BackHandler React Native

Pattern

The pattern for using the BackHandler module in React Native involves the following steps :

• Import the BackHandler module:

  Start by importing the BackHandler module from the React Native core library :

• Add an Event Listener:

  Next, add an event listener to capture the back button press event. This event listener will define the custom logic to be executed when the back button is pressed. The event listener is typically added in the componentDidMount lifecycle method for class components or within the useEffect hook for function components.

• Define the Back Button Handling Logic :

  In the event listener, define the custom logic to be executed when the back button is pressed. This can include actions like navigating to the previous screen, showing a confirmation dialog before exiting the app, or any other desired behavior.

• Remove the Event Listener (if necessary) :

  If you no longer need the event listener, make sure to remove it to avoid memory leaks. This is typically done in the componentWillUnmount lifecycle method for class components or by returning a cleanup function from the useEffect hook for function components.

  By following this pattern, you can effectively use the BackHandler module in React Native to handle back button events and define the desired behavior when the back button is pressed. Remember to define the appropriate handling logic and ensure that the event listener is properly added and removed to maintain the integrity of your application's navigation flow.

Example

Here's an example of using the BackHandler module in both a function component and a class component.

Function Component

Class Component

Usage with React Navigation

React Navigation is a popular navigation library for React Native applications. To integrate the BackHandler module with React Navigation, you can follow the steps below :

• Import the required modules:

  In your component file, import the necessary modules from React Navigation and the BackHandler module :

• Define the back button handling logic:

  Inside your component, define the logic to handle the back button press. This logic can include actions like navigating to the previous screen, showing a confirmation dialog before exiting the app, or any other desired behavior.

• Use the useFocusEffect hook :

  Wrap the back button handling logic inside the useFocusEffect hook provided by React Navigation. This hook allows you to run effects when the screen comes into focus and clean them up when it goes out of focus.

• Complete the component:

  Finish the component implementation, including the rendering logic and any other functionality you require.

By using the useFocusEffect hook from React Navigation, you can add the necessary event listener for the back button and remove it when the screen loses focus. This approach ensures that the back button handling is specific to the currently focused screen and avoids conflicts or unexpected behavior across different screens in your navigation stack.

Make sure to import the necessary modules, define the back button handling logic, and use the useFocusEffect hook to integrate the BackHandler module with React Navigation effectively. This enables you to control the back button behavior within your React Native app's navigation flow.

Backhandler hook

The BackHandler React Native provides a hook called useBackHandler (introduced in React Native version 0.62) that simplifies the usage of the BackHandler module in function components. The useBackHandler hook allows you to define the back button action directly within the component function.

Methods

addEventListener(eventName, handler):

The addEventListener() method is used to register an event listener for a specific event. In the case of the BackHandler module, the event is typically 'hardwareBackPress', which corresponds to the back button press event on Android devices or the hardware back button on some physical devices.

Syntax:

This method returns an instance of BackHandlerSubscription, which can be stored in a variable (e.g., backHandler). This subscription allows you to later remove the event listener using the removeEventListener() method.

Example:

exitApp():

The exitApp() method is used to exit the application programmatically. When called, this method terminates the app and returns the user to the operating system or home screen. It effectively simulates the behavior of the user pressing the home button or navigating away from the app.

Syntax:

Example:

removeEventListener(eventName, handler):

The removeEventListener() method is used to remove a previously registered event listener. It takes the event name and the handler function as arguments. The event listener will no longer respond to the specified event after it is removed.

Syntax:

Example:

By using these methods provided by the BackHandler module, you can add event listeners for the back button press event, exit the app programmatically, and remove event listeners when they are no longer needed. This allows you to customize the back button behavior and control the navigation flow in your React Native application.