致命異常：asynctask＃1 java.lang.runtimeException：執行doinbackground時發生錯誤

Question

我每當我按下登錄按鈕時，都會在登錄和注冊類中遇到相同的問題，但出現一些LogCat錯誤。 有人可以給我解釋一下錯誤以及如何消除它

我的登入課程

package com.Flawed.hearmeout;

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

import library.JSONParser;

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.content.Intent;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.os.AsyncTask;
import android.os.Bundle;
import android.preference.PreferenceManager;
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 LoginScreen extends Activity implements OnClickListener{

    private EditText user, pass;
    private Button mSubmit, mRegister;

     // Progress Dialog
    private ProgressDialog pDialog;

    // JSON parser class
    JSONParser jsonParser = new JSONParser();

    //php login script location:

    //localhost :
    //testing on your device
    //put your local ip instead,  on windows, run CMD > ipconfig
    //or in mac's terminal type ifconfig and look for the ip under en0 or en1
   // private static final String LOGIN_URL = "http://xxx.xxx.x.x:1234/webservice/login.php";

    //testing on Emulator:
    private static final String LOGIN_URL = "http://10.0.2.2:1234/webservice/login.php";

  //testing from a real server:
    //private static final String LOGIN_URL = "http://www.yourdomain.com/webservice/login.php";

    //JSON element ids from repsonse of php script:
    private static final String TAG_SUCCESS = "success";
    private static final String TAG_MESSAGE = "message";

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

        //setup input fields
        user = (EditText)findViewById(R.id.username);
        pass = (EditText)findViewById(R.id.password);

        //setup buttons
        mSubmit = (Button)findViewById(R.id.login);
        mRegister = (Button)findViewById(R.id.register);

        //register listeners
        mSubmit.setOnClickListener(this);
        mRegister.setOnClickListener(this);

    }

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        switch (v.getId()) {
        case R.id.login:
                new AttemptLogin().execute();
            break;
        case R.id.register:
                Intent i = new Intent(this, SignUp.class);
                startActivity(i);
            break;

        default:
            break;
        }
    }

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

         /**
         * Before starting background thread Show Progress Dialog
         * */
        boolean failure = false;

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            pDialog = new ProgressDialog(LoginScreen.this);
            pDialog.setMessage("Attempting login...");
            pDialog.setIndeterminate(false);
            pDialog.setCancelable(true);
            pDialog.show();
        }

        @Override
        protected String doInBackground(String... args) {
            // TODO Auto-generated method stub
             // Check for success tag
            int success;
            String username = user.getText().toString();
            String password = pass.getText().toString();
            try {
                // Building Parameters
                List<NameValuePair> params = new ArrayList<NameValuePair>();
                params.add(new BasicNameValuePair("username", username));
                params.add(new BasicNameValuePair("password", password));

                Log.d("request!", "starting");
                // getting product details by making HTTP request
                JSONObject json = jsonParser.makeHttpRequest(
                       LOGIN_URL, "POST", params);

                // check your log for json response
                Log.d("Login attempt", json.toString());

                // json success tag
              //upon successful login, save username:
                // Async json success tag
                success = json.getInt(TAG_SUCCESS);
                if (success == 1) {
                    Log.d("Login Successful!", json.toString());
                    // save user data
                    SharedPreferences sp = PreferenceManager
                            .getDefaultSharedPreferences(LoginScreen.this);
                    Editor edit = sp.edit();
                    edit.putString("username", username);
                    edit.commit();

                    Intent i = new Intent(LoginScreen.this, ReadComments.class);
                    finish();
                    startActivity(i);
                    return json.getString(TAG_MESSAGE);
                } else {
                    Log.d("Login Failure!", json.getString(TAG_MESSAGE));
                    return json.getString(TAG_MESSAGE);
                }

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

            return null;

        }
        /**
         * After completing background task Dismiss the progress dialog
         * **/
        protected void onPostExecute(String file_url) {
            // dismiss the dialog once product deleted
            pDialog.dismiss();
            if (file_url != null){
                Toast.makeText(LoginScreen.this, file_url, Toast.LENGTH_LONG).show();
            }

        }
       }   
    }

我的LogCat

12-04 21:18:31.051: D/dalvikvm(1598): GC_FOR_ALLOC freed 267K, 10% free 9406K/10448K, paused 11ms, total 13ms
12-04 21:18:31.061: D/dalvikvm(1598): GC_FOR_ALLOC freed 95K, 11% free 9409K/10548K, paused 10ms, total 10ms
12-04 21:18:31.066: I/dalvikvm-heap(1598): Grow heap (frag case) to 11.018MB for 1127536-byte allocation
12-04 21:18:31.076: D/dalvikvm(1598): GC_FOR_ALLOC freed 1K, 10% free 10509K/11652K, paused 10ms, total 10ms
12-04 21:18:31.096: D/request!(1598): starting
12-04 21:18:31.096: W/dalvikvm(1598): threadid=12: thread exiting with uncaught exception (group=0x41fa7c08)
12-04 21:18:31.096: E/AndroidRuntime(1598): FATAL EXCEPTION: AsyncTask #1
12-04 21:18:31.096: E/AndroidRuntime(1598): Process: com.Flawed.hearmeout, PID: 1598
12-04 21:18:31.096: E/AndroidRuntime(1598): java.lang.RuntimeException: An error occured while executing doInBackground()
12-04 21:18:31.096: E/AndroidRuntime(1598):     at android.os.AsyncTask$3.done(AsyncTask.java:300)
12-04 21:18:31.096: E/AndroidRuntime(1598):     at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
12-04 21:18:31.096: E/AndroidRuntime(1598):     at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
12-04 21:18:31.096: E/AndroidRuntime(1598):     at java.util.concurrent.FutureTask.run(FutureTask.java:242)
12-04 21:18:31.096: E/AndroidRuntime(1598):     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
12-04 21:18:31.096: E/AndroidRuntime(1598):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
12-04 21:18:31.096: E/AndroidRuntime(1598):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
12-04 21:18:31.096: E/AndroidRuntime(1598):     at java.lang.Thread.run(Thread.java:841)
12-04 21:18:31.096: E/AndroidRuntime(1598): Caused by: java.lang.NullPointerException
12-04 21:18:31.096: E/AndroidRuntime(1598):     at com.Flawed.hearmeout.SignUp$CreateUser.doInBackground(SignUp.java:112)
12-04 21:18:31.096: E/AndroidRuntime(1598):     at com.Flawed.hearmeout.SignUp$CreateUser.doInBackground(SignUp.java:1)
12-04 21:18:31.096: E/AndroidRuntime(1598):     at android.os.AsyncTask$2.call(AsyncTask.java:288)
12-04 21:18:31.096: E/AndroidRuntime(1598):     at java.util.concurrent.FutureTask.run(FutureTask.java:237)
12-04 21:18:31.096: E/AndroidRuntime(1598):     ... 4 more
12-04 21:18:31.141: D/ProgressBar(1598): updateDrawableBounds: left = 0
12-04 21:18:31.141: D/ProgressBar(1598): updateDrawableBounds: top = 0
12-04 21:18:31.141: D/ProgressBar(1598): updateDrawableBounds: right = 96
12-04 21:18:31.141: D/ProgressBar(1598): updateDrawableBounds: bottom = 96
12-04 21:18:31.746: E/WindowManager(1598): android.view.WindowLeaked: Activity com.Flawed.hearmeout.SignUp has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView{429c0ab8 V.E..... R......D 0,0-684,192} that was originally added here
12-04 21:18:31.746: E/WindowManager(1598):  at android.view.ViewRootImpl.<init>(ViewRootImpl.java:467)
12-04 21:18:31.746: E/WindowManager(1598):  at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:267)
12-04 21:18:31.746: E/WindowManager(1598):  at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:69)
12-04 21:18:31.746: E/WindowManager(1598):  at android.app.Dialog.show(Dialog.java:289)
12-04 21:18:31.746: E/WindowManager(1598):  at com.Flawed.hearmeout.SignUp$CreateUser.onPreExecute(SignUp.java:89)
12-04 21:18:31.746: E/WindowManager(1598):  at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:587)
12-04 21:18:31.746: E/WindowManager(1598):  at android.os.AsyncTask.execute(AsyncTask.java:535)
12-04 21:18:31.746: E/WindowManager(1598):  at com.Flawed.hearmeout.SignUp.onClick(SignUp.java:71)
12-04 21:18:31.746: E/WindowManager(1598):  at android.view.View.performClick(View.java:4654)
12-04 21:18:31.746: E/WindowManager(1598):  at android.view.View$PerformClick.run(View.java:19438)
12-04 21:18:31.746: E/WindowManager(1598):  at android.os.Handler.handleCallback(Handler.java:733)
12-04 21:18:31.746: E/WindowManager(1598):  at android.os.Handler.dispatchMessage(Handler.java:95)
12-04 21:18:31.746: E/WindowManager(1598):  at android.os.Looper.loop(Looper.java:146)
12-04 21:18:31.746: E/WindowManager(1598):  at android.app.ActivityThread.main(ActivityThread.java:5602)
12-04 21:18:31.746: E/WindowManager(1598):  at java.lang.reflect.Method.invokeNative(Native Method)
12-04 21:18:31.746: E/WindowManager(1598):  at java.lang.reflect.Method.invoke(Method.java:515)
12-04 21:18:31.746: E/WindowManager(1598):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
12-04 21:18:31.746: E/WindowManager(1598):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
12-04 21:18:31.746: E/WindowManager(1598):  at dalvik.system.NativeStart.main(Native Method)
12-04 21:23:31.116: I/Process(1598): Sending signal. PID: 1598 SIG: 9
12-04 21:23:52.541: D/dalvikvm(2571): GC_FOR_ALLOC freed 71K, 9% free 9379K/10228K, paused 10ms, total 11ms
12-04 21:23:52.541: I/dalvikvm-heap(2571): Grow heap (frag case) to 10.989MB for 1127536-byte allocation
12-04 21:23:52.556: D/dalvikvm(2571): GC_FOR_ALLOC freed 1K, 8% free 10479K/11332K, paused 16ms, total 16ms
12-04 21:23:52.571: D/request!(2571): starting
12-04 21:23:52.576: W/dalvikvm(2571): threadid=11: thread exiting with uncaught exception (group=0x41fa7c08)
12-04 21:23:52.576: E/AndroidRuntime(2571): FATAL EXCEPTION: AsyncTask #1
12-04 21:23:52.576: E/AndroidRuntime(2571): Process: com.Flawed.hearmeout, PID: 2571
12-04 21:23:52.576: E/AndroidRuntime(2571): java.lang.RuntimeException: An error occured while executing doInBackground()
12-04 21:23:52.576: E/AndroidRuntime(2571):     at android.os.AsyncTask$3.done(AsyncTask.java:300)
12-04 21:23:52.576: E/AndroidRuntime(2571):     at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
12-04 21:23:52.576: E/AndroidRuntime(2571):     at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
12-04 21:23:52.576: E/AndroidRuntime(2571):     at java.util.concurrent.FutureTask.run(FutureTask.java:242)
12-04 21:23:52.576: E/AndroidRuntime(2571):     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
12-04 21:23:52.576: E/AndroidRuntime(2571):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
12-04 21:23:52.576: E/AndroidRuntime(2571):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
12-04 21:23:52.576: E/AndroidRuntime(2571):     at java.lang.Thread.run(Thread.java:841)
12-04 21:23:52.576: E/AndroidRuntime(2571): Caused by: java.lang.NullPointerException
12-04 21:23:52.576: E/AndroidRuntime(2571):     at com.Flawed.hearmeout.LoginScreen$AttemptLogin.doInBackground(LoginScreen.java:130)
12-04 21:23:52.576: E/AndroidRuntime(2571):     at com.Flawed.hearmeout.LoginScreen$AttemptLogin.doInBackground(LoginScreen.java:1)
12-04 21:23:52.576: E/AndroidRuntime(2571):     at android.os.AsyncTask$2.call(AsyncTask.java:288)
12-04 21:23:52.576: E/AndroidRuntime(2571):     at java.util.concurrent.FutureTask.run(FutureTask.java:237)
12-04 21:23:52.576: E/AndroidRuntime(2571):     ... 4 more
12-04 21:23:52.606: D/ProgressBar(2571): updateDrawableBounds: left = 0
12-04 21:23:52.606: D/ProgressBar(2571): updateDrawableBounds: top = 0
12-04 21:23:52.606: D/ProgressBar(2571): updateDrawableBounds: right = 96
12-04 21:23:52.606: D/ProgressBar(2571): updateDrawableBounds: bottom = 96
12-04 21:23:52.981: E/WindowManager(2571): android.view.WindowLeaked: Activity com.Flawed.hearmeout.LoginScreen has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView{42897a78 V.E..... R....... 0,0-684,192} that was originally added here
12-04 21:23:52.981: E/WindowManager(2571):  at android.view.ViewRootImpl.<init>(ViewRootImpl.java:467)
12-04 21:23:52.981: E/WindowManager(2571):  at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:267)
12-04 21:23:52.981: E/WindowManager(2571):  at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:69)
12-04 21:23:52.981: E/WindowManager(2571):  at android.app.Dialog.show(Dialog.java:289)
12-04 21:23:52.981: E/WindowManager(2571):  at com.Flawed.hearmeout.LoginScreen$AttemptLogin.onPreExecute(LoginScreen.java:108)
12-04 21:23:52.981: E/WindowManager(2571):  at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:587)
12-04 21:23:52.981: E/WindowManager(2571):  at android.os.AsyncTask.execute(AsyncTask.java:535)
12-04 21:23:52.981: E/WindowManager(2571):  at com.Flawed.hearmeout.LoginScreen.onClick(LoginScreen.java:82)
12-04 21:23:52.981: E/WindowManager(2571):  at android.view.View.performClick(View.java:4654)
12-04 21:23:52.981: E/WindowManager(2571):  at android.view.View$PerformClick.run(View.java:19438)
12-04 21:23:52.981: E/WindowManager(2571):  at android.os.Handler.handleCallback(Handler.java:733)
12-04 21:23:52.981: E/WindowManager(2571):  at android.os.Handler.dispatchMessage(Handler.java:95)
12-04 21:23:52.981: E/WindowManager(2571):  at android.os.Looper.loop(Looper.java:146)
12-04 21:23:52.981: E/WindowManager(2571):  at android.app.ActivityThread.main(ActivityThread.java:5602)
12-04 21:23:52.981: E/WindowManager(2571):  at java.lang.reflect.Method.invokeNative(Native Method)
12-04 21:23:52.981: E/WindowManager(2571):  at java.lang.reflect.Method.invoke(Method.java:515)
12-04 21:23:52.981: E/WindowManager(2571):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
12-04 21:23:52.981: E/WindowManager(2571):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
12-04 21:23:52.981: E/WindowManager(2571):  at dalvik.system.NativeStart.main(Native Method)
12-04 21:23:54.551: I/Process(2571): Sending signal. PID: 2571 SIG: 9

Answer 1

 @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(LoginScreen.this);
        pDialog.setMessage("Attempting login...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(true);
        pDialog.show();
        String username = user.getText().toString();
        String password = pass.getText().toString();
    }

這樣使用。.在onPreExecute（）本身上獲取用戶名和密碼

Answer 2

我在您的實施過程中看到兩個主要問題 。 在onPostExecute你有

protected void onPostExecute(String file_url) {
            // dismiss the dialog once product deleted
            pDialog.dismiss();
            if (file_url != null){
                Toast.makeText(LoginScreen.this, file_url, Toast.LENGTH_LONG).show();
            }
}

它在doInBackground調用startActivity之后被調用。 由於您當前的活動即將結束

   pDialog.dismiss();

將導致WindowLeaked異常。 第二

  Toast.makeText(LoginScreen.this,

上下文可能不再有效，導致NPE

Answer 3

您無法從doInBackground開始活動，因為becz快用完了UI線程，因此請始終嘗試從onPreExecute進行UI操作：

public void login(final Context context,final String username,final String password){

   new AsyncTask<Void,Void,JSONObject>(){
   @Override
   protected void onPreExecute() {
      super.onPreExecute();
      pDialog = new ProgressDialog(context);
      pDialog.setMessage("Attempting login...");
      pDialog.setIndeterminate(false);
      pDialog.setCancelable(true);
      pDialog.show();
   }

   @Override
   protected JSONObject doInBackground(Void... params) {

      List<NameValuePair> params = new ArrayList<NameValuePair>();
      params.add(new BasicNameValuePair("username", username));
      params.add(new BasicNameValuePair("password", password));
      return  jsonParser.makeHttpRequest(LOGIN_URL, "POST", params);
   }

   @Override
   protected void onPostExecute(JSONObject response) {
      super.onPostExecute(response);
      if(pDialog!=null){
         pDialog.dismiss();
      }
      if(response!=null){
         try {
              int success = response.getInt(TAG_SUCCESS);
              if (success == 1) {
                  Log.d("Login Successful!", response.toString());
                  // save user data
                  SharedPreferences sp = context.getSharedPreferences(context.getString(R.string.app_name), MODE_PRIVATE);
                  Editor edit = sp.edit();
                  edit.putString("username", username);
                  edit.commit();

                  Intent i = new Intent(context, ReadComments.class);
                  context.startActivity(i);
                  ((Activity)context).finish();
               }else{
                   Toast.makeText(context, response.getString(TAG_MESSAGE), Toast.LENGTH_LONG).show();
               }
          }catch (JSONException e){
             e.printStackTrace();
          }
       }
   }
 }.execute();
}

如何呼叫登入：

case R.id.login:
     login(this,user.getText().toString(),pass.getText().toString());
     break;