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Learn the Basics
Component, the basic building block of the React UI. Components contain immutable properties, mutable state variables and expose a method for rendering.
Your current application is quite simple and only requires a render method. React Native components are not Android view classes; instead they are a lightweight equivalent. The framework takes care of transforming the tree of React components into the required native UI.
Then, get rid of the instructions assignment code block as you no longer need it. Save your changes to App. Then check Show All Proceses, select com.
Your text is being displayed in a view called ReactTextView: But what is that? Go to the project file finder and enter ReactTextView. Select the result matching this file to view the source code.
Make sure the app is still running, then return to your text editor to edit App. You can even skip having to refresh the app by enabling live reload.
Note that the emulator automatically refreshes to reflect your changes: Adding Navigation React Navigation is a community effort led by Facebook and Expo to provide an easy-to-use navigation solution for React Native apps. Save your changes and check the emulator to see the updated UI: Excellent — you now have the basic navigation structure in place.
Along with the style, you can very easily visualize the UI constructed by this component: a container with two text labels. Remove the SearchPage class and its associated description style from App.
Learn React Native
This may also be a good time to get rid of the all unused imports: those from react and react-native. React Native uses the Yoga library under the hood to drive layout. So far, your layout has a container with two children arranged vertically: This is due to the default flexDirection value of column being active.
Your app has set this value to center. This means the children are center-aligned. Open SearchPage. Yoga first lays out the text input and button according to their sizes. It then distributes the remaining space according to the flexGrow values. The text input therefore takes over the remaining space. Handling Assets The final step to complete the search screen of the application is to add the house graphic.
Download and unzip the images zip file.
Next, create a directory in your root project folder named Resources. Place the three images of the house in this directory. It also provides a single place for adding images if you are building for both iOS and Android. Back in SearchPage. Your task now is to add some state to your app and perform some actions. Adding Component State A React component can manage its internal state through an object called, you guessed it, state. Within SearchPage. This takes care of setting the initial state, but what happens when the user edits this text?
As a result you often see developers prefixing methods with an underscore to indicate that they should be considered private. You should see something like this: You call this. This triggers another render. You log the current and the next search text values. A React component state change triggers a UI update.
This de-couples the rendering logic from state changes affecting the UI. Most other UI frameworks put the onus on you to update the UI based on state changes. This is where React gets really smart.
Each time the UI renders itself, it takes the view tree returned by your render methods, and reconciles — or diffs — it with the current Android UI view. The output of this reconciliation process is a simple list of updates that React needs to apply to the current view.
That means only the things that have actually changed will re-render!
You can wrap your head around all that later; you still have some work to do in the app. In order to implement the search functionality you need to handle the Go button press, create a suitable API request, and provide a visual indication that a query is in progress.
This should kick off when the Go button is pressed. Similar to XML attributes, we pass in the props directly to a component and can then use the props inside the constructed component. Re-Render on Changes In addition to props, components can also have an internal state. The most prominent example of that behavior would be a click counter that updates its value when a button is pressed. The number of clicks itself would be saved in the state. Each of the prop and state change triggers a complete re-render of the component.
Virtual DOM Now when everything is re-rendered when the props or state changes, how come React itself is performing that well? The Virtual DOM consists of light representations of elements modeled after the component tree, making the process of generating them much more efficient than generating real DOM elements.
Before applying the changes to the real DOM, checks are done to determine where exactly in the component tree the changes happened, a diff is created, and only those specific changes are applied.
Getting Started with this React Native Tutorial There are certain prerequisites that beginners will need to set up in order to develop for React Native.
What helps is installing Watchman through the Brew package manager with brew install watchman. While this is not necessarily needed, it helps when dealing with a lot of files inside our React Native project. Tweet To install React Native, we simply need to install the React Native command-line application with npm install -g react-native-cli.
Calling the react-native command then helps us create a new React Native application. Running react-native init HelloWorld creates a folder called HelloWorld in which the boilerplate code can be found. We use some ES features in this code example, specifically classes. It is completely feasible to stick with React. Please click me. It is similar to the transition React developers had to go through when being confronted with JSX and previously using templating engines like Handlebars or Jade.
We declare the stylesheets directly at component level, and so we have all the information we need to see what our component does, the layout it creates, and the styles it applies.
There are different types of touchable components available, each of them providing a different visual feedback. Step 5: Customize Behavior Across Platforms It is possible to detect which platform the React Native application is running on, by accessing the value of Platform.
We can do it like this Step 6: Custom Fonts and react-native link In order to add a custom font, we need to jump through some hoops. After that, we need to create an assets folder and point npm to it.
Any other directory will do, but this is the conventional name used for the fonts directory. That will copy the fonts to the right directories and will add the necessary xml to info. Once done, we can use our font by just referencing it in any stylesheet by its full name. Those two properties control how the component is aligned respectively along its primary axis and its secondary axis. By default, the primary axis is the vertical one, and the secondary axis is the horizontal axis you can change that by setting the flexDirection property to row.
The first three behave like they do for justifyContent, while stretch will set the component to occupy all the available space along the axis, so that the axis will be completely filled.
Step 8: Registering the Application When developing with React for the browser, we just need to define a mount point, call React. In React Native, this is a little bit different.
React Native Tutorial in PDF
The name we give has to match with the name inside the Xcode project. Our Hello World React Native application has significantly more lines of code than its web counterpart, but on the other hand, React Native takes separation of concerns a bit further, especially because styles are defined with the component. It rebinds the method on every render call which can become quite a lot.
The alternative is to bind the method inside the constructor. Running the Application To run the application, we need to replace the contents of the index.
Then we just need to open the Xcode project and press the big Run button. First, a terminal will open with the React Native server, and then the simulator window will appear. The React Native server creates a bundle, which the native application will then fetch.
This allows for a web development-like rapid development cycle, where changes will be reflected almost instantly in the simulator. After the terminal has popped up, our application will then show up in the simulator. Clicking on the box will then show an alert.
Advanced iOS Summer Bundle
Let us start by saying that React Native is a relatively new technology. Thanks to people like you?