Android Error while filling Array inside AsyncTask

Question

I want to fill an array so i can append that results to a TextView, but the app keep crashing:

04-02 23:45:29.286: E/AndroidRuntime(6620): FATAL EXCEPTION: AsyncTask #3
04-02 23:45:29.286: E/AndroidRuntime(6620): java.lang.RuntimeException: An error occured while executing doInBackground()
04-02 23:45:29.286: E/AndroidRuntime(6620):     at android.os.AsyncTask$3.done(AsyncTask.java:200)
04-02 23:45:29.286: E/AndroidRuntime(6620):     at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:274)
04-02 23:45:29.286: E/AndroidRuntime(6620):     at java.util.concurrent.FutureTask.setException(FutureTask.java:125)
04-02 23:45:29.286: E/AndroidRuntime(6620):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:308)
04-02 23:45:29.286: E/AndroidRuntime(6620):     at java.util.concurrent.FutureTask.run(FutureTask.java:138)
04-02 23:45:29.286: E/AndroidRuntime(6620):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1088)
04-02 23:45:29.286: E/AndroidRuntime(6620):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:581)
04-02 23:45:29.286: E/AndroidRuntime(6620):     at java.lang.Thread.run(Thread.java:1019)
04-02 23:45:29.286: E/AndroidRuntime(6620): Caused by: java.lang.NullPointerException
04-02 23:45:29.286: E/AndroidRuntime(6620):     at com.gettford.community.MessageActivity$Mensajes.doInBackground(MessageActivity.java:166)
04-02 23:45:29.286: E/AndroidRuntime(6620):     at com.gettford.community.MessageActivity$Mensajes.doInBackground(MessageActivity.java:1)
04-02 23:45:29.286: E/AndroidRuntime(6620):     at android.os.AsyncTask$2.call(AsyncTask.java:185)
04-02 23:45:29.286: E/AndroidRuntime(6620):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:306)
04-02 23:45:29.286: E/AndroidRuntime(6620):     ... 4 more

I have two strings:

public String[] mensa;
public String[] NomUsuario;

then i do the AsynTask, in the doInBackround:

// Retrieve JSON Objects from the given URL address
            jsonobject = JSONfunctions
                    .getJSONfromURL("http://www.gettford.net/comunidad/api/chat_conv.php?user="+usuarioID+"&id="+idsala);

            try {
                // Locate the array name in JSON

                jsonarray = jsonobject.getJSONArray("lista");

                for (int i = 0; i < jsonarray.length(); i++) {
                    //HashMap<String, String> map = new HashMap<String, String>();
                    jsonobject  = jsonarray.getJSONObject(i);

                    // Retrive JSON Objects
                    //usuario = jsonobject.getString("Nombre");
                    mensa[i] = jsonobject.getString("mensaje");
                    NomUsuario[i] = jsonobject.getString("NomUsuario");
                    Log.i("mensaje",mensa[i]);

                }
            } catch (JSONException e) {
                Log.e("Error", e.getMessage());
                e.printStackTrace();
            }
            return null;
        }

        @Override
        protected void onPostExecute(Void args) {
            lblMessage.setText("");
            for (int i= 0; i < mensa.length; i++){
            lblMessage.append(NomUsuario[i]+": "+mensa[i] + "\n");
            }
        }

The line giving the error is this one:

mensa[i] = jsonobject.getString("mensaje");

Appreciate the help

Thanks!

You have not initialized mensa only declared it public String[] mensa; — Raghunandan
– Raghunandan, Commented Apr 3, 2014 at 4:26

Lucifer · Accepted Answer · 2014-04-03 04:28:10Z

6

You just forgot to initialize your Array variables. On starting of the try block you need to initialize your Array variable like below,

try {
            // Locate the array name in JSON 
           mensa = new String[jsonarray.length()]; // Add this line.
           NomUsuario = new String[jsonarray.length()]; // Add this line.

answered Apr 3, 2014 at 4:28

Lucifer

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Comments

Lazy Ninja · Accepted Answer · 2014-04-03 04:25:59Z

4

You should add mensa = new String[jsonarray.length()] before the for loop.

answered Apr 3, 2014 at 4:25

Lazy Ninja

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5 Comments

Douglas Roos Over a year ago

Thanks, exactly how? I though that it was being initialized by the mensa[i] = jsonobject.getString("mensaje");

Raghunandan Over a year ago

@DouglasRoos look at the docs docs.oracle.com/javase/tutorial/java/nutsandbolts/arrays.html and its better to use a list

Lazy Ninja Over a year ago

@DouglasRoos , in that line you are adding values to an array which is not initialized, reason you got a null pointer.

Lazy Ninja Over a year ago

And you should initiliaze NomUsuario as well.@DouglasRoos

Douglas Roos Over a year ago

Thanks, yup, now is working, great, thank you very much for the help. I didn't knew how to look for it on google. Almost 2 hours fighting with it

SilentKiller · Accepted Answer · 2014-04-03 04:26:31Z

4

You have not initialize any of your array.

jsonarray = jsonobject.getJSONArray("lista");

if (jsonarray.length() > 0) {
// Initialized both array if the size of that JSONArray is grater then 0
mensa = new String[jsonarray.length()]
NomUsuario= new String[jsonarray.length()]

    for (int i = 0; i < jsonarray.length(); i++) {
        jsonobject  = jsonarray.getJSONObject(i);
        mensa[i] = jsonobject.getString("mensaje");
        NomUsuario[i] = jsonobject.getString("NomUsuario");
        Log.i("mensaje",mensa[i]);
    }
}

answered Apr 3, 2014 at 4:26

SilentKiller

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Comments

Hariharan · Accepted Answer · 2014-04-03 04:26:04Z

3

Try this..

Put mensa and NomUsuario initialize String array size before the for loop

mensa = new String[jsonarray.length()];
NomUsuario = new String[jsonarray.length()];
for (int i = 0; i < jsonarray.length(); i++) {

answered Apr 3, 2014 at 4:26

Hariharan

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