android - 如何在 Android 中进行后台工作时使用 AsyncTask 显示 ProgressDialog？

Question

Possible Duplicate:
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 Activity 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，该方法实际上向服务器执行 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);
    }
};

Answer 1

将你的 ProgressDialog 放在 onPreExecute 中，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);