How do I use the TransformationMethod interface?

Question

I want to create an EditText which accepts passwords. I want to hide the character as soon as it is typed. So I tried to implement the TransformationMethod interface.

I am new to this. I tried the following code:

EditText editText = (EditText) findViewById(R.id.editText);
editText.setTransformationMethod(new PasswordTransformationMethod());

private class PasswordTransformationMethod implements TransformationMethod {

    @Override
    public CharSequence getTransformation(CharSequence source, View view) {
        return "/";
    }

    @Override
    public void onFocusChanged(View view, CharSequence source, boolean focused, int direction, Rect previouslyFocusedRect) {
        source = getTransformation(source, view);
    }
}

However, it throws java.lang.IndexOutOfBoundsException.

I am missing something. Any help will be appreciated.

Answer 1

Here is an example implementation of the PasswordTransformationMethod class that I use to convert passwords into dots:

public class MyPasswordTransformationMethod extends PasswordTransformationMethod {

    @Override
    public CharSequence getTransformation(CharSequence source, View view) {
        return new PasswordCharSequence(source);
    }

    private class PasswordCharSequence implements CharSequence {

        private CharSequence mSource;

        public PasswordCharSequence(CharSequence source) {
            mSource = source; 
        }

        public char charAt(int index) {
            return '.'; 
        }

        public int length() {
            return mSource.length(); 
        }

        public CharSequence subSequence(int start, int end) {
            return mSource.subSequence(start, end); // Return default
        }
    }
};

You add it to an EditText like this:

passwordEditText = (EditText) findViewById(R.id.passwordEditText);
passwordEditText.setTransformationMethod(new MyPasswordTransformationMethod());