EditText設置點擊按鈕顯示與隱藏密碼

private void showOrHidePasswd() {
        if (showOrHidePasswd) {
            //設置EditText文本爲可見的
            et_bank_num.setTransformationMethod(HideReturnsTransformationMethod.getInstance());
        } else {
            //設置EditText文本爲隱藏的
            et_bank_num.setTransformationMethod(PasswordTransformationMethod.getInstance());
        }
        showOrHidePasswd = !showOrHidePasswd;
        et_bank_num.postInvalidate();
        //切換後將EditText光標置於末尾
        CharSequence charSequence = et_bank_num.getText();
        if (charSequence instanceof Spannable) {
            Spannable spanText = (Spannable) charSequence;
            Selection.setSelection(spanText, charSequence.length());
        }
    }