android:compileSdkVersion="23" => android:compileSdkVersion="26"
platformBuildVersionCode="23" => platformBuildVersionCode="26"
----------------------------------------------------------------
Sau khi đổi build ra thì nó lại về 23 như cũ.

<?xml version="1.0" encoding="utf-8" standalone="no"?><manifest xmlns:android="http://schemas.android.com/apk/res/android" android:compileSdkVersion="23" android:compileSdkVersionCodename="6.0-2438415" package="app.com.ngontinhngoaitruyen" platformBuildVersionCode="23" platformBuildVersionName="6.0-2438415">
    <uses-permission android:name="android.permission.WRITE_SETTINGS"/>
    <uses-permission android:name="android.permission.INTERNET"/>
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
    <uses-permission android:name="android.permission.CHANGE_CONFIGURATION"/>
    <application android:allowBackup="true" android:icon="@drawable/ic3" android:label="@string/app_name" android:supportsRtl="true" android:theme="@style/AppTheme">
        <activity android:configChanges="keyboardHidden|orientation" android:name="app.com.ngontinhngoaitruyen.activity.MainActivity" android:screenOrientation="portrait" android:theme="@style/Theme.AppCompat.Light.NoActionBar.FullScreen">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>
        <activity android:name="app.com.ngontinhngoaitruyen.activity.ListCat" android:theme="@style/Theme.AppCompat.Light.NoActionBar.FullScreen"/>
        <activity android:configChanges="keyboardHidden|orientation" android:name="app.com.ngontinhngoaitruyen.activity.DocTruyenActivity" android:screenOrientation="portrait" android:theme="@style/Theme.AppCompat.Light.NoActionBar.FullScreen"/>
        <activity android:configChanges="keyboardHidden|orientation" android:name="app.com.ngontinhngoaitruyen.activity.DetailCat" android:screenOrientation="portrait" android:theme="@style/Theme.AppCompat.Light.NoActionBar.FullScreen"/>
        <activity android:configChanges="keyboard|keyboardHidden|orientation|screenLayout|screenSize|smallestScreenSize|uiMode" android:name="com.google.android.gms.ads.AdActivity" android:theme="@android:style/Theme.Translucent"/>
        <activity android:name="com.google.android.gms.ads.purchase.InAppPurchaseActivity" android:theme="@style/Theme.IAPTheme"/>
        <meta-data android:name="com.google.android.gms.version" android:value="@integer/google_play_services_version"/>
    </application>
</manifest>