Android error in postExecute method URL parameters not adding in mysql database

Question

i'm trying to run an activity in order to submit all text information to mysql database and start a new activity but I always get unfortunately, app has stopped

here is DonateFood.java activity

public class DonateFood extends AppCompatActivity {

EditText txt_title, txt_desc, txt_amount, txt_date;
Spinner statuss;
Button btnSubmit;
String array;
String title, amount, desc, date, status;

Context con;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_donate_food);

    txt_title = (EditText)findViewById(R.id.txt_title);
    txt_amount = (EditText)findViewById(R.id.txt_amount);
    txt_desc = (EditText)findViewById(R.id.txt_desc);
    txt_date = (EditText)findViewById(R.id.txt_date);
    statuss = (Spinner)findViewById(R.id.status);
    btnSubmit = (Button) findViewById(R.id.btnSubmit);

    statuss.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {

            array=adapterView.getSelectedItem().toString();
        }

        @Override
        public void onNothingSelected(AdapterView<?> adapterView) {

        }
    });

    btnSubmit.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            title =  txt_title.getText().toString();
            amount = txt_amount.getText().toString();
            desc = txt_desc.getText().toString();
            date = txt_date.getText().toString();

            String method = "addFood";

            AddFood addFood = new AddFood(con);
            addFood.execute(method,title,amount,desc,date,array);


        }
    });
}


public class AddFood extends AsyncTask<String, Void, String> {
    Context ctx;

    final String TAG = this.getClass().getName();

    //constructor
    AddFood(Context ctx){
        this.ctx=ctx;
    }

    @Override
    protected String doInBackground(String... params) {

        String food_url = "http://10.0.3.2/MySqlDemo/addFood.php";

        String method = params[0];
        if(method.equals("addFood")){


            String title = params[1];
            String amount = params[2];
            String desc = params[3];
            String date = params[4];
            String array = params[5];

            try {
                URL url = new URL (food_url);
                HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
                httpURLConnection.setRequestMethod("POST");
                httpURLConnection.setDoOutput(true);
                httpURLConnection.setDoInput(true);
                OutputStream outputStream = httpURLConnection.getOutputStream();
                BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream, "UTF-8"));
                String data = URLEncoder.encode("title", "UTF-8")+"="+URLEncoder.encode(title, "UTF-8")+ "&"
                        +URLEncoder.encode("amount", "UTF-8")+"="+URLEncoder.encode(amount, "UTF-8")+ "&"
                        +URLEncoder.encode("desc", "UTF-8")+"="+URLEncoder.encode(desc, "UTF-8")+ "&"
                        +URLEncoder.encode("date", "UTF-8")+"="+URLEncoder.encode(date, "UTF-8")+ "&"
                        +URLEncoder.encode("array", "UTF-8")+"="+URLEncoder.encode(array, "UTF-8");
                bufferedWriter.flush();
                bufferedWriter.close();
                outputStream.close();
                InputStream inputStream = httpURLConnection.getInputStream();
                inputStream.close();

                return "Food added successfully";


            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }


        }
        return null;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }

    @Override
    protected void onPostExecute(String result) {
        if (result == null) {
            Toast.makeText(ctx,"result was null", Toast.LENGTH_SHORT).show();
            return;
        }

       else if (result.equals("Food added successfully")) {
            Toast.makeText(ctx, result, Toast.LENGTH_SHORT).show();

            ctx.startActivity(new Intent(ctx, FoodView.class));

        }


    }


}

}

the logcat error :

02-24 17:21:45.465 5871-5871/alsaad.layla.mysqldemo E/AndroidRuntime: FATAL EXCEPTION: main
                                                                  java.lang.NullPointerException
                                                                      at android.widget.Toast.<init>(Toast.java:92)
                                                                      at android.widget.Toast.makeText(Toast.java:238)
                                                                      at alsaad.layla.mysqldemo.DonateFood$AddFood.onPostExecute(DonateFood.java:161)
                                                                      at alsaad.layla.mysqldemo.DonateFood$AddFood.onPostExecute(DonateFood.java:90)
                                                                      at android.os.AsyncTask.finish(AsyncTask.java:631)
                                                                      at android.os.AsyncTask.access$600(AsyncTask.java:177)
                                                                      at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
                                                                      at android.os.Handler.dispatchMessage(Handler.java:99)
                                                                      at android.os.Looper.loop(Looper.java:137)
                                                                      at android.app.ActivityThread.main(ActivityThread.java:5041)
                                                                      at java.lang.reflect.Method.invokeNative(Native Method)
                                                                      at java.lang.reflect.Method.invoke(Method.java:511)
                                                                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
                                                                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
                                                                      at dalvik.system.NativeStart.main(Native Method)

Possible duplicate of [What is a NullPointerException, and how do I fix it?](http://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — Bö macht Blau, Feb 24 '17 at 17:54

score 2 · Accepted Answer · answered Feb 24 '17 at 18:00

2

try using getApplicationContext() in your onPostExecute()

Toast.makeText(getApplicationContext(),"result was null", Toast.LENGTH_SHORT).show();

instead of:

Toast.makeText(ctx,"result was null", Toast.LENGTH_SHORT).show();

answered Feb 24 '17 at 18:00

rafsanahmad007

23,683
6
47
62

it worked.. I got another problem, why do I get blank data instead when I add new values to database? help! – layla7 Feb 24 '17 at 18:05
it worked fine.. but when I check my database blank values are added – layla7 Feb 24 '17 at 18:09
check the URL ..and also the `&` qotation – rafsanahmad007 Feb 24 '17 at 18:13
I double checked.. found nothing – layla7 Feb 24 '17 at 18:16
you did not use : `bufferedWriter.write()` to write the parameters see this:http://stackoverflow.com/questions/9767952/how-to-add-parameters-to-httpurlconnection-using-post – rafsanahmad007 Feb 24 '17 at 18:47

score 2 · Answer 2 · answered Feb 24 '17 at 18:00

2

Kindly initialize Context object

con = getApplicationContext();

answered Feb 24 '17 at 18:00

Aman

458
4
16

score 0 · Answer 3 · answered Feb 24 '17 at 17:59

0

Your problem is that the application could not get the Context in the application. It is not initialized anywhere and to display a toast we need to pass a context to it which is not null;

  Context con;

In onCreate method, just initialize the application context as

  con = getApplicationContext;

or just simply

  con = this;

answered Feb 24 '17 at 17:59

Vikas Pal

58
9

it worked.. I got another problem, why do I get blank data instead when I add new values? help! – layla7 Feb 24 '17 at 18:02
@layla7 You mean the data does not get inserted properly into the database. There might be some problem with the URL encoding that you are passing into the URL. – Vikas Pal Feb 24 '17 at 18:07

score 0 · Answer 4 · answered Feb 24 '17 at 18:01

I think you're not initialising the variable "con" so it is always null, you can initialise your variable "con" in your onCreate method:

@Override
protected void onCreate(Bundle savedInstanceState) {
    ... 
    con = this;
    ...
}

or you can delete your variable "con" and do something like this on your btnSubmit onClik listener

AddFood addFood = new AddFood(DonateFood.this);
addFood.execute(method,title,amount,desc,date,array);

score 0 · Answer 5 · answered Feb 24 '17 at 18:07

0

You are not initializing your Context object. In oncreate method.Just add this line : con = getApplicationContext(); Also,Since you are within main activity class.You can use getApplicationContext() directly.

answered Feb 24 '17 at 18:07

Jack

308
6
15

Android error in postExecute method URL parameters not adding in mysql database

5 Answers5