editText validation and correction with TextWatcher

Question

I'm very beginner to programming in android. Sorry if my question is obvious.

I have an editText with inputType="numberDecimal". I watch it's changes with TextWatcher, calculating from it's value (Double type), and show it on a TextView. The calculation is OK, except if the editText has the value ".". If the editText has the value ".", the program drops an error (force close).

My question is: how can I set the editText value to "0." with the use of addTextChangedListener if the editText gets the value "."? Have You got for this situacion a best practice? Thanks in advance for Your help.

My code is:

public class ConversionsFragment extends Fragment{

    private EditText etDistBase;
    private TextView tvMeterResult;
    private TextView tvKmResult;

   @Override
   public View onCreateView(LayoutInflater inflater, ViewGroup container, 
           Bundle savedInstanceState) {

       View rootView = inflater.inflate(R.layout.fragment_conversions, container, false);

       etDistBase = (EditText) rootView.findViewById(R.id.textEdit_conv_distance);
       tvMeterResult = (TextView) rootView.findViewById(R.id.conv_dist_result_meter);
       tvKmResult = (TextView) rootView.findViewById(R.id.conv_dist_result_km);

       etDistBase.addTextChangedListener(new TextWatcher(){
            public void afterTextChanged(Editable s) {

            } 
            public void beforeTextChanged(CharSequence s, int start, int count, int after){

            }
            public void onTextChanged(CharSequence s, int start, int before, int count){
                   calculateConvDistances(); 
            }
        });
       return rootView;

   }


   private void calculateConvDistances() {

       String baseText = etDistBase.getText().toString();
       Double baseValue = 0.0,
              meterResult = 0.0,
              kmResult = 0.0;

//     if (baseText == ".") {
//         etDistBase.setText("0.");
//         baseText = "0";
//     }

       if (baseText.length() == 0)
               baseText = "0";

       if (baseText != null) {
            baseValue = Double.parseDouble(baseText);
            meterResult = baseValue * 1000;
            kmResult = baseValue;
       } else {
           meterResult = 0.0;
           kmResult = 0.0;
       }

      tvMeterResult.setText(Double.toString(meterResult));
      tvKmResult.setText(Double.toString(kmResult));

    } 

}

Answer 1

Try with this

if( editText.getText().toString().equals(".") ){
    editText.setText("0.");
}

write into the afterTextChanged() method.

Answer 2

The working solution was to change the "." text to "0." in the afterTextChanged() method, as follows:

public class ConversionsFragment extends Fragment{

    private EditText etDistBase;
    private TextView tvMeterResult;
    private TextView tvKmResult;

   @Override
   public View onCreateView(LayoutInflater inflater, ViewGroup container, 
           Bundle savedInstanceState) {

       View rootView = inflater.inflate(R.layout.fragment_conversions, container, false);

       etDistBase = (EditText) rootView.findViewById(R.id.textEdit_conv_distance);
       tvMeterResult = (TextView) rootView.findViewById(R.id.conv_dist_result_meter);
       tvKmResult = (TextView) rootView.findViewById(R.id.conv_dist_result_km);

       etDistBase.addTextChangedListener(new TextWatcher(){
            public void afterTextChanged(Editable s) {
                if (etDistBase.getText().toString().equals(".")) 
                    etDistBase.setText("0.");
                    etDistBase.setSelection(etDistBase.getText().length());
            } 
            public void beforeTextChanged(CharSequence s, int start, int count, int after){

            }
            public void onTextChanged(CharSequence s, int start, int before, int count){
                    calculateConvDistances(); 
            }
        });
       return rootView;

   }


   private void calculateConvDistances() {

       String baseText = etDistBase.getText().toString();
       Double baseValue = 0.0,
              meterResult = 0.0,
              kmResult = 0.0;

       if (baseText.equals(".")) {
           baseText = "0";
       }

       if (baseText.length() == 0)
               baseText = "0";

       if (baseText != null) {
            baseValue = Double.parseDouble(baseText);
            meterResult = baseValue * 1000;
            kmResult = baseValue;
       } else {
           meterResult = 0.0;
           kmResult = 0.0;
       }

      tvMeterResult.setText(Double.toString(meterResult));
      tvKmResult.setText(Double.toString(kmResult));

    } 

}