Loading...");
pdia.show();
@Override
protected void onPostExecute(String result)
super.onPostExecute(result);
pdia.dismiss();
在您的onClickListener 中，只需将这一行放在里面：
new EfetuaLogin().execute(null, null , null);
【讨论】：
我已经尝试过了（将 pd 放在 onPreExecute 中）也没有按预期工作。正如你提到的，我还需要传递一些参数来执行任务，所以我不能使用 execute(null)。我可以吗？请注意，我需要传递一些参数并从 AsyncTask 恢复响应，这就是我调用 AsyncTask.get 方法的原因。 @Marcos Maia：您创建了一个AsyncTask 的对象并在其中存储了一个引用。在不创建引用的情况下执行它。 AsyncTask 用于短操作，因此请检查onPostExecute 中的结果，而不是尝试通过您的参考获得响应。当您单击Button 时，无论如何您都无法获得服务器响应。
@Marcos Maia：将所有必要的东西放在doInBackground 中。来自doInBackground 的传出结果传递给onPostExecute 参数，在那里你可以检查你的服务器响应——所有这些都在AsyncTask 中。关于您传递给AsyncTask 的值，我无法告诉您任何事情，因为缺少一些代码 sn-ps。
@Charlie Sheen：我已经尝试过了，仍然有相同的行为。我将在此主题中发布另一个答案，显示代码的详细信息，因为 cmets 代码未格式化。感谢您的帮助，但仍然有一些缺失的部分，因为它到目前为止还没有工作。 :(
@Marcos Maia：编辑你的问题。【参考方案2】：
最终的解决方案是将所有代码从OnClickListener 转移到doInBackground 方法中的AsyncTask 实现。现在的代码是这样的：
OnClickListener：
OnClickListener loginListener = new OnClickListener()
public void onClick(View v)
/* Translation note: Original text: "Executando OnClickListener" */
Log.d(TAG, "OnClickListener has been called");
/* Translation note: Original text: "faz chamada assincrona" */
// Make an asynchronous call
new EfetuaLogin().execute();
;
所有工作都发生在EfetuaLogin AsyncTask 实现中：
class EfetuaLogin extends AsyncTask<Object, Void, String>
private final static String TAG = "LoginActivity.EfetuaLogin";
protected ProgressDialog progressDialog;
@Override
protected void onPreExecute()
super.onPreExecute();
Log.d(TAG, "Executando onPreExecute de EfetuaLogin");
//inicia diálogo de progresso, mostranto processamento com servidor.
progressDialog = ProgressDialog.show(LoginActivity.this, "Autenticando", "Contactando o servidor, por favor, aguarde alguns instantes.", true, false);
@SuppressWarnings("unchecked")
@Override
/* Translation note: Original text: "Object... parametros"
protected String doInBackground(Object... parameters)
/* Translation note: Original text: "Executando doInBackground de EfetuaLogin" */
Log.d(TAG, "Executing doInBackground of EfetuaLogin");
TextView tLogin = (TextView) findViewById(R.id.loginText);
TextView tSenha = (TextView) findViewById(R.id.senhaText);
String sLogin = tLogin.getText().toString();
String sSenha = tSenha.getText().toString();
if (sLogin.equals("") | sSenha.equals(""))
/*
Translation notes:
1) "Campos Obrigatórios" -> "Required fields"
2) "Os campos Login e Senha são obrigatórios para autenticação do Anototudo." -> "Login and Password fields are required for Anototudo authentication."
Alerta.popupAlertaComBotaoOK("Required fields", "Login and Password fields are required for Anototudo authentication.", LoginActivity.this);
progressDialog.dismiss();
return null;
else
Pattern regEx = Pattern.compile(".+@.+\\.[a-z]+");
Matcher matcher = regEx.matcher(sLogin);
if (!matcher.matches())
/*
Translation notes:
1) "Formato e-mail inválido" -> "Invalid email format"
2) "O formato do campo e-mail está inválido" -> "The email field has an invalid format"
*/
Alerta.popupAlertaComBotaoOK("Invalid email format", "The email field has an invalid format",
LoginActivity.this);
progressDialog.dismiss();
return null;
List<NameValuePair> listaParametros = new ArrayList<NameValuePair>();
listaParametros.add(new BasicNameValuePair("login", sLogin));
listaParametros.add(new BasicNameValuePair("senha", sSenha));
/* Translation note: Original text: "valores recuperados dos campos de login e senha: " */
Log.d(TAG, "values retrieved from login and password fields:" + sLogin + " | " + sSenha);
/* Translation note: Original text: "Reutiliza cliente HttpClient disponibilizado pela Aplicação." */
// Reuses `HttpClient` made available by the Application.
AnototudoApp atapp = (AnototudoApp) LoginActivity.this.getApplication();
HttpClient httpClient = atapp.getHttpClient();
String result = null;
try
result = HttpProxy.httpPost(AnototudoMetadata.URL_AUTENTICACAO, httpClient, listaParametros);
catch (IOException e)
Log.e(TAG, "IOException, Sem conectividade com o servidor do Anototudo! " + e.getMessage());
e.printStackTrace();
return result;
return result;
@Override
protected void onPostExecute(String result)
super.onPostExecute(result);
if (result == null || result.equals(""))
progressDialog.dismiss();
/*
Translation notes:
1) "Dados incorretos" -> "Incorrect data"
2) "Os dados informados não foram encontrados no Sistema! Informe novamente ou cadastre-se antes pela internet." -> "The reported data was not found in the System! Please report again or sign up on the internet first."
*/
Alerta.popupAlertaComBotaoOK(
"Incorrect data",
"The reported data was not found in the System! Please report again or sign up on the internet first.",
LoginActivity.this);
return;
/* Translation note: Original text: "Login passou persistindo info de login local no device" */
Log.d(TAG, "Login passed persisting local login info on device");
ContentValues contentValues = new ContentValues();
contentValues.put(AnototudoMetadata.LOGIN_EMAIL, sLogin);
contentValues.put(AnototudoMetadata.LOGIN_SENHA, sSenha);
contentValues.put(AnototudoMetadata.LOGIN_SENHA_GERADA, result);
LoginDB loginDB = new LoginDB();
loginDB.addLogin(LoginActivity.this, contentValues);
/* Translation note: Original text: "Persistiu info de login no device, redirecionando para menu principal do Anototudo" */
Log.d(TAG, "Persisting login info on device, redirecting to Anototudo main menu");
/* Translation note: Original text: "O retorno da chamada foi ==>> " */
Log.d(TAG, "The callback was ==>>" + result);
/* Translation note: Original text: "tudo ok chama menu principal" */
// everything ok call main menu
/* Translation note: Original text: "Device foi corretametne autenticado, chamando tela do menu principal do Anototudo." */
Log.d(TAG, "Device has been correctly authenticated by calling the main menu screen of Annotate.");
String actionName = "br.com.anototudo.intent.action.MainMenuView";
Intent intent = new Intent(actionName);
LoginActivity.this.startActivity(intent);
progressDialog.dismiss();
现在它按预期工作，但我不得不说我有点困惑，因为AsyncTask 文档说您可以使用 execute 将参数传递给您的任务。
【讨论】：
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