這還滿神奇的，有2個解法，一個是

Just for the people who are having same problem. Just add an extra attribute to that EditText programmatically and you are done.

password.setInputType(InputType.TYPE_CLASS_TEXT |
InputType.TYPE_TEXT_VARIATION_PASSWORD);

use this code to change password to text and vice versa

mCbShowPwd.setOnCheckedChangeListener(new OnCheckedChangeListener() {

            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                // checkbox status is changed from uncheck to checked.
                if (!isChecked) {
                        // show password
                    mEtPwd.setTransformationMethod(PasswordTransformationMethod.getInstance());
                } else {
                        // hide password
                    mEtPwd.setTransformationMethod(HideReturnsTransformationMethod.getInstance());
                }
            }
        });

for full sample code refer http://www.codeproject.com/Tips/518641/Show-hide-password-in-a-edit-text-view-password-ty