致命的异常：asynctask＃1 java.lang.runtimeException：在排除doinbackground时发生错误

Question

当我登录按钮时，我的登录和注册类中出现同样的问题，我得到一些LogCat错误。可有人请向我解释的错误，以及如何摆脱它

我登录类

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logcat的

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(); 
    } 

使用这样的..获取用户名和密码上onPreExecute（）本身

Answer 2

我看到两个主要问题在你的实现中。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(); 
      } 
} 

，你在doInBackground调用startActivity后，它被称为。由于您当前的活动正在完成

pDialog.dismiss(); 

将导致WindowLeaked异常。第二

Toast.makeText(LoginScreen.this, 

上下文中可能不再有效，导致NPE

Answer 3

您无法启动从doInBackground becz已经不多了UI线程的活动所以总是试图从onPreExecute做UI动作：

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(); 
} 

如何调用login：

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