NullPointerException when using Aysnctask in android

Question

I am writing an android application, I use Aysnctask to get the current weather using openWeatherAPI. but it gives me a NullPointerException at this line :

results[0]=t;

this is the Aysnctask class I wrote:

private class GetWeather extends AsyncTask<String[], Void, String[]>{

    @Override
protected String[] doInBackground(String... params) {
    // TODO Auto-generated method stub
    try {
        params[0]=currentLatitude;
        params[1]=currentLongitude;
        String Url1="http://api.openweathermap.org/data/2.5/weather?lat="+currentLatitude+"&lon="+currentLongitude;
        s1=getJson(Url1);
        //Toast.makeText(getApplicationContext(), "the ss = "+s1, Toast.LENGTH_LONG).show();
        Log.d("yes","yes");

        if(s1!=null){

                JSONObject jObj1 = new JSONObject(s1);
                Log.d("jsonOOO","jsonOOO");

                Tem=  jObj1.getJSONObject("main").getDouble("temp");
                Log.d("temmm","temmm="+String.valueOf(Tem));
                pressure=jObj1.getJSONObject("main").getDouble("pressure");
                humm=jObj1.getJSONObject("main").getDouble("humidity");
                wind=jObj1.getJSONObject("wind").getDouble("speed");
                desc=jObj1.getJSONObject("weather").getDouble("description");

                double tem_c=Tem-273.15;
                Log.d("tem11","tem11="+String.valueOf(tem_c));
                String t=Double.toString(tem_c);
                String t=String.valueOf(tem_c);

                Log.d("tem22","tem22="+t);
                results[0]=t;
                Log.d("results[0]=","results[0]"+results[0]);
                results[1]=String.valueOf(pressure);
                results[2]=String.valueOf(humm);
                results[3]=String.valueOf(wind);
                results[4]=String.valueOf(desc);

         }

    } catch (Exception e) {
        // TODO: handle exception
    }
    return results;
}//do in background


@Override
protected void onPostExecute(String[] results) {
    temp.setText(results[0]+"°C");
    hum.setText(results[1]+ "%");
    press.setText(results[2]+ " hPa");
    windSpeed.setText(results[3]+ " mps");
    condDescr.setText(results[4]);

}

}

the value of temp,pressure, etc.. is not null. I tried to print them in logCat and they were printed.

probably forget to initialize `results` Array before adding elements? — ρяσѕρєя K, Dec 04 '13 at 08:21
How you are able to declare String t twice. `String t= Double.toString(tem_c); String t=String.valueOf(tem_c);` — Pradip, Dec 04 '13 at 08:29
I dont know how you are using these two lines String t=Double.toString(tem_c); String t=String.valueOf(tem_c); how two string variables with same t exists?? — Smogger, Dec 04 '13 at 08:31

score 1 · Accepted Answer · answered Dec 04 '13 at 08:25

1

The results array needs to be declared and initialized (probably as a local variable in the doInBackground(String) method):

String[] results = new String[5];

answered Dec 04 '13 at 08:25

Justin Muller

1,283
13
21

I initialized it, but nothing changed – roa.tah Dec 04 '13 at 08:48

score 0 · Answer 2 · answered Dec 04 '13 at 08:23

0

It seems like you did not initialize String[] results before you called it. Hence causing the NullPointerException.

answered Dec 04 '13 at 08:23

cokeby190

609
7
14

score 0 · Answer 3 · answered Dec 04 '13 at 08:26

0

You have to initialize your String Array like this : String[] results = new String[5];

answered Dec 04 '13 at 08:26

Arthur Rey

2,990
3
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Infinite Recursion · Answer 4 · 2013-12-04T08:44:54.747

0

results must be null. Null-check and initialize as below:

            Log.d("tem22","tem22="+t);
            if (results == null ) { //null-check
                   results = new String[5];  //initialize
            }
            results[0]=t;
            Log.d("results[0]=","results[0]"+results[0]);
            results[1]=String.valueOf(pressure);
            results[2]=String.valueOf(humm);
            results[3]=String.valueOf(wind);
            results[4]=String.valueOf(desc);

To avoid such exceptions, it is better to configure your IDE to warn you about potential null de-referencing

(e.g in Eclipse -> Preferences -> Java -> Compiler -> Errors -> Warnings ->Null analysis)

edited Dec 04 '13 at 08:44

answered Dec 04 '13 at 08:27

Infinite Recursion

6,511
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You should always avoid Null-check. http://stackoverflow.com/questions/271526/avoiding-null-statements-in-java – Arthur Rey Dec 04 '13 at 08:37
Adding proper null check validations is a Java best practice : https://www.google.co.in/#q=java.lang.NullPointerException+best+practices – Infinite Recursion Dec 04 '13 at 09:01

NullPointerException when using Aysnctask in android

4 Answers4