使用AsyncTask和Interfaces的Android程序崩溃

时间：2014-01-05 11:44:42

标签： android interface android-asynctask nullpointerexception runtime-error

我正在编写一个从数据库下载数据的程序，当我使用onPostExecute方法获取精细数据时，一切正常。因为我在调用AsynkTask类的类中需要这些数据，所以我使用方法new AsynkTaskClass.execute().get()并且它有效。最终我实现了一个接口而不是.get()方法，程序崩溃了。当我调试它时，它在方法updateJSONData()的一行中崩溃，在doInBackground中调用，而奇怪的部分是在该方法中我在实现接口时没有更改一行。我在this answer.

中实现了接口

我在这里放了一些代码：

Register.java ：我从中调用扩展AsynkTask的类的类。

package com.PacchettoPrincipale.app;

import [...]

public class Register extends Activity implements OnClickListener{

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

    private ProgressDialog pDialog;

    // Variabile utilizzata per ricevere le fermate attraverso l'interfaccia retrieveHashMapFromAsynkTask
    ArrayList<HashMap<String, String>> fermate;

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

    //testing on Emulator:
    private static final String LOGIN_URL = "http://10.0.2.2/PrimaAppAndroid/register.php";

    //ids
    private static final String TAG_SUCCESS = "success";
    private static final String TAG_MESSAGE = "message";


    //not important
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.register);

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

        mRegister = (Button)findViewById(R.id.register);
        mRegister.setOnClickListener(this);
    }


    @Override
    public void onClick(View v) {

        // HERE is where I call the AsynkTask class
        new LoadFermate(Register.this, new retrieveHashMapFromAsynkTask() {
            @Override
            public void assignment(ArrayList<HashMap<String, String>> returnedValues) {
                fermate = returnedValues;
            }
        }).execute();

        for (HashMap<String, String> fermata:fermate){
            Toast.makeText(Register.this , fermata.get("Nome"), Toast.LENGTH_SHORT).show();
        }
    }

    // is another AsynkTask class, don't look at it.
    class CreateUser extends AsyncTask<String, String, String> {[...]}

}

LoadFermate.java 是扩展AsynkTask的类，我在程序崩溃的行放置了一个大写注释。

package com.PacchettoPrincipale.app;

import [...]

public class LoadFermate extends AsyncTask<Void, Void, ArrayList<HashMap<String, String>>> {

    private Context context;
    private retrieveHashMapFromAsynkTask retrieveListener;

    public LoadFermate(Context context, retrieveHashMapFromAsynkTask retrieveListener){
        this.context = context;
        this.retrieveListener = retrieveListener;
    }

    private ProgressDialog pDialog;

    private JSONArray mComments = null;
    private ArrayList<HashMap<String, String>> mCommentList;

    //testing on Emulator:
    private static final String DOWNLOAD_FERMATE_URL = "http://10.0.2.2/PrimaAppAndroid/get/fermate.php";

    //JSON IDS:
    private static final String TAG_COD = "CodFermata";
    private static final String TAG_POSTS = "posts";
    private static final String TAG_NOME = "Nome";

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(context);
        pDialog.setMessage("Download fermate...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(true);
        pDialog.show();
    }

    @Override
    protected ArrayList<HashMap<String, String>> doInBackground(Void... voids) {
        updateJSONData();
        return mCommentList;
    }

    @Override
    protected void onPostExecute(ArrayList<HashMap<String, String>> hashMaps) {
        super.onPostExecute(hashMaps);

        pDialog.dismiss();

        if(retrieveListener != null){
            retrieveListener.assignment(hashMaps);
        }
    }

    private void updateJSONData() {

        mCommentList = new ArrayList<HashMap<String, String>>();

        JSONParser jParser = new JSONParser();

        //THE PROGRAM CRASHES AT THIS LINE
        JSONObject json = jParser.getJSONFromUrl(DOWNLOAD_FERMATE_URL);

        try {

            mComments = json.getJSONArray(TAG_POSTS);

            for (int i = 0; i < mComments.length(); i++) {
                JSONObject c = mComments.getJSONObject(i);

                int CodFermata = c.getInt(TAG_COD);
                String Nome = c.getString(TAG_NOME);

                HashMap<String, String> map = new HashMap<String, String>();

                map.put(TAG_COD, String.valueOf(CodFermata));
                map.put(TAG_NOME, Nome);

                mCommentList.add(map);
            }

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


    }
}

retrieveHashMapFromAsynkTask.java ：是界面。

package com.PacchettoPrincipale.app;

import java.util.ArrayList;
import java.util.HashMap;

public interface retrieveHashMapFromAsynkTask {
    public void assignment(ArrayList<HashMap<String, String>> returnedValues);
}

我还将LogCat过滤了Exception这个词，其中有许多NullPointerException。我认为这是关键，但我无法理解它在哪里上升。

Logcat ：

01-05 05:46:18.460        52-52/? W/dalvikvm﹕ Exception Ljava/lang/UnsatisfiedLinkError; thrown while initializing Landroid/media/videoeditor/MediaArtistNativeHelper;
01-05 05:47:31.270      382-397/system_process W/BroadcastQueue﹕ Failure sending broadcast Intent { act=android.intent.action.CONFIGURATION_CHANGED flg=0x70000010 }
    android.os.TransactionTooLargeException
            at android.os.BinderProxy.transact(Native Method)
            at android.app.ApplicationThreadProxy.scheduleRegisteredReceiver(ApplicationThreadNative.java:1059)
            at com.android.server.am.BroadcastQueue.performReceiveLocked(BroadcastQueue.java:421)
            at com.android.server.am.BroadcastQueue.deliverToRegisteredReceiverLocked(BroadcastQueue.java:507)
            at com.android.server.am.BroadcastQueue.processNextBroadcast(BroadcastQueue.java:555)
            at com.android.server.am.BroadcastQueue$1.handleMessage(BroadcastQueue.java:141)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at com.android.server.am.ActivityManagerService$AThread.run(ActivityManagerService.java:1870)
01-05 05:47:31.290      382-397/system_process W/BroadcastQueue﹕ Failure sending broadcast Intent { act=android.intent.action.CONFIGURATION_CHANGED flg=0x70000010 }
    android.os.TransactionTooLargeException
            at android.os.BinderProxy.transact(Native Method)
            at android.app.ApplicationThreadProxy.scheduleRegisteredReceiver(ApplicationThreadNative.java:1059)
            at com.android.server.am.BroadcastQueue.performReceiveLocked(BroadcastQueue.java:421)
            at com.android.server.am.BroadcastQueue.deliverToRegisteredReceiverLocked(BroadcastQueue.java:507)
            at com.android.server.am.BroadcastQueue.processNextBroadcast(BroadcastQueue.java:555)
            at com.android.server.am.BroadcastQueue$1.handleMessage(BroadcastQueue.java:141)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at com.android.server.am.ActivityManagerService$AThread.run(ActivityManagerService.java:1870)
01-05 05:47:31.310      382-397/system_process W/BroadcastQueue﹕ Failure sending broadcast Intent { act=android.intent.action.CLOSE_SYSTEM_DIALOGS flg=0x50000010 (has extras) }
    android.os.TransactionTooLargeException
            at android.os.BinderProxy.transact(Native Method)
            at android.app.ApplicationThreadProxy.scheduleRegisteredReceiver(ApplicationThreadNative.java:1059)
            at com.android.server.am.BroadcastQueue.performReceiveLocked(BroadcastQueue.java:421)
            at com.android.server.am.BroadcastQueue.deliverToRegisteredReceiverLocked(BroadcastQueue.java:507)
            at com.android.server.am.BroadcastQueue.processNextBroadcast(BroadcastQueue.java:555)
            at com.android.server.am.BroadcastQueue$1.handleMessage(BroadcastQueue.java:141)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at com.android.server.am.ActivityManagerService$AThread.run(ActivityManagerService.java:1870)
01-05 05:47:42.750      382-434/system_process E/ConnectivityService﹕ Exception trying to add a route: java.lang.IllegalStateException: command '18 interface fwmark exempt add 10.0.2.2/32' failed with '400 18 Failed to add exemption rule (File exists)'
01-05 05:47:42.870      382-434/system_process E/ConnectivityService﹕ Exception trying to add a route: java.lang.IllegalStateException: command '20 interface fwmark exempt add 10.0.2.3/32' failed with '400 20 Failed to add exemption rule (File exists)'
01-05 05:47:42.920      382-434/system_process E/ConnectivityService﹕ Exception trying to add a route: java.lang.IllegalStateException: command '21 interface route add eth0 secondary 10.0.2.2 32 0.0.0.0' failed with '400 21 ip route modification failed (No such device)'
01-05 05:47:42.960      382-434/system_process E/ConnectivityService﹕ Exception trying to add a route: java.lang.IllegalStateException: command '22 interface route add eth0 secondary 0.0.0.0 0 10.0.2.2' failed with '400 22 ip route modification failed (No such device)'
01-05 05:47:52.480      382-659/system_process E/ConnectivityService﹕ Exception trying to add a route: java.lang.IllegalStateException: command '30 interface fwmark exempt add 10.0.2.2/32' failed with '400 30 Failed to add exemption rule (File exists)'
01-05 05:47:52.720      382-659/system_process E/ConnectivityService﹕ Exception trying to add a route: java.lang.IllegalStateException: command '32 interface fwmark exempt add 173.194.40.6/32' failed with '400 32 Failed to add exemption rule (File exists)'
01-05 05:47:55.950      382-659/system_process E/ConnectivityService﹕ Exception trying to add a route: java.lang.IllegalStateException: command '34 interface fwmark exempt add 10.0.2.2/32' failed with '400 34 Failed to add exemption rule (File exists)'
01-05 05:47:56.080      382-659/system_process E/ConnectivityService﹕ Exception trying to add a route: java.lang.IllegalStateException: command '36 interface fwmark exempt add 173.194.40.0/32' failed with '400 36 Failed to add exemption rule (File exists)'
01-05 05:47:57.240      663-678/com.android.systemui W/Binder﹕ Binder call failed.
    android.os.DeadObjectException
            at android.os.BinderProxy.transact(Native Method)
            at android.content.IIntentReceiver$Stub$Proxy.performReceive(IIntentReceiver.java:124)
            at android.app.ActivityThread$ApplicationThread.scheduleRegisteredReceiver(ActivityThread.java:816)
            at android.app.ApplicationThreadNative.onTransact(ApplicationThreadNative.java:394)
            at android.os.Binder.execTransact(Binder.java:404)
            at dalvik.system.NativeStart.run(Native Method)
01-05 05:47:57.270      663-678/com.android.systemui E/JavaBinder﹕ *** Uncaught remote exception!  (Exceptions are not yet supported across processes.)
    java.lang.RuntimeException: android.os.DeadObjectException
            at android.os.Parcel.writeException(Parcel.java:1366)
            at android.os.Binder.execTransact(Binder.java:410)
            at dalvik.system.NativeStart.run(Native Method)
     Caused by: android.os.DeadObjectException
            at android.os.BinderProxy.transact(Native Method)
            at android.content.IIntentReceiver$Stub$Proxy.performReceive(IIntentReceiver.java:124)
            at android.app.ActivityThread$ApplicationThread.scheduleRegisteredReceiver(ActivityThread.java:816)
            at android.app.ApplicationThreadNative.onTransact(ApplicationThreadNative.java:394)
            at android.os.Binder.execTransact(Binder.java:404)
            at dalvik.system.NativeStart.run(Native Method)
01-05 05:47:59.220      382-659/system_process E/ConnectivityService﹕ Exception trying to add a route: java.lang.IllegalStateException: command '38 interface fwmark exempt add 10.0.2.2/32' failed with '400 38 Failed to add exemption rule (File exists)'
01-05 05:47:59.320      382-659/system_process E/ConnectivityService﹕ Exception trying to add a route: java.lang.IllegalStateException: command '40 interface fwmark exempt add 173.194.40.5/32' failed with '400 40 Failed to add exemption rule (File exists)'
01-05 05:48:02.400      382-659/system_process E/ConnectivityService﹕ Exception trying to add a route: java.lang.IllegalStateException: command '42 interface fwmark exempt add 10.0.2.2/32' failed with '400 42 Failed to add exemption rule (File exists)'
01-05 05:48:02.480      382-659/system_process E/ConnectivityService﹕ Exception trying to add a route: java.lang.IllegalStateException: command '44 interface fwmark exempt add 173.194.40.7/32' failed with '400 44 Failed to add exemption rule (File exists)'
01-05 05:57:13.340    1104-1104/? W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0xb3a5cba8)
01-05 05:57:22.380    1104-1104/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.PacchettoPrincipale.app, PID: 1104
    java.lang.NullPointerException
            at com.PacchettoPrincipale.app.Register.onClick(Register.java:87)
            at android.view.View.performClick(View.java:4438)
            at android.view.View$PerformClick.run(View.java:18422)
            at android.os.Handler.handleCallback(Handler.java:733)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5017)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
            at dalvik.system.NativeStart.main(Native Method)
01-05 05:58:03.480      382-571/system_process W/InputMethodManagerService﹕ Got RemoteException sending setActive(false) notification to pid 1104 uid 10052
01-05 05:58:03.500      530-546/com.android.inputmethod.latin W/Binder﹕ Caught a RuntimeException from the binder stub implementation.
    java.lang.NullPointerException
            at android.inputmethodservice.IInputMethodWrapper.setSessionEnabled(IInputMethodWrapper.java:280)
            at com.android.internal.view.IInputMethod$Stub.onTransact(IInputMethod.java:129)
            at android.os.Binder.execTransact(Binder.java:404)
            at dalvik.system.NativeStart.run(Native Method)
01-05 05:58:16.800      382-575/system_process W/InputMethodManagerService﹕ Got RemoteException sending setActive(false) notification to pid 1136 uid 10052
01-05 05:58:16.890      530-543/com.android.inputmethod.latin W/Binder﹕ Caught a RuntimeException from the binder stub implementation.
    java.lang.NullPointerException
            at android.inputmethodservice.IInputMethodWrapper.setSessionEnabled(IInputMethodWrapper.java:280)
            at com.android.internal.view.IInputMethod$Stub.onTransact(IInputMethod.java:129)
            at android.os.Binder.execTransact(Binder.java:404)
            at dalvik.system.NativeStart.run(Native Method)

另一个奇怪的部分是nullPointer位于寄存器第87行，这是我没有通过调试到达的行。它在到达之前崩溃：它在doInBackground期间崩溃，而注册：87在onPostExecute之后执行。

提前感谢您的回答！

1 个答案:

答案 0 :(得分：2)

这是NullPointerException ... 

   for (HashMap<String, String> fermata : fermate){
        Toast.makeText(Register.this , fermata.get("Nome"), Toast.LENGTH_SHORT).show();
   }

此处fermate为空。您正在fermate回调中初始化retrieveHashMapFromAsynkTask，AsyncTask将调用onPostExecute()。AsyncTask。您应该等待retrieveHashMapFromAsynkTask完成任务或将Toast移至 new LoadFermate(Register.this, new retrieveHashMapFromAsynkTask() { @Override public void assignment(ArrayList<HashMap<String, String>> returnedValues) { fermate = returnedValues; for (HashMap<String, String> fermata:fermate){ Toast.makeText(Register.this , fermata.get("Nome"), Toast.LENGTH_SHORT).show(); } } }).execute(); 实施...... 

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