# 📚 Official Books **URL:** https://forums.kodeco.com/c/books/6.md?page=38 [Latest](https://forums.kodeco.com/latest.md) · [Categories](https://forums.kodeco.com/categories.md) · [Tags](https://forums.kodeco.com/tags.md) **Page:** 39 --- ## [Retrofit concepts in Depth](https://forums.kodeco.com/t/retrofit-concepts-in-depth/155852)
**Author:** [@pvr](https://forums.kodeco.com/u/pvr)\ **Replies:** 0\ **Last updated:** [November 3, 2021, 4:53pm UTC](https://forums.kodeco.com/t/retrofit-concepts-in-depth/155852 "2021-11-03T16:53:27Z")
I want to know how to add headers dynamically. And What is an Interceptor, could anyone let me know when to use this. --- ## [How can I develop an image tracking-based AR app?](https://forums.kodeco.com/t/how-can-i-develop-an-image-tracking-based-ar-app/155817)
**Author:** [@alice7890](https://forums.kodeco.com/u/alice7890)\ **Replies:** 0\ **Last updated:** [November 3, 2021, 11:10am UTC](https://forums.kodeco.com/t/how-can-i-develop-an-image-tracking-based-ar-app/155817 "2021-11-03T11:10:26Z")
You can develop an image tracking-based AR app on the PlugXR platform. You can create AR apps with various projects offered by PlugXR. They are: Mobile AR Cloud Image Targets Mobile AR Offline Image Targets WebAR Image… --- ## [Chapter 2 - Function returns a Widget vs Stateless Widget](https://forums.kodeco.com/t/chapter-2-function-returns-a-widget-vs-stateless-widget/155709)
**Author:** [@lanzoninicola](https://forums.kodeco.com/u/lanzoninicola)\ **Replies:** 2\ **Last updated:** [November 3, 2021, 5:01am UTC](https://forums.kodeco.com/t/chapter-2-function-returns-a-widget-vs-stateless-widget/155709 "2021-11-03T05:01:51Z")
Is there a reason for building a function to return the Recipe Card (buildRecipeCard) instead of creating a stateless Widget to render the card? I’m trying to first read the chapter, build it myself, and compare my code… --- ## [8.6 Converting a URL string to an AppLink ... decode vs encode](https://forums.kodeco.com/t/8-6-converting-a-url-string-to-an-applink-decode-vs-encode/155743)
**Author:** [@jefff9511](https://forums.kodeco.com/u/jefff9511)\ **Replies:** 1\ **Last updated:** [November 3, 2021, 1:46am UTC](https://forums.kodeco.com/t/8-6-converting-a-url-string-to-an-applink-decode-vs-encode/155743 "2021-11-03T01:46:06Z")
In 8.6 Converting a URL string to an AppLink I’m confused about encoding and decoding … The text says First, you need to decode the URL. URLs often include special characters in their paths, so you need to percent-enco… --- ## [8.6: AppLink class vs FooderlichPages class](https://forums.kodeco.com/t/8-6-applink-class-vs-fooderlichpages-class/155720)
**Author:** [@jefff9511](https://forums.kodeco.com/u/jefff9511)\ **Replies:** 1\ **Last updated:** [November 3, 2021, 1:38am UTC](https://forums.kodeco.com/t/8-6-applink-class-vs-fooderlichpages-class/155720 "2021-11-03T01:38:09Z")
In Section 8.6, we’ve added the AppLink class. It looks like this will eventually make the FooderlichPages class obsolete. Am I correct or do we need to keep both forever? --- ## [Need exact steps to download the book's sample code](https://forums.kodeco.com/t/need-exact-steps-to-download-the-books-sample-code/155626)
**Author:** [@gncov101](https://forums.kodeco.com/u/gncov101)\ **Replies:** 3\ **Last updated:** [November 2, 2021, 5:25pm UTC](https://forums.kodeco.com/t/need-exact-steps-to-download-the-books-sample-code/155626 "2021-11-02T17:25:53Z")
Hi, When I go to the link for the source code to download it, I see a bunch of file folders and no download button. If this is a “git clone” thing, I am a newbie and need a bit more of a kickstart here to get going. L… --- ## [Duration Function Block Operation](https://forums.kodeco.com/t/duration-function-block-operation/143925)
**Author:** [@amanvedsharma](https://forums.kodeco.com/u/amanvedsharma)\ **Replies:** 1\ **Last updated:** [November 2, 2021, 8:43am UTC](https://forums.kodeco.com/t/duration-function-block-operation/143925 "2021-11-02T08:43:19Z")
Hi, I am not able to understand BlockOperation Playground duration Function in which thread sleeps for 2 seconds for each operation inclusive of 5 operation but whole operation takes 2 sec to complete --- ## [Chapter 6 - How to use nodeJS code?](https://forums.kodeco.com/t/chapter-6-how-to-use-nodejs-code/57101)
**Author:** [@vladimirmalikov](https://forums.kodeco.com/u/vladimirmalikov)\ **Replies:** 1\ **Last updated:** [December 6, 2018, 5:03pm UTC](https://forums.kodeco.com/t/chapter-6-how-to-use-nodejs-code/57101 "2018-12-06T17:03:14Z")
Hi there! Could you explain how to use nodeJS code from chapter 6 for sending notifications from a web server. Let’s say I would like to setup a server on my website and set a schedule for sending notifications there. W… --- ## [Author card giving me errors see screen shot](https://forums.kodeco.com/t/author-card-giving-me-errors-see-screen-shot/153442)
**Author:** [@lc0815](https://forums.kodeco.com/u/lc0815)\ **Replies:** 3\ **Last updated:** [October 30, 2021, 1:58am UTC](https://forums.kodeco.com/t/author-card-giving-me-errors-see-screen-shot/153442 "2021-10-30T01:58:54Z")
the author card favorite button comes up with error that I do not understand can you help LC --- ## [What is the best platform to develop mobile AR apps?](https://forums.kodeco.com/t/what-is-the-best-platform-to-develop-mobile-ar-apps/155520)
**Author:** [@alice7890](https://forums.kodeco.com/u/alice7890)\ **Replies:** 0\ **Last updated:** [November 1, 2021, 5:30am UTC](https://forums.kodeco.com/t/what-is-the-best-platform-to-develop-mobile-ar-apps/155520 "2021-11-01T05:30:03Z")
Augmented reality apps are used very frequently these days. To develop such an application, one must know a great platform for its development. One such great platform is PlugXR. It is a no-code platform where anyone wi… --- ## [What is the difference between diactivate() and dispose()?](https://forums.kodeco.com/t/what-is-the-difference-between-diactivate-and-dispose/155282)
**Author:** [@belalgamal](https://forums.kodeco.com/u/belalgamal)\ **Replies:** 2\ **Last updated:** [October 31, 2021, 7:20am UTC](https://forums.kodeco.com/t/what-is-the-difference-between-diactivate-and-dispose/155282 "2021-10-31T07:20:18Z")
pleas, i couldn’t catch the difference between the diactivate and dispose method in flutter and when the widget is deleted permanently and when it deleted temporarily from the widget tree. can any one help,please? --- ## [Chapter 7: Dismissing the Grocery Item screen](https://forums.kodeco.com/t/chapter-7-dismissing-the-grocery-item-screen/155367)
**Author:** [@matan188](https://forums.kodeco.com/u/matan188)\ **Replies:** 1\ **Last updated:** [October 30, 2021, 6:12am UTC](https://forums.kodeco.com/t/chapter-7-dismissing-the-grocery-item-screen/155367 "2021-10-30T06:12:54Z")
How does the app\_router know to return to the “To Buy” tabs when the user clicks the back button after executing the following in \_handlePopPage if (route.settings.name == FooderlichPages.groceryItemDetails) { gro… --- ## [Out of curiosity](https://forums.kodeco.com/t/out-of-curiosity/155366)
**Author:** [@lc0815](https://forums.kodeco.com/u/lc0815)\ **Replies:** 1\ **Last updated:** [October 30, 2021, 4:33am UTC](https://forums.kodeco.com/t/out-of-curiosity/155366 "2021-10-30T04:33:44Z")
hi there, just out of curiosity, how do include the emojis on the input line, like the salt shaker or the chef’s emoji… it’s not explained anywhere… so its frustrating to see something that is not explained anywhere… it… --- ## [Having problems with the checkbox widget](https://forums.kodeco.com/t/having-problems-with-the-checkbox-widget/155357)
**Author:** [@lc0815](https://forums.kodeco.com/u/lc0815)\ **Replies:** 4\ **Last updated:** [October 30, 2021, 4:31am UTC](https://forums.kodeco.com/t/having-problems-with-the-checkbox-widget/155357 "2021-10-30T04:31:51Z")
hello, i am having problems with the checkbox widget as described in ch06 I can not get the onComplete to work with the code as described and can not figure out why… --- ## [Is AR on mobile apps the next big thing?](https://forums.kodeco.com/t/is-ar-on-mobile-apps-the-next-big-thing/155285)
**Author:** [@alice7890](https://forums.kodeco.com/u/alice7890)\ **Replies:** 0\ **Last updated:** [October 29, 2021, 10:18am UTC](https://forums.kodeco.com/t/is-ar-on-mobile-apps-the-next-big-thing/155285 "2021-10-29T10:18:37Z")
Augmented reality, being immersive and interactive technology, is paving the way for new mobile AR apps that are going to transform the internet market. Every single brand now finds it surprising that this technology is … --- ## [Lifepo4 prismatic cells](https://forums.kodeco.com/t/lifepo4-prismatic-cells/155235)
**Author:** [@melasta836](https://forums.kodeco.com/u/melasta836)\ **Replies:** 0\ **Last updated:** [October 28, 2021, 11:18pm UTC](https://forums.kodeco.com/t/lifepo4-prismatic-cells/155235 "2021-10-28T23:18:34Z")
Melasta battery cells are shot together to make great mechanical associations, getting excellent conductivity and ensuring an unrivaled quality lifepo4 prismatic cells battery. Our shot cells associate the Battery Manage… --- ## [Font Issue on Linux](https://forums.kodeco.com/t/font-issue-on-linux/154967)
**Author:** [@grading-retainer](https://forums.kodeco.com/u/grading-retainer)\ **Replies:** 3\ **Last updated:** [October 28, 2021, 12:37pm UTC](https://forums.kodeco.com/t/font-issue-on-linux/154967 "2021-10-28T12:37:16Z")
In chapter 2, the font “Palatino” is used. When building the app on a Linux system (PopOS) this font does not seem to be installed. When a font is not found in Flutter it gives an ugly error (nothing related to fonts but… --- ## [Adding Modal Dialogs into the projects](https://forums.kodeco.com/t/adding-modal-dialogs-into-the-projects/154898)
**Author:** [@muratursavas](https://forums.kodeco.com/u/muratursavas)\ **Replies:** 3\ **Last updated:** [October 28, 2021, 6:53am UTC](https://forums.kodeco.com/t/adding-modal-dialogs-into-the-projects/154898 "2021-10-28T06:53:59Z")
First and foremost, thanks for writing such a good book and sharing with us. It really helps for getting out the tutorial valley. My question is, how can I add modal dialogs to one of the example projects (let’s say nav… --- ## [How do you develop an AR app?](https://forums.kodeco.com/t/how-do-you-develop-an-ar-app/155139)
**Author:** [@alice7890](https://forums.kodeco.com/u/alice7890)\ **Replies:** 0\ **Last updated:** [October 28, 2021, 6:22am UTC](https://forums.kodeco.com/t/how-do-you-develop-an-ar-app/155139 "2021-10-28T06:22:52Z")
AR apps can be developed using coding languages. It is a tiring and technical job. Therefore, a platform was established to make this job easy and fun. PlugXR, an augmented reality solution platform allowing users to cre… --- ## [iOS Apprentice My Locations app PhotoID issue](https://forums.kodeco.com/t/ios-apprentice-my-locations-app-photoid-issue/155135)
**Author:** [@titkonen](https://forums.kodeco.com/u/titkonen)\ **Replies:** 0\ **Last updated:** [October 28, 2021, 5:49am UTC](https://forums.kodeco.com/t/ios-apprentice-my-locations-app-photoid-issue/155135 "2021-10-28T05:49:36Z")
Hi there! I am learning Swift coding and did MyLocations iOS app demo from book. I now try to expand it in same app to learn more how to play with CoreData. I am now facing the issue when I am trying to save images. Whe… --- ## [Interactive widgets : // TODO 4: add a scaffold widget](https://forums.kodeco.com/t/interactive-widgets-todo-4-add-a-scaffold-widget/154996)
**Author:** [@olivaxa](https://forums.kodeco.com/u/olivaxa)\ **Replies:** 1\ **Last updated:** [October 27, 2021, 6:39pm UTC](https://forums.kodeco.com/t/interactive-widgets-todo-4-add-a-scaffold-widget/154996 "2021-10-27T18:39:23Z")
Hi. I didn’t find this TODO in the training. Maybe you should replace : @override Widget build(BuildContext context) { return const EmptyGroceryScreen(); } with @override Widget build(BuildContext conte… --- ## [How do I generate an augmented reality app without coding?](https://forums.kodeco.com/t/how-do-i-generate-an-augmented-reality-app-without-coding/154984)
**Author:** [@alice7890](https://forums.kodeco.com/u/alice7890)\ **Replies:** 0\ **Last updated:** [October 27, 2021, 5:32am UTC](https://forums.kodeco.com/t/how-do-i-generate-an-augmented-reality-app-without-coding/154984 "2021-10-27T05:32:37Z")
AR is amazing. You hold up your phone or tablet, point it at the world you know, and it changes right in front of you. PlugXR is a plugin that helps developers build AR apps and games for both iOS (ARKit) and Android (AR… --- ## [MDLMesh cylinder explanation of parameters of constructor](https://forums.kodeco.com/t/mdlmesh-cylinder-explanation-of-parameters-of-constructor/154897)
**Author:** [@andreiliphd](https://forums.kodeco.com/u/andreiliphd)\ **Replies:** 1\ **Last updated:** [October 27, 2021, 12:35am UTC](https://forums.kodeco.com/t/mdlmesh-cylinder-explanation-of-parameters-of-constructor/154897 "2021-10-27T00:35:01Z")
Hi I looked at the parameters for creating cylinder and it seems that I don’t understand some of them. init(cylinderWithExtent extent: vector\_float3, segments: vector\_uint2, inwardNormals: Bool, topCap: Bool, botto… --- ## [Do these lint rules automatically come with new flutter apps?](https://forums.kodeco.com/t/do-these-lint-rules-automatically-come-with-new-flutter-apps/154958)
**Author:** [@jefff9511](https://forums.kodeco.com/u/jefff9511)\ **Replies:** 1\ **Last updated:** [October 27, 2021, 12:29am UTC](https://forums.kodeco.com/t/do-these-lint-rules-automatically-come-with-new-flutter-apps/154958 "2021-10-27T00:29:22Z")
Are the lint rules we’re using standard for all new Flutter apps or would we want to get them from somewhere else? If we get them from somewhere else, how would we incorporate them? --- ## [When do you specify widget.property instead of class.property](https://forums.kodeco.com/t/when-do-you-specify-widget-property-instead-of-class-property/154945)
**Author:** [@jefff9511](https://forums.kodeco.com/u/jefff9511)\ **Replies:** 0\ **Last updated:** [October 26, 2021, 8:39pm UTC](https://forums.kodeco.com/t/when-do-you-specify-widget-property-instead-of-class-property/154945 "2021-10-26T20:39:37Z")
In 6.9, there is this code: final originalItem = widget.originalItem;. Why is it that instead of final originalItem = GroceryItemScreen.originalItem;? Doing it the latter way gives an error Instance member 'originalIte… --- ## [Chapter 6. Interactive Widgets](https://forums.kodeco.com/t/chapter-6-interactive-widgets/154647)
**Author:** [@ericsath](https://forums.kodeco.com/u/ericsath)\ **Replies:** 4\ **Last updated:** [October 26, 2021, 10:46am UTC](https://forums.kodeco.com/t/chapter-6-interactive-widgets/154647 "2021-10-26T10:46:51Z")
6.9 Creating the screen to add grocery items I’ve got issue in Scaffold AppBar, i have followed the example line of code but what i get is like this It should like this --- ## [ThemData(colorScheme: xxx) vs ThemeData.from(colorScheme: xxx)?](https://forums.kodeco.com/t/themdata-colorscheme-xxx-vs-themedata-from-colorscheme-xxx/153238)
**Author:** [@salmankhilji](https://forums.kodeco.com/u/salmankhilji)\ **Replies:** 2\ **Last updated:** [October 26, 2021, 5:17am UTC](https://forums.kodeco.com/t/themdata-colorscheme-xxx-vs-themedata-from-colorscheme-xxx/153238 "2021-10-26T05:17:01Z")
In Chapter 2, Hello, Flutter, Section, Styling your app, we theme our app like this: @override Widget build(BuildContext context) { final ThemeData theme = ThemeData(); return MaterialApp( title: 'Recipe Calcula… --- ## [Help with displaying a decimal number](https://forums.kodeco.com/t/help-with-displaying-a-decimal-number/154645)
**Author:** [@carlstep333](https://forums.kodeco.com/u/carlstep333)\ **Replies:** 10\ **Last updated:** [October 25, 2021, 5:17pm UTC](https://forums.kodeco.com/t/help-with-displaying-a-decimal-number/154645 "2021-10-25T17:17:25Z")
Hi, I’m working through the book and trying to apply what I’ve learnt creating the recipe app to my own ‘playground’ app. I’ve created a basic currency conversion app, the slider adjusts an input amount and the return g… --- ## [Chapter 32: Search Bar Height](https://forums.kodeco.com/t/chapter-32-search-bar-height/154755)
**Author:** [@sebaferreras](https://forums.kodeco.com/u/sebaferreras)\ **Replies:** 0\ **Last updated:** [October 25, 2021, 5:13pm UTC](https://forums.kodeco.com/t/chapter-32-search-bar-height/154755 "2021-10-25T17:13:13Z")
Hello! This is probably a very silly question but anyways… When selecting the search bar in the StoryBoard, the height shown is 51 points (this is also the value used when setting the tableView contentInset tableView.… --- ## [Creating custom design system similar to material by reusing the flutter/material as part of a package](https://forums.kodeco.com/t/creating-custom-design-system-similar-to-material-by-reusing-the-flutter-material-as-part-of-a-package/154719)
**Author:** [@msbasanth](https://forums.kodeco.com/u/msbasanth)\ **Replies:** 0\ **Last updated:** [October 25, 2021, 1:11pm UTC](https://forums.kodeco.com/t/creating-custom-design-system-similar-to-material-by-reusing-the-flutter-material-as-part-of-a-package/154719 "2021-10-25T13:11:18Z")
We are trying get very specific customization possibility than what material design provides by default. One approach of course is to create a design similar to flutter material. But creating entire design system from sc… [Previous page](https://forums.kodeco.com/c/books/6.md?page=37) [Next page](https://forums.kodeco.com/c/books/6.md?page=39)