react-native – Fit Image in containing View, not the whole screen size

If you know the aspect ratio for example, if your image is square you can set either the height or the width to fill the container and get the other to be set by the aspectRatio property

Here is the style if you want the height be set automatically:

{
    width: '100%',
    height: undefined,
    aspectRatio: 1,
}

Note: height must be undefined

Edit (Based on @rob-art’s comment):
If your image is a different aspect ratio than the one you want to set in the style you can use resizeMode to control how the image should be displayed. Use resizeMode:'contain' to ensure your image is not cropped.
See documentation for more details