asyncTask＃1出错

Question

我在asynctask中遇到麻烦。有致命的错误。这是发生错误的部分。它告诉我String成功未使用。整个代码现已发布。请帮助我在asynctask中遇到麻烦。有致命的错误。这是发生错误的部分。它告诉我String成功未使用。整个代码现已发布。请帮助我在asynctask中遇到麻烦。有致命的错误。这是发生错误的部分。它告诉我String成功未使用。整个代码现已发布。请帮助我在asynctask中遇到麻烦。有致命的错误。这是发生错误的部分。它告诉我String成功未使用。整个代码现已发布。请帮忙

package com.example.ram2;

import java.util.ArrayList;
import java.util.List;

import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONException;
import org.json.JSONObject;

import android.app.Activity;
import android.app.ProgressDialog;

import android.os.AsyncTask;
import android.os.Bundle;

import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class Login extends Activity implements OnClickListener {

    EditText user, pass;
    Button mSubmit, mRegister;

    ProgressDialog pDialog;

    JSONParser jsonParser = new JSONParser();

    private static final String LOGIN_URL = "http://10.0.2.2/FuckAnd/login.php";

    static final String TAG_SUCCESS = "success";
    static final String TAG_MESSAGE = "message";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.login);

        user = (EditText) findViewById(R.id.username);
        pass = (EditText) findViewById(R.id.password);

        mSubmit = (Button) findViewById(R.id.login);
        mSubmit.setOnClickListener(this);

    }

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
            new AttemptLogin().execute();

    }

    public class AttemptLogin extends AsyncTask<String, String, String> {

        @Override
        protected void onPreExecute() {

            super.onPreExecute();
            pDialog = new ProgressDialog(Login.this);
            pDialog.setMessage("Logging in...");
            pDialog.setIndeterminate(false);
            pDialog.setCancelable(true);
            pDialog.show();
            pDialog.dismiss();
            finish() ;
        }

        @Override
        protected String doInBackground(String... args) {
            // TODO Auto-generated method stub
            String username = user.getText().toString();
            String password = pass.getText().toString();
            String success = null;

                try {

                List<NameValuePair> params = new ArrayList<NameValuePair>();
                params.add(new BasicNameValuePair("username", username));               
                params.add(new BasicNameValuePair("password", password));

                Log.d("request!", "starting");

                JSONObject json = jsonParser.makeHttpRequest(LOGIN_URL, "POST",
                        params);

                Log.d("Login attempt", json.toString());

                success= json.getString("success");

                   } catch (JSONException e) {
                        e.printStackTrace();
                    }

                    return null;
        }

        protected void onPostExecute(String result) {
            super.onPostExecute(result);
            //JSONObject json;
            // dismiss the dialog once product deleted
            pDialog.dismiss();
            //if (TAG_SUCCESS == null) {

            if (result.equals("success")) {
            //if (success.equals(success)) {
                //Log.d("Login Successful!", json.toString());
                Toast.makeText(Login.this, "Login Successful!", Toast.LENGTH_SHORT).show();
                //Toast.makeText(LoginActivity.this, "Login Successful!", Toast.LENGTH_LONG).show();
                //Intent i = new Intent(LoginActivity.this, PortalContents.class);
                finish();
                //startActivity(i);
                //return null;

}
              else {
                //Log.d("Login Failure!", json.getString(TAG_MESSAGE));
                Toast.makeText(Login.this, "Login Fail!", Toast.LENGTH_LONG).show();
                //return json.getString(TAG_MESSAGE);
                //return json.getString(TAG_MESSAGE);

            }

        }

}

}

Answer 1

您需要从doInBackground返回onPostExecute所期望的类型字符串。从doInBackground返回也需要匹配AsyncTask声明中的第三个参数，它是onPostExecute的预期类型（AsyncTask上的每个参数需要分别匹配onPreExecute，doInBackground和onPostExecute;请注意前两个是数据类型的数组。）

因此return null会导致onPostExecute(String result)的问题。

有关AsyncTasks的更多信息，请参阅http://developer.android.com/reference/android/os/AsyncTask.html的开发者指南。

Answer 2

试试这个：

protected String doInBackground(String... args) {
      // TODO Auto-generated method stub
      String username = arg[0];
      String password = arg[1];
      String success = null; //this keeps getting error
//...
}

和

new Task().execute(user.getText().toString(),pass.getText().toString());