EditText not changing correctly

Question

I am new to Stackoverflow.

I am trying to make a Unit Converter in which the function "calculateCurrency" returns a Double value of the result. But the value of TextView "outputNumber" is always changing based on the previous input.

Ex- If I type 1, then the outputNumber is changed to "null" but when I enter another digit after 1, then the outputNumber changes to the value it was supposed to be changed on 1. But the Toast is displaying the correct value i.e. on 1, it is displaying 1 so the value of myInputNumber is correct according to the input.

Can anyone help me?

inputNumber.addTextChangedListener(
            new TextWatcher() {
                @Override
                public void beforeTextChanged(CharSequence s, int start, int count, int after) {
                }

                @Override
                public void onTextChanged(CharSequence s, int start, int before, int count) {
                }

                @Override
                public void afterTextChanged(Editable s) {
                    try {
                        myInputNumber = Double.parseDouble(s.toString());
                        Double myText = calculations.calculateCurrency(myInputNumber, convertFrom, convertTo);
                        Toast.makeText(MainActivity.this, myInputNumber+"", Toast.LENGTH_SHORT).show();
                        outputNumber.setText(myText+"");
                    } catch (ExecutionException e) {
                        e.printStackTrace();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    } catch (Exception e){
                        e.printStackTrace();
                    }
                }
            }
    );

The code of calculations.calculateCurrency is:

 public Double calculateCurrency(Double input, String convertFrom, String convertTo) throws ExecutionException, InterruptedException {
        myCurrencyFetcher fetchCurrency = new myCurrencyFetcher();
        fetchCurrency.execute(Double.toString(input), convertFrom, convertTo);
        return myText;
}


class myCurrencyFetcher extends AsyncTask<String, Double, Double>{

    URL url;
    StringBuffer stringBuffer;

    @Override
    protected Double doInBackground(String... params) {
        try{
            Double myInputNumber = Double.parseDouble(params[0]);
            String convertFrom = params[1];
            String convertTo = params[2];
            url = new URL("http://api.fixer.io/latest?base="+convertFrom+"&symbols="+convertTo);

            HttpURLConnection connection;
                connection = (HttpURLConnection) url.openConnection();
                connection.connect();

                InputStream inputStream = connection.getInputStream();

                BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));

                stringBuffer = new StringBuffer();

                String line = "";
                while((line = reader.readLine()) != null){
                    stringBuffer.append(line);
                }
            String finalJSON = stringBuffer.toString();

            JSONObject parentObject = new JSONObject(finalJSON);
            JSONObject finalObject = parentObject.getJSONObject("rates");

            String rate = finalObject.getString(convertTo);
            //String year = finalObject.getString("year");
            Double myRate = Double.parseDouble(rate);

            return myInputNumber*myRate;
            } catch (Exception e) {
                e.printStackTrace();
            }
        return null;
    }

    @Override
    protected void onPostExecute(Double result) {
        super.onPostExecute(result);
        Calculations.myText = result;
    }
}

Answer 1

You have to change your code.

@Override
    public void afterTextChanged(Editable s) {
        try {
            myInputNumber = Double.parseDouble(s.toString());
            Double myText = calculations.calculateCurrency(myInputNumber, convertFrom, convertTo);
            Toast.makeText(MainActivity.this, myInputNumber+"", Toast.LENGTH_SHORT).show();
            //outputNumber.setText(myText+""); // Remove this line
        } catch (ExecutionException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (Exception e){
            e.printStackTrace();
        }
    }

Add TextView (outputNumber) to Constructor as argument. myCurrencyFetcher fetchCurrency = new myCurrencyFetcher(outputNumber);

class myCurrencyFetcher extends AsyncTask<String, Double, Double>{

 private WeakReference<TextView> weakOutputNumber; 

 public myCurrencyFetcher (TextView outputNumber) {
     weakOutputNumber= new WeakReference<TextView>(outputNumber);
 } 

 /* ... Other methods are the same */

 @Override
    protected void onPostExecute(Double result) {
        super.onPostExecute(result);
        //Calculations.myText = result;
        if (weakOutputNumber != null) {
        TextView outputNumber = weakOutputNumber.get();
           if (outputNumber != null) {
               outputNumber.setText(new String(result));
           }
        }

    }

}