Detect when user enters data into edittext immediately shows answer

Question

How is it possible to detect if a character is inputted into an EditText which makes it from 0 to 1 characters long and then perform some action?

Accepted Answer

Since you have a rather abstract question, let me attempt an equally generic answer:

In your `onCreate()`, declare and cast your `EditText`

```
EditText editText = (EditText) findViewById(R.id.editText);
editText.addTextChangedListener(filterTextWatcher);
```

And then, outside the `onCreate()`, setup the `filterTextWatcher` like this:

```
private TextWatcher filterTextWatcher = new TextWatcher() {

@Override
    public void onTextChanged(CharSequence s, int start, int before, int count) {
        // DO THE CALCULATIONS HERE AND SHOW THE RESULT AS PER YOUR CALCULATIONS

int radius = 0;
        radius = Integer.valueof(s.toString);
        double area = Math.PI * radius * radius;
    }

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

}

@Override
    public void afterTextChanged(Editable s) {

}
};
```

EDIT:

Updated code with possible calculation. (UNTESTED CODE: I JUST TYPED IT IN WITHOUT TESTING IT. MODIFY WHERE NECESSARY)

Detect when user enters data into edittext immediately shows answer

Solution

Problem