Building a Custom Dropdown Component for React Native
When it comes to creating dropdowns in React Native, there are plenty of third-party libraries available. However, most of these libraries are actually spinners, which can look quite different from the dropdowns we’re used to in web development. In this article, we’ll create a basic select form field that looks and feels like a traditional dropdown, working seamlessly on both Android and iOS devices.
Getting Started
To begin, I created a new project using create-react-native-app and added the react-native-elements library to simplify the process of adding an icon to our dropdown. You can find the GitHub repo and Expo Snack for this project at the links below.
The Dropdown Component
Our dropdown component starts with a simple TouchableOpacity that toggles the visibility of the dropdown. The dropdown element itself has an absolute position, allowing it to open over the rest of the form. We’ll also add a state variable to track the visibility of the dropdown.
Creating the Real Dropdown
To make our dropdown functional, we need to add a few more props: one for the data that will populate the dropdown items, and a function to fire when an item is selected. We’ll use a FlatList to create the list of items, which provides built-in functionality and performance benefits.
Using a Modal for the Dropdown
To get the desired functionality, we’ll use a Modal to render the list of items. We’ll set the transparent prop on the Modal, allowing users to click outside of the dropdown to close it. Inside the Modal, we’ll add a TouchableOpacity to cover the entire overlay, and a View to wrap the FlatList and set its styles.
Modifying the Visibility Toggle Function
To position the dropdown correctly, we need to measure the location of the button on the screen and set the top value of the dropdown accordingly. We’ll add a few constants to achieve this.
Rendering Items
The renderItem prop of the FlatList returns the component for each item. We’ll create a simple function to render the label and handle item presses. When an item is pressed, we’ll update the selected item state variable, replace the button label, and hide the dropdown.
The Final Result
With our dropdown component complete, we can now use it in our App.tsx file. We’ll add a state variable for the selected item, some sample data, and a Text element to display the selected item. The result is a fully functional dropdown component that works seamlessly on both Android and iOS devices.
Next Steps
Our dropdown component is now functional, but there’s still room for improvement. You can add better styles, more features, and even replace the external library with a self-contained component. Feel free to fork the GitHub repo and add your own features!