Exploring React Native – Part 1.1

In the last article, titled “Exploring React Native”, we used a few components to create a simple app. The app consisted of an Image component, a couple Text components, data that changed with user interaction, and a couple of buttons created with the Button component and TouchableOpacity component.  We styled each component and at the end, had a counter app.

But there are a lot of components we did not cover and the ones we did cover, can be used in other ways. So, in this article, we will continue to use the project from the previous article to learn more about React Native’s components. The components we will be focusing on in this article are the ScrollView and View components. The ScrollView component is similar to View but allows for scrolling. The View component is one that we used in the previously but in this article, we will be using it to create sections in the app. As well, we will be passing a network image to the Image component and will learn a bit more about styling.

Let’s get started!

More Built In Components

I will be working on a Mac using Visual Studio Code as my editor, run the app on the iOS simulator and will be working with the “FirstRNProject” project. If you are using Windows or are targeting Android, I will test the app on the Android emulator at the end of the article. This code will also work if you are using Expo and will also be tested later on.

Open the App.js file and this is what we have from last time:

import React, { Component } from 'react';
import { Button, Image, StyleSheet, Text, TouchableOpacity, View } from 'react-native';
const styles = StyleSheet.create({
container: {
flex: 1,
backgroundColor: '#bff0d4',
alignItems: 'center',
},
image: {
height: 200,
width: 200,
marginTop: 100,
marginBottom: 20
},
question: {
fontSize: 30,
fontWeight: 'bold',
textAlign: 'center',
color: '#535B60',
padding: 20
},
number: {
fontSize: 60,
fontWeight: 'bold',
textAlign: 'center',
color: '#535B60',
padding: 20
},
plusButton: {
backgroundColor: '#9FC4AD',
width: 200,
borderRadius: 10,
margin: 10
},
minusButton: {
backgroundColor: '#BAAAC4',
width: 200,
borderRadius: 10,
margin: 10
},
buttonText: {
fontSize: 40,
fontWeight: 'bold',
textAlign: 'center',
color: '#535B60'
}
});
class App extends Component {
state = {
raccoons: 0
};
addMore = () => {
this.setState({
raccoons: this.state.raccoons + 1
})
}
removeOne = () => {
if(this.state.raccoons !== 0){
this.setState({
raccoons: this.state.raccoons - 1
})
}
}
render() {
return (
<View style={styles.container}>
<Image style={styles.image} resizeMode='contain' source={require('./img/raccoon.png')} />
<Text style={styles.question} >How many raccoons did you see last night?</Text>
<Text style={styles.number}>{this.state.raccoons}</Text>
<TouchableOpacity onPress={this.addMore} style={styles.plusButton} >
<Text style={styles.buttonText}>PLUS</Text>
</TouchableOpacity>
<TouchableOpacity onPress={this.removeOne} style={styles.minusButton}>
<Text style={styles.buttonText}>MINUS</Text>
</TouchableOpacity>
</View>
)
}
}
export default App;

First a quick recap of the code above.

We first imported the components we were going to use from React Native. These components were the Button, Image, StyleSheet, Text, TouchableOpacity and View components. Then we created a styles variables that contained all the styling objects we used to style the components. After that, we created a state for the counter which would change with the pressing of either “PLUS” or “MINUS” buttons. Then inside the render function we had a View component that wrapped the Image, Text and TouchableOpacity components and each was styled accordingly.

Open the Terminal or Command Prompt to run the project. If you are using Visual Studio Code, there is an “integrated terminal, initially starting at the root of your workspace.” Using this terminal, you can run the React Native iOS/Android start commands, or if using Expo, the Expo start command from the editor. You can learn more about Visual Studio Code’s terminal here, https://code.visualstudio.com/docs/editor/integrated-terminal. What you will have is the following:

The app looks great but what if we wanted to create a list of animals, each with its own image, text, counter and buttons? Well, let’s copy the components between the View tags and paste them right after the “MINUS” button but before the closing View tag. Your code will look like this:

<View style={styles.container}>
{/* Raccoon One */}
<Image style={styles.image} resizeMode='contain' source={require('./img/raccoon.png')} />
<Text style={styles.question} >How many raccoons did you see last night?</Text>
<Text style={styles.number}>{this.state.raccoons}</Text>
<TouchableOpacity onPress={this.addMore} style={styles.plusButton} >
<Text style={styles.buttonText}>PLUS</Text>
</TouchableOpacity>
<TouchableOpacity onPress={this.removeOne} style={styles.minusButton}>
<Text style={styles.buttonText}>MINUS</Text>
</TouchableOpacity>
{/* Raccoon Two */}
<Image style={styles.image} resizeMode='contain' source={require('./img/raccoon.png')} />
<Text style={styles.question} >How many raccoons did you see last night?</Text>
<Text style={styles.number}>{this.state.raccoons}</Text>
<TouchableOpacity onPress={this.addMore} style={styles.plusButton} >
<Text style={styles.buttonText}>PLUS</Text>
</TouchableOpacity>
<TouchableOpacity onPress={this.removeOne} style={styles.minusButton}>
<Text style={styles.buttonText}>MINUS</Text>
</TouchableOpacity>
</View>

When you save the file and reload the app, you will see this:

That doesn’t look right. We can barely see that there is another image of a raccoon at the bottom of the screen and we can’t scroll down to view the rest of the app. In order for the app to scroll we will use the ScrollView component. According to the React Native documentation, “The ScrollView is a generic scrolling container that can host multiple components and views.” There is another option we could use, called FlatList. The difference between the two, is that, ScrollView renders all of its children components, or the components between its tags, at once. While FlatList renders its items when they appear on the screen and removes them once off the screen. Therefore, if you have a large list, using ScrollView will slow down rendering and increase memory usage. For this app, our list will be short and ScrollView will be used but in later articles we will be using the FlatList component.

Let’s first import the ScrollView component and replace the View tags with ScrollView, save the file and reload. This is what will happen:

This error occurs because of the layout prop “alignItems: ‘center’” that is passed to the styling of the ScrollView components. To fix it remove “alignItems: ‘center’” from “container” in styles. Save the file, reload and now the app will look like this:

It’s not perfect but we can now scroll to through the app and see the second image, along with the text and buttons. To fix the styling of the images and buttons simply add “alignSelf: ‘center’” to the “image”, “plusButton” and “minusButton” styles.

image: {
height: 200,
width: 200,
marginTop: 100,
marginBottom: 20,
alignSelf: 'center'
},
plusButton: {
backgroundColor: '#9FC4AD',
width: 200,
borderRadius: 10,
margin: 10,
alignSelf: 'center'
},
minusButton: {
backgroundColor: '#BAAAC4',
width: 200,
borderRadius: 10,
margin: 10,
alignSelf: 'center'
},

Great! Everything is now centered and we can scroll.

It doesn’t make sense to keep track of the number of raccoons twice, so let’s find an image of another animal online.

If you recall, in the previous article we saved the image of the raccoon in our project under the ‘img’ folder, then passed it to the Image component. By doing so we were using a static image. The Image component can display various types of images and what I want to do now is use a network image. I went online and found an image of a pigeon and got the URL to the image.

Now if you replace the location of the second raccoon image with an URL, like this:

<Image style={styles.image} resizeMode='contain' source={require('https://cdn.pixabay.com/photo/2012/04/02/12/43/pigeon-24391_1280.png')} />

Then you will get an error like this:

That’s because, passing a network image is a little different than passing a static image. Inside of “source={}”, replace it with “{uri: ‘URL_OF_THE_IMAGE’}”. It will look like this:

<Image style={styles.image} resizeMode='contain' source={{ uri: ‘URL_OF_THE_IMAGE’ }} />

So if we replace ‘URL_OF_THE_IMAGE’ with the actual URL, we will have this:

<Image style={styles.image} resizeMode='contain' source={{ uri: 'https://cdn.pixabay.com/photo/2012/04/02/12/43/pigeon-24391_1280.png' }} />

Another key difference between static and network images is that, network images require that the dimensions of the image be specified. Our ‘image’ style object has specified width and height dimension, so our image will appear. Had those dimension not been there, the image would not be displayed.

Save the file and reload the app to get this:

Now I know not everyone likes this bird but I liked how it looked and it a bird, I would say, most people see on a regular basis. You can choose another bird or another animal entirely, it’s totally up to you. There’s just a couple more things that need changing, such as the text, adding the new counter data to the state and creating new functions for the new pigeon buttons.

Changing the text is simple, go to the Text component that corresponds to the second animal, in my case the pigeon, and change it to something like, “How many pigeons did you see today?”. Then add “pigeons: 0” to the state and replace “{this.state.raccoons}” with “{this.state.pigeons}” in the following Text component. Next we can rename the existing functions for the buttons to “addRaccoons” and “removeRaccoons” then copy and paste them right below. For the second set of functions, replace “raccoons” with “pigeons”. Remember to keep the camel case coding style and capitalize the “P” in pigeon. Also don’t forget to go to the TouchableOpacity components and rename the functions accordingly. If you are having any issues, here is the code:

class App extends Component {
state = {
raccoons: 0,
pigeons: 0
};
//Raccoon Functions
addRaccoons = () => {
this.setState({
raccoons: this.state.raccoons + 1
})
}
removeRaccoons = () => {
if(this.state.raccoons !== 0){
this.setState({
raccoons: this.state.raccoons - 1
})
}
}
//Pigeon Functions
addPigeons = () => {
this.setState({
pigeons: this.state.pigeons + 1
})
}
removePigeons = () => {
if(this.state.pigeons !== 0){
this.setState({
pigeons: this.state.pigeons - 1
})
}
}
render() {
return (
<ScrollView style={styles.container}>
{/* Raccoon */}
<Image style={styles.image} resizeMode='contain' source={require('./img/raccoon.png')} />
<Text style={styles.question} >How many raccoons did you see last night?</Text>
<Text style={styles.number}>{this.state.raccoons}</Text>
<TouchableOpacity onPress={this.addRaccoons} style={styles.plusButton} >
<Text style={styles.buttonText}>PLUS</Text>
</TouchableOpacity>
<TouchableOpacity onPress={this.removeRaccoons} style={styles.minusButton}>
<Text style={styles.buttonText}>MINUS</Text>
</TouchableOpacity>
{/* Pigeon */}
<Image style={styles.image} resizeMode='contain' source={{ uri: 'https://cdn.pixabay.com/photo/2012/04/02/12/43/pigeon-24391_1280.png' }} />
<Text style={styles.question} >How many pigeons did you see today?</Text>
<Text style={styles.number}>{this.state.pigeons}</Text>
<TouchableOpacity onPress={this.addPigeons} style={styles.plusButton} >
<Text style={styles.buttonText}>PLUS</Text>
</TouchableOpacity>
<TouchableOpacity onPress={this.removePigeons} style={styles.minusButton}>
<Text style={styles.buttonText}>MINUS</Text>
</TouchableOpacity>
</ScrollView>
)
}
}

I’ve added comments, “{/* Raccoon */}” and “{/* Pigeon */}”, to help indicate that the following set of code corresponds to a particular animal. Writing comments can help you identify sections of code, especially once the code starts to get long and complicated. One thing to note is that when commenting inside JSX, where tags are used like in the above, you need to wrap the comment inside of “{/* YOUR_COMMENT */}”. Outside of JSX, you can use “// YOUR_COMMENT” for a single line comment or “/* YOUR_COMMENT */” for a multi-line comment.

Once saved and reloaded, you will be able to scroll through the app and press the buttons to increase or decrease the counters. Here is how it will look:

Great! Let’s now work on styling the app a bit more by using React Native’s View component.

Right now the app is one continuous page with images, text and buttons. To help separate each section and make the app more user friendly, we will create a border around the raccoon and pigeon set of components. It’s like creating a card for each animal and the card contains all the content for that one subject. This can simply be done by wrapping each set of components in a View and passing it a set of styles.

First, import the View component if you deleted it and create two set of opening and closing View tags. Then copy the set of raccoon components and paste them inside the first View. Repeat for the pigeon components but paste those in the second View. This is what you should have:

<ScrollView style={styles.container}>
{/* Raccoon */}
{/* First View */}
<View>
<Image style={styles.image} resizeMode='contain' source={require('./img/raccoon.png')} />
<Text style={styles.question} >How many raccoons did you see last night?</Text>
<Text style={styles.number}>{this.state.raccoons}</Text>
<TouchableOpacity onPress={this.addRaccoons} style={styles.plusButton} >
<Text style={styles.buttonText}>PLUS</Text>
</TouchableOpacity>
<TouchableOpacity onPress={this.removeRaccoons} style={styles.minusButton}>
<Text style={styles.buttonText}>MINUS</Text>
</TouchableOpacity>
</View>
{/* Pigeon */}
{/* Second View */}
<View>
<Image style={styles.image} resizeMode='contain' source={{ uri: 'https://cdn.pixabay.com/photo/2012/04/02/12/43/pigeon-24391_1280.png' }} />
<Text style={styles.question} >How many pigeons did you see today?</Text>
<Text style={styles.number}>{this.state.pigeons}</Text>
<TouchableOpacity onPress={this.addPigeons} style={styles.plusButton} >
<Text style={styles.buttonText}>PLUS</Text>
</TouchableOpacity>
<TouchableOpacity onPress={this.removePigeons} style={styles.minusButton}>
<Text style={styles.buttonText}>MINUS</Text>
</TouchableOpacity>
</View>
</ScrollView>

We will now create a new set of styles called “cardStyle” and pass it to both View components. To “cardStyle”, we will add a border color and width. This will create the border around each set of components.

cardStyle: {
borderColor: '#535B60',
borderWidth: 2
}

Save the file and reload the app. Wait a minute, this doesn’t look right.

I can see that there is a line separating the raccoon and pigeon cards but that’s about it. We will need to style this some more.

First add “margin: 20” to “cardStyle”, this will create space between the outside of the border and the edge of the screen. We can then go into the “image” style and remove both margins.

Looking better but I don’t like the border, it’s too boxy. This is a quick fix, add “borderRadius: 10” to “cardStyle”. Also notice that the top border of the raccoon card is being cut off by the iPhone X notch. Let’s add “paddingTop: 20” to the “container” style.

Looking awesome! Our styling is as follows:

const styles = StyleSheet.create({
container: {
flex: 1,
backgroundColor: '#bff0d4',
paddingTop: 20
},
image: {
height: 200,
width: 200,
alignSelf: 'center'
},
question: {
fontSize: 30,
fontWeight: 'bold',
textAlign: 'center',
color: '#535B60',
padding: 20
},
number: {
fontSize: 60,
fontWeight: 'bold',
textAlign: 'center',
color: '#535B60',
padding: 20
},
plusButton: {
backgroundColor: '#9FC4AD',
width: 200,
borderRadius: 10,
margin: 10,
alignSelf: 'center'
},
minusButton: {
backgroundColor: '#BAAAC4',
width: 200,
borderRadius: 10,
margin: 10,
alignSelf: 'center'
},
buttonText: {
fontSize: 40,
fontWeight: 'bold',
textAlign: 'center',
color: '#535B60'
},
cardStyle: {
borderColor: '#535B60',
borderWidth: 2,
margin: 20,
borderRadius: 10,
}
});

Before continuing with styling, I would like to over the different ways you can style a component.

Although not mentioned before, you can simply pass styles to a component using inline styling. Here is an example:

<View style={{ flex: 1, borderColor: ‘red’, borderWidth: 2 }} >

Or, as we have been doing, we can put all the styling in one location and reference it when needed like this:

const styles = StyleSheet.create({
container: {
flex: 1,
borderColor: ‘red’,
borderWidth: 2
}
});
<View style={styles.cardStyle}>

Both styling methods will style the component the same, but by having the styling outside of the render function, we are making the code cleaner and easier to read.

We can also mix and use both by passing style an array, which can help has pass specific styling to only one particular component, while also passing a set of styles other components use. Here is an example:

<View style={[ styles.container, { margin: 20 } ]} >

The styling is almost perfect but I want to add a bottom margin to the pigeon’s View component because I want some spacing between the bottom of the screen and the bottom of the pigeon card. We will pass “cardStyle” and “marginBottom: 60” to only the second View component. Here is how it is done:

{/* Pigeon */}
{/* Second View */}
<View style={[styles.cardStyle, {marginBottom: 60}]}>
<Image style={styles.image} resizeMode='contain' source={{ uri: 'https://cdn.pixabay.com/photo/2012/04/02/12/43/pigeon-24391_1280.png' }} />
<Text style={styles.question} >How many pigeons did you see today?</Text>
<Text style={styles.number}>{this.state.pigeons}</Text>
<TouchableOpacity onPress={this.addPigeons} style={styles.plusButton} >
<Text style={styles.buttonText}>PLUS</Text>
</TouchableOpacity>
<TouchableOpacity onPress={this.removePigeons} style={styles.minusButton}>
<Text style={styles.buttonText}>MINUS</Text>
</TouchableOpacity>
</View>

The bottom of the pigeon card is visible. This is looking great!

Continuing to focus on styling, let’s have the two buttons placed next to each other. Here we will be using the View component again. First inside the raccoon’s View component create a View right after the counter text. Then copy and paste both TouchableOpacity components inside of the View tags. Then inside the pigeon’s View component, do the same for those buttons.

<ScrollView style={styles.container}>
{/* Raccoon */}
<View style={styles.cardStyle}>
<Image style={styles.image} resizeMode='contain' source={require('./img/raccoon.png')} />
<Text style={styles.question} >How many raccoons did you see last night?</Text>
<Text style={styles.number}>{this.state.raccoons}</Text>
{/* Raccoon Buttons */}
<View>
<TouchableOpacity onPress={this.addRaccoons} style={styles.plusButton} >
<Text style={styles.buttonText}>PLUS</Text>
</TouchableOpacity>
<TouchableOpacity onPress={this.removeRaccoons} style={styles.minusButton}>
<Text style={styles.buttonText}>MINUS</Text>
</TouchableOpacity>
</View>
</View>
{/* Pigeon */}
<View style={[styles.cardStyle, {marginBottom: 60}]}>
<Image style={styles.image} resizeMode='contain' source={{ uri: 'https://cdn.pixabay.com/photo/2012/04/02/12/43/pigeon-24391_1280.png' }} />
<Text style={styles.question} >How many pigeons did you see today?</Text>
<Text style={styles.number}>{this.state.pigeons}</Text>
{/* Pigeon Buttons */}
<View>
<TouchableOpacity onPress={this.addPigeons} style={styles.plusButton} >
<Text style={styles.buttonText}>PLUS</Text>
</TouchableOpacity>
<TouchableOpacity onPress={this.removePigeons} style={styles.minusButton}>
<Text style={styles.buttonText}>MINUS</Text>
</TouchableOpacity>
</View>
</View>
</ScrollView>

If you save the file and reload the app, you will notice that nothing happens. We will need to create a new style called “buttonRow”, pass it “flexDirection: ‘row’”, then pass this style to the buttons’ View components. By default “flexDirection” is set to column, because of this, components are stacked on top of each other. But by setting “flexDirection” to row, the components in that View will be stacked side by side.

buttonRow: {
flexDirection: 'row'
}
{/* Raccoon Button */}
<View style={styles.buttonRow}>
<TouchableOpacity onPress={this.addRaccoons} style={styles.plusButton} >
<Text style={styles.buttonText}>PLUS</Text>
</TouchableOpacity>
<TouchableOpacity onPress={this.removeRaccoons} style={styles.minusButton}>
<Text style={styles.buttonText}>MINUS</Text>
</TouchableOpacity>
</View>
{/* Pigeon Buttons */}
<View style={styles.buttonRow}>
<TouchableOpacity onPress={this.addPigeons} style={styles.plusButton} >
<Text style={styles.buttonText}>PLUS</Text>
</TouchableOpacity>
<TouchableOpacity onPress={this.removePigeons} style={styles.minusButton}>
<Text style={styles.buttonText}>MINUS</Text>
</TouchableOpacity>
</View>

Now the app looks like this:

Oh no! The buttons don’t fit properly. Let’s make the buttons smaller by changing the text’s size and decreasing its width.

plusButton: {
backgroundColor: '#9FC4AD',
width: 150,
borderRadius: 10,
margin: 10,
alignSelf: 'center'
},
minusButton: {
backgroundColor: '#BAAAC4',
width: 150,
borderRadius: 10,
margin: 10,
alignSelf: 'center'
},
buttonText: {
fontSize: 30,
fontWeight: 'bold',
textAlign: 'center',
color: '#535B60'
},

Better but still needs work. We can decrease the button’s margins and center the button’s View component.

plusButton: {
backgroundColor: '#9FC4AD',
width: 150,
borderRadius: 10,
margin: 5,
alignSelf: 'center'
},
minusButton: {
backgroundColor: '#BAAAC4',
width: 150,
borderRadius: 10,
margin: 5,
alignSelf: 'center'
},
buttonText: {
fontSize: 30,
fontWeight: 'bold',
textAlign: 'center',
color: '#535B60'
},
buttonRow: {
flexDirection: 'row',
alignSelf: 'center'
}

At this point, the app looks wonderful but I have tested our code only on the iOS simulator. I want to make sure for those using Windows or targeting Android, that we have the same results. After opening the Android emulator and running the project, I have this:

The app works! I knew it would but there are times that certain components appear differently on iOS than they do on Android. We saw these differences when working with React Native’s Button component. But in this case, the app looks and works the same on both Android and iOS.

Now for those using Expo, I mentioned at the beginning that the code used in this project would also work for you guys. To ensure this is true, I am going to copy the code and paste it in an Expo project we created a while back called, “FirstExpoProject”. Here is the app on a real iPhone X Max:

Yes, app works and looks great! It could probably use more padding at the top and bottom of the screen. Unfortunately, I do not own an Android device but since the app worked on the Android emulator, I am certain it will work on an Android device.

This is where we will leave off for this article. We added ScrollView to our app, allowing us to the ability to scroll and add more content. Then we added a new animal and passed a network image to the Image component. Lastly, using View and some new styling skills we created cards to contain each subject. I suggest you play around with the code because following steps is one thing but when you try it on your own, that’s when you really learn.

In the next article, we will continue to expand our React Native skills using this project. The code in this project was getting long and could be cleaned up. For one, we will learn about creating components and a few more things. See you in the next article.

Exploring React Native

In the previous article, titled “Getting Started with React Native”, we briefly went over what React Native is. We went through the installation process for the Expo CLI and the React Native CLI. The last thing we did was create an Expo and React Native project and made changes to the code, then run the projects.

But at the end of the article you may have wondered, “Now what?”. In this article I will show you some of the built in components that come with React Native. We will use these components to create a fairly simply one screen app that will keep track of a number that can be increased and decreased by a button. The app will teach you how to add an image, text, buttons, keep track of data and style all these components.

Let’s begin!

Built In Components

Begin by opening your project in the code editor of your choice, remember I use Visual Studio Code. If you recall, in the last article there were two ways to create a project. We created an Expo project, called “FirstExpoProject,” and a React Native project, called “FirstRNProject”. I will be using the “FirstRNProject” project but the code in this article will work for both.

In the Explorer, select App.js, open it and delete all the code inside of the file. Throughout this article I will be showing you the code I write, some times it will only be a snippet of the file and I will use “…” to indicate there is more code above and/or below that snippet. At the end of the article I will post the entire code for the App.js file.

The first two line of code will be the following:

import React, { Component } from ‘react’;
import { StyleSheet, Text, View } from ‘react-native’;

The second line is important to us because this is where we will be importing all of the built in components. The StyleSheet allows us to create a specific set of styles for our components, Text component allows us to create text and the View component is one of the fundamental components for the user interface. To learn more about this components and the others provided by React Native check out this link, https://facebook.github.io/react-native/docs/components-and-apis.

Next, create a variable named styles. This is where we will create a StyleSheet and style our components.

const styles = StyleSheet.create({

)};

Time to create the class and export it. Here is how the code will look:

class App extends Component {

}
export default App;

Inside the class, we need to add the render function and return our View component. Save the file.

class App extends Component {
   render() {
     return (
     <View />
     )
   }
}

At this point we can run the app. As I mentioned before I am using the project we created with the React Native CLI, therefore I will open a Terminal on my Mac and head to the directory where the project is located and enter the following command:

react-native run-ios

If you are using Windows or simply want to test on Android, type the following into the Terminal or Command Prompt:

react-native run-android

If you decided to work with the Expo project, type the following into the Terminal or Command Prompt and use one of the methods from the previous article to run the app on your phone or simulator/emulator:

expo start

Again, I am using a Mac and for the time being will be using the iOS simulator. Later on I will use the Android emulator to point out some styling differences.

What you will see when the app is up and running is a white, blank screen. Here is the app running on the iOS simulator:

A blank, white screen looks dull, let’s change that by adding some color to the background:

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#bff0d4'
  }
});

class App extends Component {
   render() {
     return (
     <View style={styles.container} />
   )
   }
}

First we add a style prop to the View component. In styles we create a style “container” and gave it a flex of 1 and a background color. “flex: 1”, simply tells the View component to take up all the space available. To learn more about flex, go here https://facebook.github.io/react-native/docs/height-and-width. The color give to the “backgroundColor” can be written in a few ways for React Native, here is a link to learn more, https://facebook.github.io/react-native/docs/colors. If you’ve ever done web development and used CSS, the way to style these components will look familiar. Save the file and if you don’t see the change, reload the simulator/emulator. You can reload by pressing the “Command” and “R” keys for the iOS simulator. For Android emulator, tap “R” twice.

Ok now that we have some color, why not add an image to our app. First thing you need is an image. I found one online of a raccoon, download it and put in a new folder I created inside the project called “img”. But you can also use different type of images, such as using an URL for an image found online. Some of types of images need to have a specific height and width passed to it. Learn more here, https://facebook.github.io/react-native/docs/image. Let’s import the Image component.

import { Image, StyleSheet, Text, View } from 'react-native';

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#bff0d4',
    alignItems: 'center',
  }
});

class App extends Component {
  render() {
    return (
    <View style={styles.container}>
    <Image resizeMode='center' source={require('./img/raccoon.png')} />
    </View>
    )
  }
}

Inside the “container” style, I added “alignItems: ‘center’” which centers all the components inside of View horizontally. Next, inside the View component I added the Image component and gave the source the location to the image of the raccoon I am using. I also added “resizeMode=’center’” because the image was large and not displaying properly, this will center the image in the view. Here is what I end up with:

You see that the image is still too large, so we are going to change that.

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#bff0d4',
    alignItems: 'center',
  },
  image: {
    height: 200,
    width: 200
  }
});

class App extends Component {
  render() {
    return (
      <View style={styles.container}>
      <Image style={styles.image} resizeMode='contain' source={require('./img/raccoon.png')} />
      </View>
    )
  }
}

Create a new style named “image” and give it a height and width. Pass the style to the Image component and change the “resizeMode” to “contain”. This will ensure the image is resized properly to fit the height and width given.

You will notice the image is too close to the top of the screen and a piece of the ears are cut off. To fix this, add “marginTop” and give it a value of 100. You can play around with the number to get the desired spacing between the top of the screen and the image.

image: {
  height: 200,
  width: 200,
  marginTop: 100
}

Here is what we have:

Inside the View component and right below the Image component, lets add a Text component with the following text, “How many raccoons did you see last night?”.

return (
  <View style={styles.container}>
  <Image style={styles.image} resizeMode='contain' source={require('./img/raccoon.png')} />
  <Text>How many raccoons did you see last night?</Text>
  </View>
)

The text will appear right below the image but it needs some styling. Create a new style named “question” and give it a font size of 20, make it bold, center and change the color. Don’t forget to pass the prop in the Text component.

<Text style={styles.question}>How many raccoons did you see last night?</Text>
question: {
   fontSize: 20,
   fontWeight: 'bold',
   textAlign: 'center',
   color: '#535B60'
}

Looking much better. Next add a new Text component underneath the question which will track the number of raccoons you see. The styling will be similar to that of the question but the font size will be much bigger.

<Text style={styles.number} >0</Text>
number: {
   fontSize: 60,
   fontWeight: 'bold',
   textAlign: 'center',
   color: '#535B60'
}

Here is what we now have:

When we see a raccoon, we will need to be able to press a button which will increase the number or decrease the number. React Native comes with a built in component called Button and we will use it to create a button for increasing the value. Later on, we will use another component that allows for more customization.

import { Button, Image, StyleSheet, Text, View } from 'react-native';
<View style={styles.container}>
  <Image style={styles.image} resizeMode='contain' source={require('./img/raccoon.png')} />
  <Text style={styles.question} >How many raccoons did you see last night?</Text>
  <Text style={styles.number}>0</Text>
  <Button title='PLUS' color='#535B60' />
</View>

Let’s add the Button component right after the Text component display the number. We pass it a title, “PLUS”, and a color. At the moment our button does not do anything. One thing about the Button component is that they look different on iOS than they do on Android. I am going to run the Android emulator and show you the difference.

Here is the button on Android:

And here is the button on iOS:

Notice how on Android the button has “PLUS” in a white font and is surrounded by the color we provided. But on iOS only the text “PLUS” appears and it is in the color we provided. This is something you will notice when working with React Native and you will need to style your components accordingly.

Before telling the button what to do every time it is pressed, lets create a state that will store our number data. Currently, the number of raccoons seen is set to zero but we want it to change with the pressing of the button.

Create a state with “raccoons” set to zero inside of the class App and before the render function. Then use the data to replace the hard coded zero in the Text component.

class App extends Component {
  state = {
    raccoons: 0
  };

render() {
  return (
    <View style={styles.container}>
    <Image style={styles.image} resizeMode='contain' source={require('./img/raccoon.png')} />
    <Text style={styles.question} >How many raccoons did you see last night?</Text>
    <Text style={styles.number}>{this.state.raccoons}</Text>

Notice how I replaced the “0” in the second Text component with “{this.state.raccoons}”, this calls “raccoons” in the state. Change the “0” in the state to another number, save, and see that it changes.

We’re now ready to make our button do something. Create a function called “addMore” and set “raccoons” to increase by 1. Then in the Button component, add the prop “onPress” and pass it the “addMore” function.

addMore = () => {
  this.setState({
    raccoons: this.state.raccoons + 1
  })
}
<Button onPress={this.addMore} title='PLUS' color='#535B60' />

Save the file and see that when you press the button, the counter will increase by one. Here is how it will look:

We can increase the counter but what if we made a mistake and want to decrease the counter? Well, we can create another button that will do just that. This time we will use TouchableOpacity component to create a custom button. Begin by importing TouchableOpacity and adding the component right after the Button component we have in the class. We will wrap the TouchableOpacity around a Text component.

import { Button, Image, StyleSheet, Text, TouchableOpacity, View } from 'react-native';
<Button onPress={this.addMore} title='PLUS' color='#535B60' />

<TouchableOpacity>
<Text>MINUS</Text>
</TouchableOpacity>

Save the file and see that the button needs some styling. We will add styling to the text to change the font size but also to the TouchableOpacity component to make it stand out.

button: {
  backgroundColor: '#BAAAC4',
  width: 200,
  borderRadius: 10
},
buttonText: {
  fontSize: 40,
  fontWeight: 'bold',
  textAlign: 'center',
  color: '#535B60'
}
<TouchableOpacity style={styles.button}>
<Text style={styles.buttonText}>MINUS</Text>
</TouchableOpacity>

We will give the TouchableOpacity component a background color, width of 200 and border radius of 10 to round the corners. To the Text, same as before, font size of 40, bold, align it to the center and give a color. Here is how it will look:

The “Minus” button currently does nothing. We will create a function and pass it to the TouchableOpacity component, just like we did to the Button component.

removeOne = () => {
  this.setState({
    raccoons: this.state.raccoons - 1
  })
}
<TouchableOpacity onPress={this.removeOne} style={styles.button}>
<Text style={styles.buttonText}>MINUS</Text>
</TouchableOpacity>

Test the app! You can add to the counter and remove from it as well. The “MINUS” button is working but it should stop when it reaches zero, we can’t see a negative number of raccoons. This can be easily fixed by adding an if statement to check the current value of “raccoons”.

removeOne = () => {
  if(this.state.raccoons !== 0){
    this.setState({
      raccoons: this.state.raccoons - 1
    })
  }
}

Before calling this app complete, let’s make the “PLUS” button look like the “MINUS” button and do some other styling changes.

import React, { Component } from 'react';
import { Image, StyleSheet, Text, TouchableOpacity, View } from 'react-native';

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#bff0d4',
    alignItems: 'center',
  },
  image: {
    height: 200,
    width: 200,
    marginTop: 100,
    marginBottom: 20
  },
  question: {
    fontSize: 30,
    fontWeight: 'bold',
    textAlign: 'center',
    color: '#535B60',
    padding: 20
  },
  number: {
    fontSize: 60,
    fontWeight: 'bold',
    textAlign: 'center',
    color: '#535B60',
    padding: 20
  },
  plusButton: {
    backgroundColor: '#9FC4AD',
    width: 200,
    borderRadius: 10,
    margin: 10
  },
  minusButton: {
    backgroundColor: '#BAAAC4',
    width: 200,
    borderRadius: 10,
    margin: 10
  },
  buttonText: {
    fontSize: 40,
    fontWeight: 'bold',
    textAlign: 'center',
    color: '#535B60'
  }
});

class App extends Component {
  state = {
    raccoons: 0
  };

  addMore = () => {
    this.setState({
      raccoons: this.state.raccoons + 1
    })
  }
  removeOne = () => {
    if(this.state.raccoons !== 0){
      this.setState({
        raccoons: this.state.raccoons - 1
      })
    }
}

  render() {
    return (
      <View style={styles.container}>
      <Image style={styles.image} resizeMode='contain' source={require('./img/raccoon.png')} />
      <Text style={styles.question} >How many raccoons did you see last night?</Text>

      <Text style={styles.number}>{this.state.raccoons}</Text>

      <TouchableOpacity onPress={this.addMore} style={styles.plusButton} >
      <Text style={styles.buttonText}>PLUS</Text>
      </TouchableOpacity>

      <TouchableOpacity onPress={this.removeOne} style={styles.minusButton}>
      <Text style={styles.buttonText}>MINUS</Text>
      </TouchableOpacity>
      </View>
    )
  }
}

export default App;

First, replace the Button component with a TouchableOpacity component wrapped around a Text component. Pass the “buttonText” style to the Text and the “addMore” function to the TouchableOpacity. Next I wanted to differentiate the two buttons, so I created another style named “plusButton” and renamed “button” to “minusButton”, then passed them accordingly. I then changed the font size of the question and added padding and margin to some components to separate them. Here is what I was left with:

I’m not much of a designer but I am happy with the way the project came out but if there’s something you don’t like, play around with the styling. Adjust the font sizes, font color, background colors or spacing between components. There’s a lot you can do to make your app unique. You can change the image of the raccoon to something else, maybe a bird, or change the color scheme. There are a lot of options online to find royalty free images and color schemes.

In the next article, we will continue to work with this project. We will use more built in components and style them. For now, make sure you understand what was done in this article and if there’s something that doesn’t make sense visit the React Native documentation, https://facebook.github.io/react-native/.