How to write xpath to identify the username textField? and Why the textField can't be identified by Inspector?

how to write xpath to identify the username textField?

I click the Username textField, inspector shows that a Button:

but, in source code, it is a textField

    <objects>
    <placeholder placeholderIdentifier="IBFilesOwner" id="-1" userLabel="File's Owner" customClass="LoginViewController">
        <connections>
            <outlet property="containerScrollView" destination="10" id="12"/>
            <outlet property="loginBtn" destination="11" id="16"/>
            <outlet property="loginImg" destination="4" id="18"/>
            <outlet property="loginInformationView" destination="7" id="20"/>
            <outlet property="passwordTextField" destination="8" id="14"/>
            <outlet property="saveIdLable" destination="23" id="28"/>
            <outlet property="saveSwitch" destination="24" id="27"/>
            <outlet property="usernameTextField" destination="5" id="15"/>
            <outlet property="view" destination="1" id="3"/>
        </connections>
    </placeholder>
    <placeholder placeholderIdentifier="IBFirstResponder" id="-2" customClass="UIResponder"/>
    <view contentMode="scaleToFill" id="1" customClass="UIButton">
        <rect key="frame" x="0.0" y="20" width="320" height="460"/>
        <autoresizingMask key="autoresizingMask" flexibleMinX="YES" widthSizable="YES" flexibleMaxX="YES" flexibleMinY="YES" heightSizable="YES" flexibleMaxY="YES"/>
        <subviews>
            <view contentMode="scaleToFill" id="70z-zY-PBR">
                <rect key="frame" x="0.0" y="0.0" width="320" height="460"/>
                <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                <subviews>
                    <imageView userInteractionEnabled="NO" contentMode="scaleToFill" horizontalHuggingPriority="251" verticalHuggingPriority="251" id="FKH-QJ-bX1">
                        <rect key="frame" x="0.0" y="-20" width="320" height="20"/>
                        <autoresizingMask key="autoresizingMask" widthSizable="YES" flexibleMaxY="YES"/>
                        <color key="backgroundColor" red="0.41568627450980389" green="0.41568627450980389" blue="0.42745098039215684" alpha="1" colorSpace="calibratedRGB"/>
                    </imageView>
                    <scrollView clipsSubviews="YES" multipleTouchEnabled="YES" contentMode="scaleToFill" id="10">
                        <rect key="frame" x="0.0" y="0.0" width="320" height="460"/>
                        <autoresizingMask key="autoresizingMask" flexibleMinX="YES" widthSizable="YES" flexibleMaxX="YES" flexibleMinY="YES" heightSizable="YES" flexibleMaxY="YES"/>
                        <subviews>
                            <view contentMode="scaleToFill" id="XCF-Qh-WL5">
                                <rect key="frame" x="0.0" y="0.0" width="320" height="179"/>
                                <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMaxY="YES"/>
                                <subviews>
                                    <imageView userInteractionEnabled="NO" contentMode="scaleToFill" image="manager_logo.png" id="4">
                                        <rect key="frame" x="20" y="45" width="280" height="90"/>
                                        <autoresizingMask key="autoresizingMask" widthSizable="YES" flexibleMaxY="YES"/>
                                    </imageView>
                                </subviews>
                                <color key="backgroundColor" white="1" alpha="1" colorSpace="custom" customColorSpace="calibratedWhite"/>
                            </view>
                            <view contentMode="scaleToFill" id="7">
                                <rect key="frame" x="0.0" y="179" width="335" height="71"/>
                                <autoresizingMask key="autoresizingMask" flexibleMinX="YES" widthSizable="YES" flexibleMaxX="YES" flexibleMaxY="YES"/>
                                <subviews>
                                    <view contentMode="scaleToFill" id="IGA-wW-Ubv" userLabel="line1">
                                        <rect key="frame" x="0.0" y="0.0" width="335" height="1"/>
                                        <autoresizingMask key="autoresizingMask" widthSizable="YES" flexibleMaxX="YES" flexibleMaxY="YES"/>
                                        <color key="backgroundColor" white="0.66666666666666663" alpha="0.22" colorSpace="calibratedWhite"/>
                                    </view>
                                    <textField opaque="NO" clipsSubviews="YES" tag="1" contentMode="scaleToFill" contentHorizontalAlignment="left" contentVerticalAlignment="center" placeholder="UserName" minimumFontSize="17" clearButtonMode="always" id="5">
                                        <rect key="frame" x="15" y="0.0" width="290" height="35"/>
                                        <autoresizingMask key="autoresizingMask" widthSizable="YES" flexibleMaxX="YES" flexibleMaxY="YES"/>
                                        <fontDescription key="fontDescription" type="system" pointSize="17"/>
                                        <textInputTraits key="textInputTraits" keyboardType="emailAddress" returnKeyType="next"/>
                                    </textField>
                                    <view contentMode="scaleToFill" id="v28-K1-aEt" userLabel="line2">
                                        <rect key="frame" x="0.0" y="35" width="335" height="1"/>
                                        <autoresizingMask key="autoresizingMask" widthSizable="YES" flexibleMaxX="YES" flexibleMinY="YES" flexibleMaxY="YES"/>
                                        <color key="backgroundColor" white="0.66666666666666663" alpha="0.22" colorSpace="calibratedWhite"/>
                                    </view>
                                    <textField opaque="NO" clipsSubviews="YES" tag="2" contentMode="scaleToFill" contentHorizontalAlignment="left" contentVerticalAlignment="center" placeholder="Password" minimumFontSize="17" clearButtonMode="always" id="8">
                                        <rect key="frame" x="15" y="36" width="290" height="35"/>
                                        <autoresizingMask key="autoresizingMask" widthSizable="YES" flexibleMaxX="YES" flexibleMinY="YES" flexibleMaxY="YES"/>
                                        <fontDescription key="fontDescription" type="system" pointSize="17"/>
                                        <textInputTraits key="textInputTraits" returnKeyType="join" secureTextEntry="YES"/>
                                    </textField>
                                </subviews>
                                <color key="backgroundColor" white="1" alpha="1" colorSpace="calibratedWhite"/>
                            </view>
                            <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" lineBreakMode="middleTruncation" id="11">
                                <rect key="frame" x="7" y="300" width="307" height="46"/>
                                <autoresizingMask key="autoresizingMask" flexibleMinX="YES" widthSizable="YES" flexibleMaxX="YES"/>
                                <rect key="contentStretch" x="0.5" y="0.5" width="0.5" height="0.49999999999999961"/>
                                <fontDescription key="fontDescription" type="boldSystem" pointSize="18"/>
                                <state key="normal" title="Login">
                                    <color key="titleColor" white="1" alpha="1" colorSpace="calibratedWhite"/>
                                    <color key="titleShadowColor" white="0.5" alpha="1" colorSpace="calibratedWhite"/>
                                </state>
                                <state key="highlighted">
                                    <color key="titleColor" white="0.66666666666666663" alpha="1" colorSpace="calibratedWhite"/>
                                </state>
                                <connections>
                                    <action selector="tapOnLoginBtn:" destination="-1" eventType="touchUpInside" id="33"/>
                                </connections>
                            </button>
                            <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" lineBreakMode="middleTruncation" id="kkO-HN-x8f">
                                <rect key="frame" x="7" y="350" width="307" height="44"/>
                                <autoresizingMask key="autoresizingMask" flexibleMinX="YES" widthSizable="YES" flexibleMaxX="YES"/>
                                <fontDescription key="fontDescription" type="boldSystem" pointSize="18"/>
                                <state key="normal" title="Enable Single Sign-On">
                                    <color key="titleShadowColor" white="0.5" alpha="1" colorSpace="calibratedWhite"/>
                                </state>
                                <connections>
                                    <action selector="onSSOLoginClicked:" destination="-1" eventType="touchUpInside" id="85U-Mr-kfO"/>
                                </connections>
                            </button>
                            <label opaque="NO" clipsSubviews="YES" userInteractionEnabled="NO" contentMode="left" text="Save Username" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" minimumFontSize="10" adjustsFontSizeToFit="NO" id="23">
                                <rect key="frame" x="15" y="260" width="138" height="27"/>
                                <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMaxY="YES"/>
                                <fontDescription key="fontDescription" type="system" pointSize="17"/>
                                <color key="textColor" white="1" alpha="1" colorSpace="calibratedWhite"/>
                                <nil key="highlightedColor"/>
                            </label>
                            <switch autoresizesSubviews="NO" opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" on="YES" id="24">
                                <rect key="frame" x="161" y="260" width="79" height="27"/>
                                <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMaxY="YES"/>
                                <color key="backgroundColor" white="0.0" alpha="0.0" colorSpace="calibratedWhite"/>
                            </switch>
                        </subviews>
                        <color key="backgroundColor" white="0.0" alpha="0.0" colorSpace="calibratedWhite"/>
                    </scrollView>
                </subviews>
                <color key="backgroundColor" red="0.81568627450980391" green="0.12156862745098039" blue="0.16078431372549018" alpha="1" colorSpace="calibratedRGB"/>
                <inset key="insetFor6xAndEarlier" minX="0.0" minY="20" maxX="0.0" maxY="-20"/>
            </view>
        </subviews>
        <color key="backgroundColor" white="0.0" alpha="1" colorSpace="calibratedWhite"/>
        <simulatedScreenMetrics key="simulatedDestinationMetrics"/>
        <point key="canvasLocation" x="221" y="263"/>
    </view>
</objects>

if I copy XML from inspector, got xml as below

     <?xml version="1.0" encoding="UTF-8"?>
<AppiumAUT>
    <UIAApplication name="Manager" label="Manager" value="" dom="" enabled="true" valid="true" visible="true" hint="" path="/0" x="0" y="20" width="320" height="548">
        <UIAWindow name="" label="" value="" dom="" enabled="true" valid="true" visible="true" hint="" path="/0/0" x="0" y="0" width="320" height="568">
            <UIAButton name="" label="" value="" dom="" enabled="true" valid="true" visible="true" hint="" path="/0/0/0" x="0" y="0" width="320" height="568">
            </UIAButton>
        </UIAWindow>
        <UIAWindow name="" label="" value="" dom="" enabled="true" valid="true" visible="false" hint="" path="/0/1" x="0" y="0" width="320" height="568">
        </UIAWindow>
        <UIAWindow name="" label="" value="" dom="" enabled="true" valid="true" visible="true" hint="" path="/0/2" x="0" y="0" width="320" height="568">
            <UIAStatusBar name="" label="" value="" dom="" enabled="true" valid="true" visible="true" hint="" path="/0/2/0" x="0" y="0" width="320" height="20">
                <UIAElement name="Swipe down with three fingers to reveal the notification center., Swipe up with three fingers to reveal the control center, Double-tap to scroll to top" label="" value="" dom="" enabled="true" valid="true" visible="true" hint="Swipe down with three fingers to reveal the notification center., Swipe up with three fingers to reveal the control center, Double-tap to scroll to top" path="/0/2/0/0" x="6" y="0" width="38" height="20">
                </UIAElement>
                <UIAElement name="3 of 3 Wi-Fi bars" label="3 of 3 Wi-Fi bars" value="" dom="" enabled="true" valid="true" visible="true" hint="Swipe down with three fingers to reveal the notification center., Swipe up with three fingers to reveal the control center, Double-tap to scroll to top" path="/0/2/0/1" x="49" y="0" width="13" height="20">
                </UIAElement>
                <UIAElement name="1:13 PM" label="1:13 PM" value="" dom="" enabled="true" valid="true" visible="true" hint="Swipe down with three fingers to reveal the notification center., Swipe up with three fingers to reveal the control center, Double-tap to scroll to top" path="/0/2/0/2" x="138" y="0" width="44" height="20">
                </UIAElement>
                <UIAElement name="100% battery power" label="100% battery power" value="" dom="" enabled="true" valid="true" visible="true" hint="Swipe down with three fingers to reveal the notification center., Swipe up with three fingers to reveal the control center, Double-tap to scroll to top" path="/0/2/0/3" x="290" y="0" width="25" height="20">
                </UIAElement>
            </UIAStatusBar>
        </UIAWindow>
    </UIAApplication>
</AppiumAUT>

how should I identify the textField???

Did you ever figure this out?