Editextのパスワードの表示と非表示

private void showPassword() {
    if (isHidden) {
        //  
        et_wifiPwd.setTransformationMethod(HideReturnsTransformationMethod.getInstance());
    } else {
        //  
        et_wifiPwd.setTransformationMethod(PasswordTransformationMethod.getInstance());
    }
    isHidden = !isHidden;
    et_wifiPwd.postInvalidate();
    //    EditText      
    CharSequence charSequence = et_wifiPwd.getText();
    if (charSequence instanceof Spannable) {
        Spannable spanText = (Spannable) charSequence;
        Selection.setSelection(spanText, charSequence.length());
    }
}