Custom useKeyboardAvoiding Hook: Adjusting View Translation Based on Keyboard Height in Expo/React Native

In the realm of mobile application development, user experience reigns supreme. One crucial aspect of a seamless and intuitive user experience is ensuring that the app's layout remains uncluttered and accessible, even when the virtual keyboard appears, obstructing the user's view. This is where the concept of "keyboard avoidance" comes into play. React Native, with its Expo framework, provides a built-in solution for this challenge – the `KeyboardAvoidingView` component. However, in certain scenarios, the default behavior of `KeyboardAvoidingView` may not be sufficient, requiring a more tailored approach. This article delves into creating a custom `useKeyboardAvoiding` hook in React Native/Expo that allows for fine-grained control over view translation based on keyboard height.

Understanding Keyboard Avoidance

The fundamental principle behind keyboard avoidance is to dynamically adjust the position of elements within the app's UI when the keyboard appears, preventing the user's input field from being obscured. This adjustment is typically achieved by shifting the view upwards, effectively "making room" for the keyboard. React Native's `KeyboardAvoidingView` component handles this automatically, relying on various strategies like:

Content Insets: The `KeyboardAvoidingView` leverages content insets provided by the underlying platform (iOS and Android) to determine the area occupied by the keyboard. This allows the view to adjust its position accordingly.
Padding: The component can also use padding around its content to push it away from the keyboard.
ScrollView Scrolling: For views that are scrollable, `KeyboardAvoidingView` can scroll the view upwards to bring the input field into view.

The Limitations of `KeyboardAvoidingView`

While `KeyboardAvoidingView` is generally a powerful tool, it may not always meet specific requirements, especially in scenarios where the default behavior needs to be customized. Here are some scenarios where a custom approach may be necessary:

Complex Layouts: If the app's UI layout is intricate, with overlapping or nested views, `KeyboardAvoidingView` might not be able to determine the appropriate adjustment accurately.
Specific Animation Requirements: When custom animations are desired during the keyboard appearance/disappearance, the default behavior might not provide the desired level of control.
Performance Optimization: In cases where performance is a primary concern, developers may want to optimize the keyboard avoidance mechanism by implementing custom logic.

Creating a Custom `useKeyboardAvoiding` Hook

To address the limitations mentioned above, we can create a custom `useKeyboardAvoiding` hook that provides greater flexibility and customization options. The following code demonstrates the implementation of such a hook:

import React, { useState, useEffect } from 'react';
import { Dimensions, Keyboard, Animated } from 'react-native';

const useKeyboardAvoiding = () =&gt; {
  const [keyboardHeight, setKeyboardHeight] = useState(0);
  const [keyboardShown, setKeyboardShown] = useState(false);
  const [keyboardAnimation, setKeyboardAnimation] = useState(new Animated.Value(0));

  useEffect(() =&gt; {
    const keyboardDidShowListener = Keyboard.addListener('keyboardDidShow', (event) =&gt; {
      setKeyboardHeight(event.endCoordinates.height);
      setKeyboardShown(true);
      Animated.timing(keyboardAnimation, {
        toValue: event.endCoordinates.height,
        duration: 250,
        useNativeDriver: false, // Important for smoother animations
      }).start();
    });

    const keyboardDidHideListener = Keyboard.addListener('keyboardDidHide', () =&gt; {
      setKeyboardHeight(0);
      setKeyboardShown(false);
      Animated.timing(keyboardAnimation, {
        toValue: 0,
        duration: 250,
        useNativeDriver: false, // Important for smoother animations
      }).start();
    });

    return () =&gt; {
      keyboardDidShowListener.remove();
      keyboardDidHideListener.remove();
    };
  }, []);

  return { keyboardHeight, keyboardShown, keyboardAnimation };
};

export default useKeyboardAvoiding;

Explanation:

State Management: The hook uses React's `useState` to manage the following state variables:
- `keyboardHeight`: Stores the current height of the keyboard.
- `keyboardShown`: A boolean indicating whether the keyboard is currently visible.
- `keyboardAnimation`: An Animated value used for controlling the animation of the view's translation.
Event Listeners: The `useEffect` hook subscribes to keyboard events:
- `keyboardDidShow`: This event is triggered when the keyboard appears. The hook updates the `keyboardHeight` and `keyboardShown` states, and starts an animation to adjust the view's position.
- `keyboardDidHide`: This event is triggered when the keyboard disappears. The hook resets the `keyboardHeight` and `keyboardShown` states, and starts an animation to restore the view's position.
Animated Translation: The hook uses `Animated.timing` to create a smooth animation for the view's translation. The animation's duration and `useNativeDriver` configuration can be adjusted to achieve the desired smoothness.
Return Value: The hook returns an object containing the state variables `keyboardHeight`, `keyboardShown`, and `keyboardAnimation`, which can be used by the component to adjust its layout.

Integrating the Custom Hook

Now that the `useKeyboardAvoiding` hook is defined, you can integrate it into your React Native components to implement custom keyboard avoidance behavior. Here's an example:

import React from 'react';
import { View, StyleSheet, Animated } from 'react-native';
import useKeyboardAvoiding from './useKeyboardAvoiding'; // Assuming the hook is in a separate file

const MyComponent = () =&gt; {
  const { keyboardHeight, keyboardAnimation } = useKeyboardAvoiding();

  return (
<view style="{styles.container}">
 <animated.view [{="" ]}="" keyboardanimation="" style="{[" styles.content,="" transform:="" translatey:="" {="" },="" }],="">
  {/* Your content here */}
 </animated.view>
</view>
);
};

const styles = StyleSheet.create({
  container: {
    flex: 1,
  },
  content: {
    padding: 20,
    backgroundColor: 'white',
  },
});

export default MyComponent;

Explanation:

Import: Import the `useKeyboardAvoiding` hook from its file.
Usage: Call the hook within the component, extracting the `keyboardHeight` and `keyboardAnimation` state variables.
Animated View: Wrap the content that needs to be adjusted by the keyboard in an `Animated.View`. Apply the `translateY` transform to this view, using the `keyboardAnimation` value to dynamically shift its position.

Customizing the Behavior

The custom hook provides a foundation for implementing various keyboard avoidance strategies. You can modify the logic within the hook to fine-tune the behavior based on your specific needs. Here are some customization options:

Animation Duration: Adjust the `duration` property in the `Animated.timing` function to control the speed of the animation.
Easing Function: Use different easing functions to modify the animation's curve (e.g., `Animated.Easing.easeIn`, `Animated.Easing.easeOut`, `Animated.Easing.elastic`).
Keyboard Offset: Introduce an offset to the `keyboardHeight` before applying it to the `translateY` transform. This can be useful if you want to adjust the view's position slightly above or below the actual keyboard height.
Conditional Rendering: Based on the `keyboardShown` state, you can conditionally render different content or styles depending on whether the keyboard is visible.

Example: Handling Keyboard Input in a Form

Let's illustrate a practical example of using the custom `useKeyboardAvoiding` hook to handle keyboard input within a form. In this example, we'll have a form with an input field and a button. When the keyboard appears, the input field will be moved up to avoid being hidden behind the keyboard, providing a seamless user experience.

import React, { useState } from 'react';
import { View, StyleSheet, TextInput, Button, Animated } from 'react-native';
import useKeyboardAvoiding from './useKeyboardAvoiding';

const MyForm = () =&gt; {
  const [inputText, setInputText] = useState('');
  const { keyboardHeight, keyboardAnimation } = useKeyboardAvoiding();

  const handleInputChange = (text) =&gt; {
    setInputText(text);
  };

  return (
<view style="{styles.container}">
 <animated.view [{="" ]}="" keyboardanimation="" style="{[" styles.content,="" transform:="" translatey:="" {="" },="" }],="">
  <textinput onchangetext="{handleInputChange}" placeholder="Enter your text" style="{styles.input}" value="{inputText}">
  </textinput>
  <button =="" onpress="{()" title="Submit">
   console.log('Form submitted!')} /&gt;
  </button>
 </animated.view>
</view>
);
};

const styles = StyleSheet.create({
  container: {
    flex: 1,
  },
  content: {
    padding: 20,
    backgroundColor: 'white',
  },
  input: {
    borderWidth: 1,
    borderColor: 'gray',
    padding: 10,
    marginBottom: 10,
  },
});

export default MyForm;

Explanation:

Form Elements: The component includes a `TextInput` for user input and a `Button` to submit the form.
Keyboard Avoidance: The `Animated.View` wraps the form elements and adjusts its `translateY` based on `keyboardAnimation`, ensuring that the input field remains visible even when the keyboard is up.
State Management: The `inputText` state variable stores the user's input, and the `handleInputChange` function updates it when the input field's value changes.

Conclusion

Creating a custom `useKeyboardAvoiding` hook in React Native/Expo empowers developers with finer control over view translation based on keyboard height. This approach offers flexibility beyond the default `KeyboardAvoidingView` component, allowing for intricate animations, complex layouts, and performance optimization. By understanding the core concepts of keyboard avoidance and leveraging custom hooks, developers can create a more seamless and engaging user experience for their mobile applications.

Remember, the custom hook presented in this article is a starting point. You can further customize it by adding more state variables, incorporating different animation styles, and implementing specific behaviors to address unique requirements within your project.