How Much Does It Cost To Build A Carpooling App Like BlaBlaCar?

<img src="https://moriohcdn.b-cdn.net/904d9e5300.png">

Taxi booking app such as UBER, Lyft, and sidecar, etc. are popular in these days. The user just takes their smartphone out of their pocket and easily book their ride. It is one of the best things about this digital era. BlaBlaCar is a France based travel company which is used to share and take a ride for long distance or between cities.

Build an iOS and Android App using React Native

Build an iOS and Android App using React Native

A comprehensive step by step tutorial on building Android and iOS App from scratch using React Native. Build an iOS and Android app in 15 minutes using React Native. Create native apps for Android and iOS using React. React Native combines the best parts of native development with React, a best-in-class JavaScript library for building user interfaces.

Build an iOS and Android app in 15 minutes using React Native

A comprehensive step by step tutorial on building Android and iOS App from scratch using React Native.

React Native Tutorial - Build Android and iOS App from Scratch

React Native Tutorial - Build Android and iOS App from Scratch

React Native Tutorial - Build Android and iOS App from Scratch. Getting started tutorial on building an Android and iOS app from scratch using React Native. React Native is a modern Javascript framework backed by Facebook that use to make Mobile Apps (Android/iOS) development easier for Javascript developer. In other words, React Native is React.js mobile apps development version.

A comprehensive step by step tutorial on building Android and iOS app from scratch using React Native

A comprehensive getting started tutorial on building an Android and iOS app from scratch using React Native. React Native is a modern Javascript framework backed by Facebook that use to make Mobile Apps (Android/iOS) development easier for Javascript developer. In other words, React Native is React.js mobile apps development version. For more information about React Native definition, features, etc, you can find in their official documentation.

Shortcut to the steps:

  • Install React App Creator and Create A React Native App
  • Add Navigation Header and Home Screen
  • Load World Cup 2018 Data from API
  • Display List of World Cup Matchdays
  • Display World Cup 2018 Matchdays Details
  • Run the React Native World Cup 2018 App

In this React Native tutorial, we are creating an app that listing the World Cup 2018 matches using the free open public domain football data for the world cups in the JSON format.

The following tools, frameworks, and modules are required for this tutorial:

  • React Native
  • Node.js (NPM or Yarn)
  • Worldcup JSON data
  • Android Studio or SDK for Android
  • XCode for iOS
  • Terminal (OSX/Linux) or Command Line (Windows)
  • Text Editor or IDE (We are using Atom)

Before start to the main steps, make sure that you have installed Node.js and can run npm in the terminal or command line. To check existing or installed Node.js environment open the terminal/command line then type this command.

node -v
v8.11.1
npm -v
6.1.0
yarn -v
1.7.0

That's the Node and NPM or YARN version that we are using. In this tutorial, we will use Yarn commonly.

Install React App Creator and Create A React Native App

The Create React Native App is a tool for creating a React Native App. To install it, type this command in your App projects folder.

sudo npm install -g create-react-native-app

Then create a React Native App using this command.

create-react-native-app reactWorldCupApp

That command will create a React Native app then install all required modules. The app or project folder will contain these folders and files.

Next, go to the newly created React App folder.

cd reactWorldCupApp

This React Native App is running via Expo app, before running on your Android or iOS device, make sure you have to install the Expo App to Android or Expo Client to iOS. Of course, that app is available in the App Store. So, we assume that you have installed the Expo App in your device then type this command to run the app.

npm start

or

yarn start

You will see this barcode and instruction in the terminal or command line.

To open the app in the Android device, open the Expo App first then tap on Scan QR Code button. Scan the barcode in the terminal or command line then you will see the React Native Android App like this after waiting for minutes the build process.

For iOS Device, press s from the keyboard to send React Native App URL to your Email or SMS. Enter your phone number or Email address (We use an email address) then press Enter. You will get this email to your mailbox.

Choose open in Expo URL then open in your browser, that will be redirected to Expo App. In Expo App welcome screen, shake your phone to open the React Native App. Now, you will see this screen in your iOS device.

This step for development purpose, we will show you how to build for production at the end of this article.

Add Navigation Header and Home Screen

Above generated React Native App just show blank app with plain text. Now, we will show you how to add the Navigation Header and Home Screen for your app. So, it will look like the Native App. In the terminal or command line type this command to install React Navigation (react-navigation) module.

yarn add react-navigation

Next, create a folder for components and React Native components files in the root of the app folder.

mkdir components
touch components/HomeScreen.js
touch components/DetailsScreen.js

Open and edit components/HomeScreen.js then add this React Native codes.

import React, { Component } from 'react';
import { Button, View, Text } from 'react-native';

class HomeScreen extends Component {
  static navigationOptions = {
    title: 'Home',
  };
  render() {
    return (
      <View style={{ flex: 1, alignItems: 'center', justifyContent: 'center' }}>
        <Text>Home Screen</Text>
        <Button
          title="Go to Details"
          onPress={() => this.props.navigation.navigate('Details')}
        />
      </View>
    );
  }
}

export default HomeScreen;

Open and edit components/DetailsScreen.js then add this React Native codes.

import React, { Component } from 'react';
import { Button, View, Text } from 'react-native';

class DetailsScreen extends Component {
  static navigationOptions = {
    title: 'Details',
  };
  render() {
    return (
      <View style={{ flex: 1, alignItems: 'center', justifyContent: 'center' }}>
        <Text>Details Screen</Text>
        <Button
          title="Go to Details... again"
          onPress={() => this.props.navigation.push('Details')}
        />
        <Button
          title="Go to Home"
          onPress={() => this.props.navigation.navigate('Home')}
        />
        <Button
          title="Go back"
          onPress={() => this.props.navigation.goBack()}
        />
      </View>
    );
  }
}

export default DetailsScreen;

Next, open and edit App.js then add replace all codes with this.

import React from 'react';
import { StyleSheet, Text, View } from 'react-native';
import { createStackNavigator } from 'react-navigation';
import HomeScreen from './components/HomeScreen';
import DetailsScreen from './components/DetailsScreen';

const RootStack = createStackNavigator(
  {
    Home: HomeScreen,
    Details: DetailsScreen,
  },
  {
    initialRouteName: 'Home',
    navigationOptions: {
      headerStyle: {
        backgroundColor: '#f4511e',
      },
      headerTintColor: '#fff',
      headerTitleStyle: {
        fontWeight: 'bold',
      },
    },
  },
);

export default class App extends React.Component {
  render() {
    return <RootStack />;
  }
}

When the files are saved, the Expo app will refresh the React Native App automatically. Now, the app will look like this.

Load World Cup 2018 Data from API

To load World Cup 2018 data from API, open and edit components/HomeScreen.js then add constructor function before rendering function.

constructor(props){
  super(props);
  this.state ={ isLoading: true}
}

Add function for load API JSON data which the JSON response set to the dataSource.

componentDidMount(){
  return fetch('https://raw.githubusercontent.com/openfootball/world-cup.json/master/2018/worldcup.json')
    .then((response) => response.json())
    .then((responseJson) => {
      // console.log(responseJson);
      this.setState({
        isLoading: false,
        dataSource: responseJson.rounds,
      }, function(){

      });

    })
    .catch((error) =>{
      console.error(error);
    });
}

The response from API holds by dataSource variable that will use in the view in the next step.

Display List of World Cup Matchdays

We will use the List and ListItem component of React Native Elements (react-native-elements) module. First, install react-native-elements using this command.

yarn add react-native-elements

Open and edit again components/HomeScreen.js then replace all imports with these imports of React, Component (react), StyleSheet, ScrollView, ActivityIndicator, Text, View (react-native), List, and ListItem (react-native-elements).

import React, { Component } from 'react';
import { StyleSheet, ScrollView, ActivityIndicator, Text, View  } from 'react-native';
import { List, ListItem } from 'react-native-elements';

Next, replace all render function with this React Native rendered template which the ActivityIndicator load only if the state status is loading. The list that gets from the data source displaying to the ListItem after mapping the array of the data source.

render() {
  if(this.state.isLoading){
    return(
      <View style={styles.activity}>
        <ActivityIndicator/>
      </View>
    )
  }

  return(
    <ScrollView style={styles.container}>
      <List>
        {
          this.state.dataSource.map((item, i) => (
            <ListItem
              key={i}
              title={item.name}
              leftIcon={{name: 'soccer-ball-o', type: 'font-awesome'}}
              onPress={() => {
                this.props.navigation.navigate('Details', {
                  matches: `${JSON.stringify(item.matches)}`,
                });
              }}
            />
          ))
        }
      </List>
    </ScrollView>
  );
}

Add style const before the export code.

const styles = StyleSheet.create({
  container: {
   flex: 1,
   paddingBottom: 22
  },
  item: {
    padding: 10,
    fontSize: 18,
    height: 44,
  },
  activity: {
    flex: 1,
    padding: 20,
  }
})
Display World Cup 2018 Matchdays Details

We will display World Cup 2018 Matchdays Details in the DetailsScreen. Open and edit components/DetailsScreen.js then replace all imports with this.

import React, { Component } from 'react';
import { StyleSheet, ScrollView, View } from 'react-native';
import { List, ListItem, Text, Card } from 'react-native-elements';

Next, replace all render function with these lines codes.

render() {
  const { navigation } = this.props;
  const matches = JSON.parse(navigation.getParam('matches', 'No matches found'));
  console.log(matches);

  return (
    <ScrollView>
      <Card style={styles.container}>
        {
          matches.map((item, key) => (
            <View key={key} style={styles.subContainer}>
              if(item.group) {
                <View>
                  <Text h3>{item.group}</Text>
                </View>
              }
              <View>
                <Text h3>{item.team1.name} vs {item.team2.name}</Text>
              </View>
              <View>
                <Text h5>{item.date}</Text>
              </View>
              <View>
                <Text h4>{item.score1} - {item.score2}</Text>
              </View>
              if(item.goals1.length > 0) {
                item.goals1.map((item2, key2) => (
                  <View key={key2}>
                    <Text h4>{item2.name} ({item2.minute})</Text>
                  </View>
                ))
              }
              if(item.goals2.length > 0) {
                item.goals2.map((item3, key3) => (
                  <View key={key3}>
                    <Text h5>{item3.name} ({item3.minute})</Text>
                  </View>
                ))
              }
            </View>
          ))
        }
      </Card>
    </ScrollView>
  );
}

Add StyleSheet const before the export code.

const styles = StyleSheet.create({
  container: {
    flex: 1,
    padding: 20
  },
  subContainer: {
    flex: 1,
    paddingBottom: 20,
    borderBottomWidth: 2,
    borderBottomColor: '#CCCCCC',
  }
})
Run the React Native World Cup 2018 App

To run the application in Expo App, you can find in step 1 of this article. If there's no error found, you will see the result like this.


Next, to run or build as the Native App, type this command to install React Native CLI first.

sudo npm install -g react-native-cli

Next, eject the project from the Create React Native App by type this command.

npm run eject

You will get questions like below, make it the same with the one that we choose.

? How would you like to eject from create-react-native-app? React Native: I'd like a regular React Native project.
We have a couple of questions to ask you about how you'd like to name your app:
? What should your app appear as on a user's home screen? React World Cup
? What should your Android Studio and Xcode projects be called? ReactWorldCupApp

Next, to run the Native iOS or Android App in the Simulator, type this command.

react-native run-ios
react-native run-android

That it's for now. Any suggestions are open for next React Native tutorial. You can find the full working source code in our GitHub.

Introduction to Flutter: Building iOS and Android Apps from a Single Codebase

Introduction to Flutter: Building iOS and Android Apps from a Single Codebase

Flutter allows developers to develop both Android and iOS apps using a single codebase. In this tutorial, we will introduce Flutter by building iOS and Android Apps from a Single Codebase.

Flutter allows developers to develop both Android and iOS apps using a single codebase. In this tutorial, we will introduce Flutter by building iOS and Android Apps from a Single Codebase.

Welcome to my first tutorial on Flutter. I have never written any post on cross-platform or hybrid app framework but Flutter has changed this mindset of mine.

Previously, I have developed on React Native, Cordova, Phone Gap, Ionic and now of these really work out for me until I found Flutter along with its huge community of developers and its showcase apps.

What is Flutter?

In a nutshell, it is a multi-layered system, such that higher layers are easier to use and allow you to express a lot with little code and lower layers give you more control at the expense of having to deal with some complexity.

Flutter Framework is written entirely in Dart. Most of the engine is written in C++, with Android-specific parts written in Java, and iOS-specific parts written in Objective-C. Like React Native, Flutter also provides reactive-style views, but Flutter takes a different approach to avoid performance problems caused by the need for a JavaScript bridge by using a compiled programming language, namely Dart.

Dart is compiled “ahead of time” (AOT) into native code for multiple platforms. This allows Flutter to communicate with the platform without going through a JavaScript bridge that does a context switch. It also compiles to native code which in turn improves app startup times.

In Flutter, it is all about Widgets. Widgets are the elements that affect and control the view and interface to an app.

Flutter renders the widget tree and paints it to a platform canvas. This is nice and simple (and fast). It’s Hot-Reload capability allows real-time development experience.

You can read more about Flutter and learn about its goodness here.

Getting Started

Today, we will be building a very simple Flutter app that can be deployed on both iOS & Android called Contactly as we go through this tutorial. This is a very simple Contacts List app which will demonstrate the capabilities of Flutter. Capabilities include:

  1. TextField & Validations
  2. Button Clicks
  3. Navigations
  4. Image Rendering (Local & Online)
  5. Error Alert Dialog
  6. Scrollable List View
  7. List View Search
  8. JSON File Parsing
  9. JSON to Objects Mapping
  10. Opening External Web Browser

The final product of this app should look something like this:

It includes these features:

  1. TextField & Validations
  2. Button Clicks
  3. Navigations
  4. Image Rendering (Local & Online)
  5. Error Alert Dialog
  6. Scrollable List View
  7. List View Search
  8. JSON File Parsing
  9. JSON to Objects Mapping
  10. Opening External Web Browser
The Flutter’s Project Structure

While you haven’t built any apps using Flutter, let me give you a quick overview of its project structure. Later when you create a Flutter project, you should see a project structure as such:

  1. TextField & Validations
  2. Button Clicks
  3. Navigations
  4. Image Rendering (Local & Online)
  5. Error Alert Dialog
  6. Scrollable List View
  7. List View Search
  8. JSON File Parsing
  9. JSON to Objects Mapping
  10. Opening External Web Browser

I know you can’t wait to try out Flutter. Let’s dive in and set up all the required tools on your machine.

Installing Flutter

At the time of this writing, I’m using the following machine configuration and software version:

  1. TextField & Validations
  2. Button Clicks
  3. Navigations
  4. Image Rendering (Local & Online)
  5. Error Alert Dialog
  6. Scrollable List View
  7. List View Search
  8. JSON File Parsing
  9. JSON to Objects Mapping
  10. Opening External Web Browser

I cannot guarantee that my tutorial will work for every configuration and platform, hence, I will not include configuration troubleshooting here to keep this tutorial short and objective-oriented.

First up, head over to Flutter Installation page to install Flutter. I will skip the steps here as the steps in the document is detailed enough.

Once you run flutter doctor and you got (1~4 checked), you are good to go! It’s not necessary to have Connected Devices checked.

Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, v1.0.0, on Mac OS X 10.13.6 17G4015, locale en-SG)
[✓] Android toolchain - develop for Android devices (Android SDK 28.0.3)
[✓] iOS toolchain - develop for iOS devices (Xcode 10.1)
[✓] Android Studio (version 3.2)
[✓] Connected device (2 available)

If you have encountered any errors like below, follow the suggested solutions to fix it. For example, if your Mac has not installed with Android Studio, head over to this website to download the software. Just make sure you have the first 4 items checked before moving on.

Creating a new Flutter Project

With Flutter installed, now let’s start to build your first Flutter project.

First, fire up Android Studio and click Start a new Flutter Project.

Next, select Flutter Application and click Next.

Then fill in Project name as contactly, or anything you like. By default, it should show your default path of the Flutter path. In case it doesn’t work for you, navigate and specify your own Flutter SDK path. Optionally, you can change your project location and give a simple description. Then, click Next.

Finally, fill in a Company domain. This will be replicated in your Bundle Identifier (iOS) & Package Name (Android). For my case, I checked both Kotlin & Swift support. Then, click Finish.

Trying out an App on iOS Simulator

Once you started your Flutter Application, some boilerplate code is automatically generated with a sample app that allows you to hit a button and perform some text updates. Before we make any code changes, it is a good checkpoint to try running it on your iOS simulator.

To run the app, find the dropdown list somewhere at the top right that says , click on it and select Open iOS Simulator.

Your last selected simulator hardware will be chosen, which is iPhone XR for my case.

Click Run, which is the green triangle, and the app should open in your simulator. You should be able to interact with the Demo app and push a few buttons!

Building the Main Page

With the demo app running successfully, we are now ready to start building our first Flutter App!

Let’s start by deleting all the code in main.dart. Yes! Press command-a to select the whole code snippet and hit Delete.

Now we will begin to write the code from scratch. First, insert the following line of code to import the material package:

import 'package:flutter/material.dart';

This package is essential for building the UI of the app. To ensure that the app knows what to run after it finishes launching, add the main() method like this:

void main() => runApp(ContactlyApp());

It’s always a good practice to organize files into separate packages and put the constants in a separate. So, let’s create the helper package and the Constants.dart file to place some of our constant values we will be using in this app.

Right-click on the lib folder and then select New > Package. Name the package helpers.

Now we have a separate folder to store our helper classes. To create a new dart file, right-click on helpers and then select New > File. Name it Constants.dart.

In Constants.dart, insert the following code:

import 'package:flutter/material.dart';
 
// Colors
Color appDarkGreyColor = Color.fromRGBO(58, 66, 86, 1.0);
 
// Strings
const appTitle = "Contactly";

Here we import the same material package, so we can use the Color declaration and declare an appTitle to be used app-wide.

Now head back to main.dart and add this import statement after the first import line.

import 'helpers/Constants.dart';

Let’s start building our Main Page by adding these lines of codes:

class ContactlyApp extends StatelessWidget {
 
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: appTitle,
      theme: new ThemeData(
        primaryColor: appDarkGreyColor,
      ),
    );
  }
 
}

MaterialApp is one of the convenience widgets which allows customisations like adding navigation routes, appBar etc. Setting debugShowCheckedModeBanner to false will get rid of the Red Debug label at the top right. We use our declared appTitle in our constant file here to give it a title. Then, we set the primaryColor.

All the code looks good here and you might be eager to try running it. If you really did, you will get a huge red-colored error screen!

This is because we are not yet ready to paint the canvas. Be Patient!

In most tutorials, they will guide you on building everything into main.dart. But I find that we could make it cleaner by separating each page into separate files, which you will be eventually doing so when building production-ready apps.

Meanwhile, Android Studio should indicate an error in the widget_test.dart file. Since we change the class name from MyApp to ContactlyApp, you should change the following line of code from:

await tester.pumpWidget(MyApp());

to:

await tester.pumpWidget(ContactlyApp());

Building the Login Page

Now let’s go ahead to create a new page called LoginPage.dart and place it under lib. Perform the same ritual of importing material package.

Here we will be creating a Stateless Widget since we don’t need to store any form of data. You can find more details about Stateless VS Stateful here.

Before we go into the code, let’s look at how the login screen should look like:

As you can see, the screen has the following components:

  1. TextField & Validations
  2. Button Clicks
  3. Navigations
  4. Image Rendering (Local & Online)
  5. Error Alert Dialog
  6. Scrollable List View
  7. List View Search
  8. JSON File Parsing
  9. JSON to Objects Mapping
  10. Opening External Web Browser

To implement the screen component, insert the following code. Just copy & paste it first, we will go through them in awhile!

import 'package:flutter/material.dart';
import 'helpers/Constants.dart';
 
// 1
class LoginPage extends StatelessWidget {
 
  // 2
  final _pinCodeController = TextEditingController();
 
  // 3
  @override
  Widget build(BuildContext context) {
     // 3a
    final logo = CircleAvatar(
        backgroundColor: Colors.transparent,
        radius: bigRadius,
        child: appLogo,
    );
 
     // 3b
    final pinCode = TextFormField(
      controller: _pinCodeController,
      keyboardType: TextInputType.phone,
      maxLength: 4,
      maxLines: 1,
      autofocus: true,
      decoration: InputDecoration(
          hintText: pinCodeHintText,
          contentPadding: EdgeInsets.fromLTRB(20.0, 10.0, 20.0, 10.0),
          border: OutlineInputBorder(
            borderRadius: BorderRadius.circular(32.0),
          ),
          hintStyle: TextStyle(
              color: Colors.white
          )
      ),
      style: TextStyle(
        color: Colors.white,
      ),
    );
 
     // 3c
    final loginButton = Padding(
      padding: EdgeInsets.symmetric(vertical: 16.0),
      child: RaisedButton(
        shape: RoundedRectangleBorder(
          borderRadius: BorderRadius.circular(24),
        ),
        onPressed: () {},
        padding: EdgeInsets.all(12),
        color: appGreyColor,
        child: Text(loginButtonText, style: TextStyle(color: Colors.white)),
      ),
    );
 
     // 3d
    return Scaffold(
      backgroundColor: appDarkGreyColor,
      body: Center(
        child: ListView(
          shrinkWrap: true,
          padding: EdgeInsets.only(left: 24.0, right: 24.0),
          children: [
            logo,
            SizedBox(height: bigRadius),
            pinCode,
            SizedBox(height: buttonHeight),
            loginButton
          ],
        ),
      ),
    );
  }
}

And, for the Constants.dart file, please update it like this to add a number of constants that we use in the build method:

import 'package:flutter/material.dart';
 
// Colors
Color appDarkGreyColor = Color.fromRGBO(58, 66, 86, 1.0);
Color appGreyColor = Color.fromRGBO(64, 75, 96, .9);
 
// Strings
const appTitle = "Contactly";
const pinCodeHintText = "Pin Code";
const loginButtonText = "Login";
 
// Images
Image appLogo = Image.asset('assets/images/flutter-logo-round.png');
 
// Sizes
const bigRadius = 66.0;
const buttonHeight = 24.0;

OMG! That’s a huge chunk of code! Yes, but no worries. This is the first time we are really going deep into huge piles of the Dart code. Trust me, after going through these, you will get more familiar with how Flutter works 🙂

I have broken down this large piece of code into 3 major parts so that we can digest them easier:

  1. TextField & Validations
  2. Button Clicks
  3. Navigations
  4. Image Rendering (Local & Online)
  5. Error Alert Dialog
  6. Scrollable List View
  7. List View Search
  8. JSON File Parsing
  9. JSON to Objects Mapping
  10. Opening External Web Browser
  • First, we have our logo. It is embedded in a Circular Frame by using the CircularAvatar class. It also has an appLogo image.

If you run the app now, you will probably end up with an error saying that the image asset cannot be loaded. We know the path is given to load the Image but there are 2 missing pieces: the image itself and the path that we need to include in pubspec.yaml.

First, you can get the logo image I use from here. Then, create a new directory called assets in the root directory, and create a sub-directory called images.

Your image should be placed in root/assets/images.

Then, go to pubspec.yaml and add the following code to inform the app what assets to bundle together during runtime so it can be loaded.

assets:
    - assets/images/flutter-logo-round.png

Please note that you must add the configuration above to the flutter: section like this:

flutter:
  assets:
    - assets/images/flutter-logo-round.png

  • First, we have our logo. It is embedded in a Circular Frame by using the CircularAvatar class. It also has an appLogo image.

That was like an Effiel Tower of Codes! UI codes are tough 😭

Before we run the app, we also need to tell our main() to run LoginPage as the home page. So, head back to main.dart and add home: LoginPage() after theme. Your build code should look like this:

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: appTitle,
      theme: new ThemeData(
        primaryColor: appDarkGreyColor,
      ),
      home: LoginPage() // just added
    );
  }
 

Also, you will need to import LoginPage.dart at the very beginning of the file:

import 'LoginPage.dart';

Now run the app! You should see the Login Screen like this:

Cool, right? Let’s continue to build the rest of the screens.

Building Contacts List Page

Now we are warmed up a little, we can go a bit faster. We will now build the main feature of this app, the Contact List page. We will create a new file called HomePage.dart. Once you created the file, make sure you import material package:

import 'package:flutter/material.dart';

Contacts List Page will be a Stateful widget since we need to maintain the state of our contacts data. So add these first few lines of boilerplate codes:

class HomePage extends StatefulWidget {
 
  @override
  _HomePageState createState() {
    return _HomePageState();
  }
 
}
 
class _HomePageState extends State {
 
}

The first class HomePage will be called and used when navigating/presenting the page, while the private class _HomePageState will be called everytime the HomePage is called. This is also the mutable state object which we will maintain as the page get called.

Before we dive into coding again, let’s look at how our contact list screen looks like:

There are many things that we will need to do here:

  1. TextField & Validations
  2. Button Clicks
  3. Navigations
  4. Image Rendering (Local & Online)
  5. Error Alert Dialog
  6. Scrollable List View
  7. List View Search
  8. JSON File Parsing
  9. JSON to Objects Mapping
  10. Opening External Web Browser

Setting up the Routing

Let’s hook up our navigation route between LoginPage & HomePage. Head over to Constants.dart and add these tags:

// Pages
const loginPageTag = 'Login Page';
const homePageTag = 'Home Page';

Then, go to main.dart and add these just before our build function:

  final routes = {
    loginPageTag: (context) => LoginPage(),
    homePageTag: (context) => HomePage(),
  };
 

You will also need to import the HomePage.dart file:

 	
import 'HomePage.dart';

The code above allows us to use tags to associate each individual page. 🙂 Finally, let’s add the routes to our build function just after home.

  Widget build(BuildContext context) {
     ...
     home: LoginPage(),
     routes: routes
    );
  }

We can’t really test this out yet as we have not implemented the UI for our ListView. So, let’s do that first.

Populate JSON data and map to ListView

For this demo, I store all the contact data in a JSON file. You can download the sample JSON file here and create a data folder under assets. Put the records.json file into the folder. Then, update pubspec.yaml with the below asset configuration:

  assets:
    - assets/images/flutter-logo-round.png
    - assets/data/records.json

Now that we have prepared the JSON data, we will need to create:

  • First, we have our logo. It is embedded in a Circular Frame by using the CircularAvatar class. It also has an appLogo image.

Record Class to hold a Contact

First, let’s create a new models package under lib and create a new file named Record.dart. You can insert these lines of code into the file:

class Record {
  String name;
  String address;
  String contact;
  String photo;
  String url;
 
  Record({
    this.name,
    this.address,
    this.contact,
    this.photo,
    this.url
  });
 
  factory Record.fromJson(Map json){
    return new Record(
        name: json['name'],
        address: json['address'],
        contact: json ['contact'],
        photo: json['photo'],
        url: json['url']
    );
  }
}

Dart provides factory constructors to support the factory pattern. The factory constructor is able to return values (objects). Here it parses the given JSON string and returns a Record instance, which represents a contact.

RecordList Class to hold the list of Contacts

In the same models package, create another file called RecordList.dart. Then, put in these lines of code:

import 'Record.dart';
 
class RecordList {
  List records = new List();
 
  RecordList({
    this.records
  });
 
  factory RecordList.fromJson(List parsedJson) {
 
    List records = new List();
 
    records = parsedJson.map((i) => Record.fromJson(i)).toList();
 
    return new RecordList(
      records: records,
    );
  }
}

RecordService Class to perform the loading task

Lastly, create another file named RecordService.dart in the same package and insert the following code:

import 'RecordList.dart';
import 'package:flutter/services.dart' show rootBundle;
import 'dart:convert';
 
class RecordService {
 
  Future _loadRecordsAsset() async {
    return await rootBundle.loadString('assets/data/records.json');
  }
 
  Future loadRecords() async {
    String jsonString = await _loadRecordsAsset();
    final jsonResponse = json.decode(jsonString);
    RecordList records = new RecordList.fromJson(jsonResponse);
    return records;
  }
 
}

Here, the loadRecords() function parses the records.json file and map it into a RecordList object, holding a list of Record objects. The keyword Future should be new to you if you are unfamiliar with Dart. To perform asynchronous operation in Dart, we use futures. Future objects (futures) represent the results of asynchronous operations.

Implementing the Home Page to list the Contacts

Now let’s use what we have implemented in our HomePage. Open the HomePage.dart and add these import statements at the very beginning:

import 'models/Record.dart';
import 'models/RecordList.dart';
import 'models/RecordService.dart';

Other than listing the contact records, the home page has a search feature that lets users search the contacts. So, first, declare the following variables in the _HomePageState class of the HomePage.dart file:

final TextEditingController _filter = new TextEditingController();
 
RecordList _records = new RecordList();
RecordList _filteredRecords = new RecordList();
 
String _searchText = "";
 
Icon _searchIcon = new Icon(Icons.search);
 
Widget _appBarTitle = new Text(appTitle);

Here is the purpose of each variable:

  • First, we have our logo. It is embedded in a Circular Frame by using the CircularAvatar class. It also has an appLogo image.

Since it’s a Stateful widget, we can add some small settings when the state is initialized:

@override
  void initState() {
    super.initState();
 
    _records.records = new List();
    _filteredRecords.records = new List();
 
    _getRecords();
  }
 
  void _getRecords() async {
    RecordList records = await RecordService().loadRecords();
    setState(() {
      for (Record record in records.records) {
        this._records.records.add(record);
        this._filteredRecords.records.add(record);
      }
    });
  } 

In the init state of the home page, we empty our records data and get fresh data from the JSON file. Here we don’t need to really use an Async Call, but it is to introduce its concept and how you could call it if you were to perform a data fetch from a server.

Remember that in our previous section, we return a Scaffold in the build function as the main UI structure. So, continue to insert the following code to create the UI structure:

@override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: _buildBar(context),
      backgroundColor: appDarkGreyColor,
      body: _buildList(context),
      resizeToAvoidBottomPadding: false,
    );
  }

Like most ListView pages we have seen in mobile apps, there is a navigation bar at the top. In the code above, the appBar is the navigation bar. We specify to call _buildBar(context) to generate the bar, however, we haven’t implemented the function yet. So, continue to insert the following code:

Widget _buildBar(BuildContext context) {
    return new AppBar(
      elevation: 0.1,
      backgroundColor: appDarkGreyColor,
      centerTitle: true,
      title: _appBarTitle,
      leading: new IconButton(
            icon: _searchIcon
      )
    );
  }

Next, it’s the body. Again, we haven’t implemented the _buildList(context) function. Continue to add these lines of code:

Widget _buildList(BuildContext context) {
    if (!(_searchText.isEmpty)) {
    _filteredRecords.records = new List();
      for (int i = 0; i < _records.records.length; i++) {
        if (_records.records[i].name.toLowerCase().contains(_searchText.toLowerCase())
            || _records.records[i].address.toLowerCase().contains(_searchText.toLowerCase())) {
          _filteredRecords.records.add(_records.records[i]);
        }
      }
    }
 
    return ListView(
      padding: const EdgeInsets.only(top: 20.0),
      children: this._filteredRecords.records.map((data) => _buildListItem(context, data)).toList(),
    );
  }

Here, we handle the mapping of our RecordList data into our ListVew, and also handle any searches performed.

The final piece of our ListView is the UI for each ListViewItem. Let’s create the _buildListItem function:

Widget _buildListItem(BuildContext context, Record record) {
    return Card(
      key: ValueKey(record.name),
      elevation: 8.0,
      margin: new EdgeInsets.symmetric(horizontal: 10.0, vertical: 6.0),
      child: Container(
        decoration: BoxDecoration(color: Color.fromRGBO(64, 75, 96, .9)),
        child: ListTile(
          contentPadding:
          EdgeInsets.symmetric(horizontal: 20.0, vertical: 10.0),
          leading: Container(
              padding: EdgeInsets.only(right: 12.0),
              decoration: new BoxDecoration(
                  border: new Border(
                      right: new BorderSide(width: 1.0, color: Colors.white24))),
              child: Hero(
                  tag: "avatar_" + record.name,
                  child: CircleAvatar(
                    radius: 32,
                    backgroundImage: NetworkImage(record.photo),
                  )
              )
          ),
          title: Text(
            record.name,
            style: TextStyle(color: Colors.white, fontWeight: FontWeight.bold),
          ),
          subtitle: Row(
            children: [
              new Flexible(
                  child: new Column(
                      crossAxisAlignment: CrossAxisAlignment.start,
                      children: [
                        RichText(
                          text: TextSpan(
                            text: record.address,
                            style: TextStyle(color: Colors.white),
                          ),
                          maxLines: 3,
                          softWrap: true,
                        )
                      ]))
            ],
          ),
          trailing:
          Icon(Icons.keyboard_arrow_right, color: Colors.white, size: 30.0),
          onTap: () {},
        ),
      ),
    );
  }

This is a long chunky piece of code. We can again break down and digest this in a simpler way:

  1. TextField & Validations
  2. Button Clicks
  3. Navigations
  4. Image Rendering (Local & Online)
  5. Error Alert Dialog
  6. Scrollable List View
  7. List View Search
  8. JSON File Parsing
  9. JSON to Objects Mapping
  10. Opening External Web Browser
  • First, we have our logo. It is embedded in a Circular Frame by using the CircularAvatar class. It also has an appLogo image.

After implementing all these, it’s almost ready to run the app and test it out! One last thing to make it work is to handle the onPressed event of the login button. Previously, we haven’t specified anything in the implementation. Now go to LoginPage.dart and change the onPressed event of the loginButton variable to the following:

onPressed: () {
          Navigator.of(context).pushNamed(homePageTag);
        },

That’s it! Hit the run button and try to navigate the app from the login page to the home page!

Adding Search Feature

To allow search capability, we have to enable the text editor’s listener. Insert the code below after the _buildListItem method of the HomePage.dart file:

_HomePageState() {
    _filter.addListener(() {
      if (_filter.text.isEmpty) {
        setState(() {
          _searchText = "";
          _resetRecords();
        });
      } else {
        setState(() {
          _searchText = _filter.text;
        });
      }
    });
  }
 
  void _resetRecords() {
    this._filteredRecords.records = new List();
    for (Record record in _records.records) {
      this._filteredRecords.records.add(record);
    }
  }

The search process starts by tapping the search icon. When the search is triggered, we will perform some UI changes:

  1. TextField & Validations
  2. Button Clicks
  3. Navigations
  4. Image Rendering (Local & Online)
  5. Error Alert Dialog
  6. Scrollable List View
  7. List View Search
  8. JSON File Parsing
  9. JSON to Objects Mapping
  10. Opening External Web Browser

So here is the code you need. Continue to add the following method to handle the search:

void _searchPressed() {
    setState(() {
      if (this._searchIcon.icon == Icons.search) {
        this._searchIcon = new Icon(Icons.close);
        this._appBarTitle = new TextField(
          controller: _filter,
          style: new TextStyle(color: Colors.white),
          decoration: new InputDecoration(
            prefixIcon: new Icon(Icons.search, color: Colors.white),
            fillColor: Colors.white,
            hintText: 'Search by name',
            hintStyle: TextStyle(color: Colors.white),
          ),
        );
      } else {
        this._searchIcon = new Icon(Icons.search);
        this._appBarTitle = new Text(appTitle);
        _filter.clear();
      }
    });
  }

In order to trigger _searchPressed(), add this method in onPressed to _buildBar:

Widget _buildBar(BuildContext context) {
    ...
    icon: _searchIcon,
    onPressed: _searchPressed
    ... 
}  

Now you’re ready to go! Try running the app now and perform some searches! like “Mark”.

Building Contact Details Page

To finish up our Contactly App, let’s build our final Details Page to allow the app to show some more info about a contact. Let’s look at how the final screen looks like first:

It shows the contact’s profile image, its name, address, and phone number. One hidden feature not shown here is to allow user to navigate to an external web browser to view the technology’s website. So let’s get started!

In lib, create a new file called DetailsPage.dart and paste in the following code:

import 'package:flutter/material.dart';
import 'models/Record.dart';
 
// 1
class DetailPage extends StatelessWidget {
  final Record record;
  // 2
  DetailPage({this.record});
 
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
        appBar: new AppBar(
          title: new Text(record.name),
        ),
        body: new ListView(
            children: [
              Hero(
                tag: "avatar_" + record.name,
                child: new Image.network(
                    record.photo
                ),
              ),
              // 3
              GestureDetector(
                   onTap: () {
                     URLLauncher().launchURL(record.url);
                   },
                  child: new Container(
                    padding: const EdgeInsets.all(32.0),
                    child: new Row(
                      children: [
                        // First child in the Row for the name and the
                        // Release date information.
                        new Expanded(
                          // Name and Address are in the same column
                          child: new Column(
                            crossAxisAlignment: CrossAxisAlignment.start,
                            children: [
                              // Code to create the view for name.
                              new Container(
                                padding: const EdgeInsets.only(bottom: 8.0),
                                child: new Text(
                                  "Name: " + record.name,
                                  style: new TextStyle(
                                    fontWeight: FontWeight.bold,
                                  ),
                                ),
                              ),
                              // Code to create the view for address.
                              new Text(
                                "Address: " + record.address,
                                style: new TextStyle(
                                  color: Colors.grey[500],
                                ),
                              ),
                            ],
                          ),
                        ),
                        // Icon to indicate the phone number.
                        new Icon(
                          Icons.phone,
                          color: Colors.red[500],
                        ),
                        new Text(' ${record.contact}'),
                      ],
                    ),
                  )
              ),
            ]
        )
    );
  }
}

Here is what this above code does:

  1. TextField & Validations
  2. Button Clicks
  3. Navigations
  4. Image Rendering (Local & Online)
  5. Error Alert Dialog
  6. Scrollable List View
  7. List View Search
  8. JSON File Parsing
  9. JSON to Objects Mapping
  10. Opening External Web Browser
  • First, we have our logo. It is embedded in a Circular Frame by using the CircularAvatar class. It also has an appLogo image.

You should notice a new UI component called GestureDetector. As its name suggests, this widget class is designed to detect touches. When a user touches one of the fields, the app will call URLLauncher().launchURL(record.url) to load the URL in a web browser. This URLLauncher class is not ready yet.

Let’s create a new file called URLLauncher.dart in the helpers directory.

To perform a url launch, we need to install a new package called url-launcher. To do this, we need to update our pubspec.yaml like this:

Here we add a line of configuration to load the url_launcher. After editing, run flutter packages get by hitting the Packages Get button. This is how we install extra packages to increase the capabilities of our app 🙂 Great! You have just gained another skill!

Now go back to URLLauncher.dart, insert the following code to implement the launchURL method:

import 'package:url_launcher/url_launcher.dart';
 
class URLLauncher {
 
  launchURL(String url) async {
    if (await canLaunch(url)) {
      await launch(url);
    } else {
      throw 'Could not launch $url';
    }
  }
 
}

Head back to the DetailsPage.dart file and import the file we just implemented:

import 'helpers/URLLauncher.dart';

Great! The last step is to enable the navigation from HomePage to DetailsPage. Head back to HomePage.dart and edit the onTap: event of the _buildListItem method like this:

Widget _buildListItem(BuildContext context, Record record) {
            ...
          onTap: () {
            Navigator.push(
                context, MaterialPageRoute(builder: (context) => new DetailPage(record: record)));
          },
        ),
      ),
    );
  }  

Also, don’t forget to import the following file in HomePage.dart:

import 'DetailsPage.dart';

Viola! You are done with the app (not just iOS but Android too)! Run it and enjoy your great work 🙂

Conclusion

You have just gone through a very basic tutorial to get you started in developing on Flutter. In my own opinion, Flutter is developed based on the knowledge of popular mobile apps around where we can easily build UI components in just a few lines of codes. While its scalability is still questionable, we can see that Google and it’s community is investing a lot in this framework, and we could possibly forsee a bright future ahead for Flutter, striving past React Native.

You can download the finished project here.