Question

I have 2 edittext fields empty and i want to when i type numbers inside the two fields a 3rd textview will automatically get the division of the 2 above edittexts. So no buttons to calculate that etc.

The thing is when i enter one number on any field the app gets force closed. Here is my code and the logcat:

    amount.addTextChangedListener(new TextWatcher() {

        public void afterTextChanged(Editable arg0) {
        }

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

        public void onTextChanged(CharSequence s, int start, int before,
                int count) {
            AddFuelActivity.this.updateValue();
        }

    });

    litres.addTextChangedListener(new TextWatcher() {

        public void afterTextChanged(Editable arg0) {
        }

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

        public void onTextChanged(CharSequence s, int start, int before,
                int count) {
            AddFuelActivity.this.updateValue();
        }

    });


protected void updateValue() {
    int amountInt = Integer.parseInt(amount.getText().toString());
    int litresInt = Integer.parseInt(litres.getText().toString());
    float priceFuelAuto = 0;
    priceFuelAuto = amountInt / litresInt;
    fuelPrice.setText("€ " + priceFuelAuto);
}

logcat errors: i think these are the important ones.

01-22 13:23:21.650: E/AndroidRuntime(671): java.lang.NumberFormatException: Invalid int: ""
01-22 13:23:21.650: E/AndroidRuntime(671):  at java.lang.Integer.invalidInt(Integer.java:138)
01-22 13:23:21.650: E/AndroidRuntime(671):  at java.lang.Integer.parseInt(Integer.java:359)
01-22 13:23:21.650: E/AndroidRuntime(671):  at java.lang.Integer.parseInt(Integer.java:332)
01-22 13:23:21.650: E/AndroidRuntime(671):  atcom.example.mycarfuel.AddFuelActivity.updateValue(AddFuelActivity.java:155)
01-22 13:23:21.650: E/AndroidRuntime(671):  atcom.example.mycarfuel.AddFuelActivity$2.onTextChanged(AddFuelActivity.java:67)

I fixed my code. Here is what i did:

    public void onTextChanged(CharSequence s, int start, int before,
            int count) {
        if (litres.length() > 0) {
            AddFuelActivity.this.updateValue();
        }
    }

and

    int amountInt = 0;
    int litresInt = 0;
    try {
        amountInt = Integer.parseInt(amount.getText().toString());
        litresInt = Integer.parseInt(litres.getText().toString());
    } catch (NumberFormatException e) {
        litresInt = 0;
        amountInt = 0;
    }
    if(amountInt !=0 && litresInt != 0){
        float priceFuelAuto = 0;
        priceFuelAuto = amountInt / litresInt;
        fuelPrice.setText("€ " + priceFuelAuto);
    }

thank you for your replies people

Answer 1

@Override
        public void onTextChanged(CharSequence s, int start, int before,
                int count) {
            // TODO Auto-generated method stub
            if(edittext1.length()!=0){
            updateValue() 

            }
            else{
                edittext2.setText("");
            }