How frameworks generate code and add to class path - android

I apologies for my ignorance. Lately I have been working on Android framework. The developer said it is fastest framework built to the date because it does not uses reflection and generates code while building apps. I just want to know how these frameworks generate code and how they include this code in class path. What's there approach ? I want a general concept because I have few ideas and I want to implement them like this.

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Create custom SDK for React Native

What i want to achieve is something like creating my own SDK like what react-native-fbsdk or rn-onesignal-sdk provides , so that those functionalities can be implemented in the react native project.
Basic questions :
Where to start from? Like what are the pre-requisites?
Native coding is required i believe for this functionality?
Any explanation or any such experience in such would be of great help .
Where to start from? Like what are the pre-requisites?
You can use a template like this one. It includes an example project which is basically an app that you can use to test integration of your native module and to quickly iterate on it.
Native coding is required i believe for this functionality?
Only if you need to use platform-specific functionality, or provide bindings to some pre-existing native library. Both examples you mentioned do exactly that – because they have native SDKs that can be used in non-RN apps, and they provide React Native bindings for them.
If your library is just business logic + some networking, and you don't intend it to be used in non-RN apps, you can do it all in JS. No need for native code. If you choose to go with the template that I have linked above, there are instructions how to use it to create a pure JS React Native library.
I'll be happy to update my answer if you can share some concrete requirements of what you want your SDK to do.

Implement camera lib with Kotlin multiplatform

I'm trying to understand what structure should have a multiplatform library. Checking on the Internet I've seen a huge number of examples explaining how to make a log or a "hello world" but there's a lack of complex examples, even in the official documentation (important to note that I'm only interested in mobile platform, iOS and Android).
So I want to create an example that simply opens the camera (as a lib, not as a multiplatform app) just to have an idea of how to work with a real feature which, also, is native. Right now I have created a project following the official example, so it has a common module (using expect) and one for Android and one for iOS (using actual), and now these are my doubts:
I've seen that the iOS module is also in Kotlin, Kotlin/Native as I understand. Should my project have also an wrapper in Swift, or will the library have no Swift code? And if it should, where should it be in the project structure?
Also in the Android module I've noticed I cannot import the class "Activity" nor the "Intent", which I will need to open the camera, why? is this code restricted to Java without the Android libs? Should it also have a wrapper to Android? If so, how can I configure this wrappers?
I know I can use the "expect" key when creating classes but, as I understand, the common and the native modules will always be separated classes. I mean, if I create a class in the common module, can I define methods of this class using "expect" and define them later in the native?
Can my lib have a Manifest?
Finally, does anyone knows a real example that really explain a more complex situation?
Thanks
Okay, let's go through your questions one-by-one.
I would recommend you to have a look at this example
The
iOS module produces an Objective-C framework as a result. It can be utilized by the Xcode project the same way as any other framework with non-Kotlin origins.
It looks like the unavailability to use
Android SDK is the result of using jvm("android") target instead
of android() one. To use the android target, one has to apply the android Gradle plugin in addition to kotlin-multiplatform one.
I
think you want to do something like that: just ordinary class
declaration in the common and extension function for it with an
expect modifier. And then actualize it in the platform-specific
code.
I think so.
I'd also recommend you to have a look at
this and this, maybe these examples will be complex enough for you.😁

How are your experiences with NativeScript?

Does anyone have experience with NativeScript and can compare it to developing native apps, especially for Android?
I have read all these articles:
FIRST THOUGHTS ON NATIVESCRIPT
SECOND THOUGHTS ON NATIVESCRIPT
Introduction to Native Script – Is It Worth Your Time?
My Experience Developing with Telerik NativeScript
I know especially three of them may be outdated. But I want to ask all of you developers:
How is your experience with NativeScript?
Are there any Android-Components you cannot use? Which are these ones?
Is styling really so limited?
Do apps really look so different at runtime as in the mockup as in the pictures of the first article referenced above?
Does loading of native Android objects into JavaScript Code always work correctly?
Does NativeScript generate Java-Code for Android-Platform out of the NativeScript code I write?
Is it possible to modifiy this code if I want to use some native-only features? What if I want to make UI changes then? Do I have to regenerate the code and do I miss my native extensions then?
Very glad to see that you are evaluating NativeScript to eventually use it in present and future projects.
I'll try to condense answers to a few of the questions into one, as they really are mostly related.
Skipped.*
That depends on what has already been exposed through a custom view/plugin or module. The core-modules that every NativeScript app comes with contains the most basic of wrappers for both Android and iOS under a common API. There are plugins (nativescript npm modules) that provide additional wrappers on native android views (nativescript-telerik-ui for one, nativescript-carousel), most of which are created by the NS community.
As RexSplode mentioned before me - it's mostly the platform that imposes certain limitations. NS uses CSS to declare style, but you can also access the native components and manage their style and appearance programatically if what you need isn't readily available out of the box.
First I'd like to note that the first 3 articles you've linked are over a year old now, and trust me, NativeScript has evolved a lot since then. With all the available components (remember the npm modules I mentioned earlier?) there's a good chance that you will get a close to 1:1 similarity to a well-styled native Android mockup.
At build time metadata is generated for the Android/Java public API used in the project. When the JavaScript Engine (V8) fires up, that metadata is loaded into memory, prototype chains are constructed, and callbacks are attached, so that when you call new android.widget.Button(); in your JavaScript code, the proper virtual machine instructions will be called, and a native button will be created. Static methods are accessed similarly, check out the official docs to get a better understanding of how it all works.https://docs.nativescript.org/runtimes/android/advanced-topics/execution-flow
and 7., and a cont. of 2. Java code, or rather compiled Java code is generated whenever you wish to extend a native Android class that isn't available already in a module or in the native Framework. Extending classes is very similar to how you would do it in Java - you extend a class, and create new implementations of interfaces. That means that you won't have to open Android Studio to create a new class, build it into a native plugin and then add it to your project, since you can do it all in your NativeScript code using JavaScript/TypeScript. https://docs.nativescript.org/runtimes/android/generator/extend-class-interface
Disclaimer: I am on the NativeScript Engineering team
I investigated the Native Script a little and my colleague at work writes an app with it, so I can offer you a bit of information that I have.
1. skipped
There are limited amount of components you can use with native script out of the box. However, if you have a native-java developer who can write a wrapper for you - you can use everything.
It is limited to the platform you are using. Android itself has a lot of style limitations which cannot be easily overwhelmed.
don't know
It works a little different. Your JS object, or rather widgets are translated to java code. So with the items from the box - yes, they are okey. If you write a wrapper for your custom component, then all is up to you.
Yes it does.
No, the code is generated, how are you going to modify it? Changes will be undone on the next build. However, you can write a native module for your application and use any features you want. It is like defining an interface, which you can use in JS code afterwards.

Code injection for Android

I want to write an ORM for Android as my final project.
My first idea is to inject code for each get and set.
Unfortunately I found a lot of posts saying there is no way to inject code in Android.
On the other hand I found "Dexmaker" to generate code on runtime.
My question is: Is it possible to somehow inject code in Android (by "Dexmaker" or anything else)?
If not how to do it ?
I also thought about reflections but I am afraid that it will be to slow.
Thanks in advance.
Edit
Simon:
Yes by ORM I ment object relational mapping.
I want to create a general framework. How else I could do this than not by code injection ?
You can inject code using Dexmaker. The project site has a HelloWorldMaker example that generates a class and then loads it.
You may find the performance of runtime code generation to be unsatisfying however. Projects like Dagger have had better success metaprogramming with code generation.

C++ File adding

Can anyone please tell me how to add a C++ file in to an android project? Is there any method to import classes other than java classes?
The answer is that, you can't really add a C++ file directly to a project, but you can compile it and load it into the code that runs in your process and interface to it using the JNI. This is a way to interface native code to Java. However, be aware that you can't really do that much with the JNI. Getting access to standard Android things like UI, Intents, service connections, etc.., these are all somewhat more difficult to use in native code. And you certainly can't take a UNIX app "off the shelf" and stick it on Android by using the JNI. this is a fairly good looking tutorial on the JNI with Android. However, like I said, using the JNI is not an excuse for learning java and the Android SDK. The main reasons people use native code are for utility code (like crypto stuff) and performance (for example, quite a few Android games use the NDK)..
You have to use android NDK. Just download it and refer from android official site.

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