Develop Reference

How to use mediapipe graphs like the mediapipe API-s

I'm struggling to understand how am I meant to interact with the "graph" and "calculator" stuff from the mediapipe library. More specifically, I'd like to write some Android code that uses landmarks from the holistic (pose + hands in my case) solution, with the final goal of writing a flutter application that compiles both for Android and iOS.
I've managed to build a few of the sample apps (thanks to docker), and I think I roughly understand what the graphs do. However, I don't understand how to interact with them from within the code. The Hello World! for Android tutorial doesn't really explain this. There are examples that include this type of behaviour (e.g. here), but I don't really know where is all the required information coming from (e.g. how would I find out the right functions and string constants to get holistic landmarks?)
For example, in Python I could get data via something like holistic.process(image).pose_landmarks, and then compute e.g. position or angle of hips. And as far as I can see there are some similar Android API-s available, although not for all solutions - including holistic. So what if I don't want to wait for the API-s development, and want to use the graphs instead? That part is not so clear.
As a bonus, please do feel free to drop any links which further explain/document the "graph" and "calculator" stuff I've mentioned earlier, as I've not used anything like this before and find it a little difficult to google.
Thanks.

I've realised there are docs available: https://google.github.io/mediapipe/framework_concepts/framework_concepts.html
Not sure how I've missed this...

Starting point for app creating, where to start

I am looking to start writing apps for mobile devices. I know a little about this subjec, and I am proficient in both java and python. However, before jumping into creating apps I wanted to get the community's input on a question I have not yet found the answer to:
How/Where should I begin?
I understand this question is fairly general/basic for a community that focuses on solving/debugging complex programs, but if there is a recommended tutorial (or specific platform) that will help a beginner(such as myself), it would greatly reduce the frustration and amount of monotonous questions asked on this forum and others.
Regards

Coursera is offering 3 courses all using android development which started last week. That would be an excellent starting point for anyone:
https://www.coursera.org/specialization/mobilecloudcomputing/2

How/Where should I begin?
I don't know about you, but I often learn by example more than reading. You mentioned that you're proficient in java so thats a great start. After you understand the Android SDK it's really only the UI good practices you need to learn. So here's my suggestion.
Start off with something super simple. Let's say, create your own version of a calculator. Something that can add, subtract, multiply, and divide. This should be dirty, ugly, but works correctly.
After doing this, take a look at some other android calculators on the play store. Check out Simple Loan Calculator. I use this example because it offers a lot of android UI components. ViewPager, ActionBar, etc. Download this app, take a look at it, and try to mimic it. This should provide an idea on how to work with the android UI components.
What's next? After you have done these two apps you should be relatively ready to tackle your own project.

HTML apps are easy to port across multiple mobile platforms. I have set up an Android HTML template as a starting point. You can just import this project into Eclipse and take a look at that.
https://github.com/jakewp11/HTML5_Android_Template

Here is my experience for ios,
There are three things that I consider as pillars
Objective C
Memory managment
Design patterns
The first one looks obvious but I'd stress on learning concepts like protocols, categories, extensions. As a beginner I thought that learning the syntax was enough, but time and again I had to jump back to the language concepts to understand what's going.
The memory managment , the most talked and confusing subject and now since we have automatic referenc counting to make things simpler and often new Dev skips learning memory concepts (I did it). So I suggest you to have an idea what actually happens under the hood of arc " the manual memory managment"
The design patters,
When I started off , to pass data and control , what I used to do was achieve every thing through the only design patten I knew (target action) . I lack the knowledge of design patters didn't how easily I could achive better results with less code.
Some resources:
Dev.apple.com
http://www.raywenderlich.com (one of my best tutorials are here, you can find one on design patterns)
http://rypress.com/tutorials/objective-c/
And yes , the sample projects at Dev.apple are the best tutors.

jQquery Mobile site project for categorised notes - sanity check please?

I am asking for your advice and a sanity check, please. For a couple of years I have thought about building a mobile site for my own purposes (initially) that will allow me consistent interface on the web and on a mobile phone. My initial target is Android 4 and above.
The central idea is to make notes via web interface. It is easy to
edit on a full PC. Basic formatting is necessary - bold, italic,
lists. I should have some basic editing / adding capability from the phone.
Possibly I might need to add images. This at a later stage.
I will need to use tables.
View these categorised notes on my phone when I need to access that information quickly.
Information should be searchable.
I should be able to categorise that information both hierarchically and by labels.
On the phone the last copy of the information should be available even when there is no internet access. That is the key bit of this project - clear, well structured information, easily available when needed.
So far I have done some 7 websites 6 - 9 years ago and this year I did a responsive design interface with jQuery and HTML5. I have access to Apache on a linux hosting site. I have looked into jQuery Mobile. I think jQuery mobile should be great for my front-end. From my past work with LAMP servers I think I have to have a database backend to this project. What I have looked into so far suggests that the best would be to invest some time in learning Ruby on Rails (which looks very interesting to me) and use that as a back end interface with a database. What database I should use, I don't know. I have in the past used mySQL, also programmed Access and a bit DB2. I have heard a lot of good stuff about postgres. However considering the mobile phone, I think I should go with SQLite probably? What should be the general mechanism for updating the phone from the net?
How does the above look?
Maybe there are some projects which already do something like this?
I don't think I should use some big CMS systems with their bloat and all, because I really want this thing to work for me. Same goes for generic note taking systems such as Evernote. So I am wanting to build it from the ground up, unless there is some similar lightweight project that I could build upon. I am not in a particular hurry, but I am about to get started soon.
A great type of answer for me would be one which tells what major components I should use for this project. It also would be good to know if I am overlooking some important bits.
I appreciate that what I am asking is a large question, but I am not expecting a Wikipedia in response. A sanity check and pointers in the right direction is what I need.
Thank you for your time and thoughts.

What a wall of text... 1.-7. are all achievable by using jquery mobile and HTML5 and a good database architecture as backend. I don't see any BIG problems in your idea. What database you use is up to you, your requirements are not that special, that it would require some specialized product. Any established database backend should do the job.
For updating the content on your phone take a look on HTML Offline Cache and implement an update feature in your Frontend.

How to use webservices in android?

I want to know about how to call webservices in android I had done a lot of search from Internet and have read several tutorials but was not able to understand much and manipulate, can anyone suggest any Tutorial, or provide any Pdf file or any book related to web services so that I can understand it.
Thanks in advance

The first reading I would suggest is this one - this is the W3School tutorial. Don't forget to read the related chapters included in this tutorial - Soap, Wsdl, etc - as this tutorial taken as a standalone would not be so valuable. This tutorial is not specifically related to Android but will give you all the information needed to understand the use and constraints of this kind of architecture, and then structure your project.
Under Android, you will face the specific contraint of mobile phones and tablets: the network can be down, and is often down: in the tube, in a basement, in any area that have a bad network coverage. So you will have to take care of this, either by caching data or allowing the application to work in degraded mode when no network is available. These are just examples as I don't know your context.
After that, Android is developed in Java, with a specific API that comes on top of the regular java.* packages. These are just tools to implement the client side. On server side, depending of whether you control these services, you may also have some implementation to do. If so, this can be Java, PHP, .Net, anything: one of the purpose of the web services architecture is to stay independant of the remote implementation to only care the exchange protocol. But reading your question, I think the two first points are more important (or have an higher priority let's say) than the implementation as they are prerequisites. (EDIT: Anyway, a useful discussion about that can be found here on StackOverflow.)

Android Doesn't have it's own tool then you should use your own or use some Thing Like KSOAP2.
You Can Use This.
http://www.c-sharpcorner.com/UploadFile/88b6e5/how-to-call-web-service-in-android-using-soap

Where to find Android Development Homework Problems

Ok so I am starting off with android development and I have found a bunch of useful tutorials so I am set there. What I am looking for is a resource that provides homework style problems to do and has the answers downloadable so I can check my solution against the "official" solution.
So for example instead of the notepad tutorial it would be: "Build an application that you can create, edit, delete notes, ...etc.". Ideally the "official" solution would have some explanation as to why they built it the way they did. (so a tutorial at the tail end)
Anyone know of any resources that provide their tutorials in this format?
Thanks.

Okay, here's one: build me an app that allows the user to make, modify, and store notes. The 'official' answer is the Notepad app in the 9th level of the api. (Note that this is different from the notepad tutorial).
The point is that asking questions is easy, the harder part is actually making a program that does the job. And #Roflecoptr is right, at this level it can be implemented very differently. But if you want that mindset, you can write your own 'homework' easily. Just think up a few things you want that are simple, build it, does it do what you want well? Then you pass.

Despite for very trivial problems I dont think this is possible, because there are way to much possible implementation possibilites so that you can't compare your solution to the "official" solution.
But why do you need something like that? If you want to learn to program on Android, you can just follow some tutorials you've already found and then modify them, adapt them to your needs. When you get more used to the development of Android apps you can just get some ideas on tutorials/android development sites and then implement your own solution. There is plenty of help available here on SO and on other development sites, which will help you if you really get stuck.

You could always go to the Android Samples page, and without looking at their implementations, do your own and compare. The samples page is here:
http://developer.android.com/resources/samples/index.html