Learn Android, Chai and Edge

Open source framework for building truly native mobile apps with Angular, TypeScript or JavaScript.

nativescript

We will learn how to add an Android library to our project and translate it’s Java api to NativeScript. For this lesson, we will look at [Filestack’s Android SDK](https://github.com/filestack/filepicker-android) built with Gradle. Specifically, we will cover how to immediately start working with the library even when a [NativeScript](/q/nativescript) plugin does not exist for it.

Use an Android library in NativeScript for Angular using Java apis

Java has been around a long time and when it comes to Android, you will encounter some structures that may throw you for a loop on how to code against with NativeScript. Let’s examine a few common Java/Android api constructs you may encounter and how to translate them to NativeScript. Learn how to get references to local files in your app using the ‘file-system’ module as well as how to take advantage of NativeScript’s Observable class to send notification events from one class to another. Lastly, look at considerations with Angular’s NgZone when handling your native libraries data events to update component view bindings.

Translate common Java/Android APIs into NativeScript for Angular Android apps

One of the exciting benefits you have with NativeScript is the ability to write native code (Java and Objective C) directly in JavaScript/TypeScript allowing you to create a consistent high level api over top of both underlying iOS Objective C/Swift and Android Java apis. In this lesson, we will look at how to design a consistent api that taps into the appropriate native api’s on the target platforms using underlying native libraries.

Develop a consistent plugin api across your Android and iOS NativeScript app

To prepare your development environment to code against native apis such as Objective C, Swift and Java, let's learn how to [install tns-platform-declarations](https://www.npmjs.com/package/tns-platform-declarations) to provide rich intellisense support for all the native iOS and Android api’s. This lesson will cover how to modify your tsconfig.json and references.d.ts properly to ensure working with native api’s is smooth and as helpful as possible.

Prepare for native iOS and Android api intellisense with NativeScript

Building a custom NativeScript XML view component for Android is uniquely different than it’s iOS counterpart because of the Android Context which must be considered. Let’s look at how to properly build a custom view component based on an underlying native view widget. We will also look at what happens when our include.gradle file is not setup properly including handling problems with minimum sdk targets with plugins. Specifically, we will implement this Android widget representing the [Google I/O 2016 clock](https://github.com/lypeer/GoogleClock). Learn how to create a custom AndroidManifest.xml inside your plugin to merge with your app's manifest to override certain characteristics. Read detailed documentation about the [Android app manifest file](https://developer.android.com/guide/topics/manifest/manifest-intro.html).

Build a custom NativeScript view component for Android

edge

Coding for accessibility? You should get familiar with the accessibility tree, a structure produced by platform Accessibility APIs running parallel to the DOM, which exposes accessibility information to assistive technologies such as screen readers. There are multiple tools for visualizing this tree; in this lesson we'll look at Chrome and Microsoft Edge. For more on Accessibility APIs, refer to this [amazing article by Leonie Watson](https://www.smashingmagazine.com/2015/03/web-accessibility-with-accessibility-api/). For a how-to on setting up the Chrome Accessibility Inspector, visit [bit.ly/chrome-a11y](http://bit.ly/chrome-a11y).

What is the Accessibility Tree?

Chai is a BDD / TDD assertion library for node and the browser that can be delightfully paired with any javascript testing framework.

chai

Every dependable library needs to have tests to ensure that you don't push accidental bugs. In this lesson, see how you can set up mocha and chai to start testing your library.

Setting up Unit Testing with Mocha and Chai

Now that you've got everything set up with mocha and chai, it's time to actually write tests. In this lesson you'll learn how to use `describe` and `it` to outline your tests and make sure you don't break your library in the future.

Unit Testing with Mocha and Chai

In this lesson, we will use Chai's request method to test our Node application's API responses.
By the end of this lesson, you will know how to:
- install the prerequisites to use mocha and chai in your application
- test for HTTP status response codes
- test for a string of text on a page
- test for a json response and validate the properties of the object
- write tests that not only verify the response of your application, but the behavior as well


Test Node RESTful API with Mocha and Chai

Mocha is a feature-rich JavaScript test framework running on Node.js and in the browser, making asynchronous testing simple and fun. Mocha tests run serially, allowing for flexible and accurate reporting, while mapping uncaught exceptions to the correct test cases.

mocha

Writing great ES6 style Promises for Node.js is only half the battle. Your great modules must include tests as well to ensure future iterations don't break them. In this lesson, I show you a simple ES6 Promise in Node.js, then walk you through creating tests in Mocha using chai and chai-as-promised to test both resolve and reject methods.

Testing ES6 Promises in Node.js using Mocha and Chai

React Native lets you build mobile apps using only JavaScript. It uses the same design as React, letting you compose a rich mobile UI from declarative components.

react-native

Learn to write components that render differently on iOS and Android, but present the same API. First, we'll use the Platform module to change behavior based on the platform. Then, we'll use the platform-specific file extensions, .ios.js and .android.js, to render platform-specific components.


Writing Platform-Specific Components for iOS and Android in React Native

In this lesson, you will learn how to verify your API server is returning HTTP 400 responses when clients submit incorrect data. Returning HTTP 400 ensures that your clients are notified of the incorrect usage. Testing for them ensures your API returns errors instead of incorrect responses when supplied with incorrect data.

Test for HTTP 400 responses with Mocha and Chai

In this lesson, we will start with a list of content from a React Native FlatList that we will then transform into a three-per-row grid.

Display Contents of a React Native FlatList as a Grid

In this lesson, you will learn how to use the `SafeAreaView` component to avoid the sensor cluster (the notch) and home activity indicator on the iPhone X.

Use the SafeAreaView Component in React Native for iPhone X Compatibility

First, install redux with: `npm install --save redux` and install react-redux with: `npm install --save react-redux`

In the top level of your component tree, import `createStore` from redux, and use it to create a new store with a simple reducer:

`import { createStore } from 'redux'`

`const rootReducer = (state = {}, action) => {
  return state
}`

`const store = createStore(rootReducer)`

Also import `Provider` from react-redux:

`import { Provider } from 'react-redux'`

And then wrap your app's components with a `Provider` component, and pass in your `store` as a prop:

`<Provider store={store}>`
  `...`
`</Provider>`

Then, you can connect any sub components with the `connect` function, by first importing it:

`import { connect } from 'react-redux'`

And then calling it with a `mapStateToProps` or `mapDispatchToProps` argument, and then passing in the unconnected component:

`const ConnectedLoginGate = connect(state => ({
  username: state.auth.username
}))(LoginGate)`





Add Redux to an Existing React Native Application

ASP.NET is an open source web framework for building modern web apps and services with .NET. ASP.NET creates websites based on HTML5, CSS, and JavaScript that are simple, fast, and can scale to millions of users.

asp-net

If you want to improve a REST API beyond GET/POST&PUT and DELETE the next step would be adding the push functionality to send new data into your web applications. With ASP.NET Core and SignalR you can add this functionality with ease and keep your application up to date without letting the clients reloading their page manually.

[signalr npm](https://www.npmjs.com/package/@aspnet/signalr), [signalr Core](https://www.nuget.org/packages/Microsoft.AspNetCore.SignalR.Core/)

[archived] Expose Values for Real-time Consumption with SignalR in ASP.NET Core

iOS and Android come with several built in fonts, but if you want to use a custom font in your react native application, you'll need to add it first.

You can add a custom font by copying the font files to your project, telling react native where to find those files by adding an `rnpm` entry to your `package.json` file, and then linking them with `react-native link`. 

Then, you can use that new font by specify it as the `fontFamily` style for a `Text` component, and you can change the `fontWeight` or `fontStyle` component if you've added additional style and weight font files.



Add a Custom Font to a React Native Application

There are two ways to open urls in React Native.  One is to open, and switch to the device's web browser, and the other is to embed the web page within your application.

To open the mobile device's web browser, we'll import `Linking` from react native, and use the `openURL` function, which will open any url that starts with `http` or `https` in that web browser.

If you want to stay within your current application however,  you can import `WebView` from react native, and use that as a component in your application.  Pass in a `uri` param to display that web page in the embedded web view.

Open a Webpage in React Native with Linking and WebView

When you bring up the on screen keyboard in a mobile app, it will cover any text input or buttons on the bottom half of the screen, which can be frustrating for users.  There are a few common ways to deal with this in React Native - and this video shows the following solutions:

First, you can use the built in `KeyboardAvoidingView` to move components around when the keyboard comes on screen.  It has the advantage to being built in to React Native already - but it can be overly complicated to get this approach to work consistently across both iOS and Android.

There is also a third party library called `KeyboardAwareScrollView`, which will allow your entire view to scroll, and will keep the currently selected text inputs up and out of the way of the keyboard.

Prevent the On-screen Keyboard from Covering up Text Inputs

We’ll create a brand new React Native app, and get it to launch on the iOS simulator and Android emulator.  A Mac is required to build for iOS, but Android development can be done on Mac, Windows, or Linux.

Create a React Native App and Run it on the iOS Simulator and Android Emulator

Once your React Native app is up and running, we’ll make a simple change and reload the simulator to show the change.  We’ll look at manually reloading the simulator, reloading with Live Reload and reloading with Hot Reloading, and talk about the pros and cons of each method.

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