When developing Flutter applications, displaying images fetched from the web is a common task. You may find yourself using the Image.network widget to integrate online images into your app. However, sometimes developers face challenges when attempting to resize these images. For instance, you might have tried changing the height of the image with syntax like this: Image.network("image_url", height: 45) and noticed that it didn't work as expected. In this article, we'll explore the reasons behind this issue and provide you with practical solutions to resize images effectively.

Understanding the Image.network Widget

Image.networkheightwidthImage

Why the Size Change Might Not Work

Image.networkheight
  1. Aspect Ratio: By default, Flutter maintains the aspect ratio of the image. If you set only the height, the width gets automatically computed to preserve the original proportions. Conversely, if the image’s original width is less than 45 pixels, it might distort or display incorrectly.
  2. Parent Constraints: The size of the widget can also be affected by its parent widget's constraints. If the parent container is too small, it might limit the image's display size even if you specify height and width.
  3. Fading to Container Size: The Image widget could also adopt limitations based on the box constraints of its parent widget. If the containing widget restricts size, then your specified dimensions won’t take effect.

How to Resize an Image Using Image.network

Image.network

Method 1: Using Height and Width Parameters

Image.network
Image.network(
  "image_url",
  height: 45,
  width: 45,
  fit: BoxFit.cover,
)

In this example, both the height and width are specified as 45 pixels, and we also use the fit property to ensure the image scales properly within its size constraints. The BoxFit.cover option helps to fill the box while maintaining the image's aspect ratio.

Method 2: Wrapping Image.network in a Container

Image.networkContainer
Container(
  height: 45,
  width: 45,
  child: Image.network(
    "image_url",
    fit: BoxFit.cover,
  ),
)

This method can help ensure that the image scales precisely to the dimensions set by the container, providing you with better results.

Best Practices when Displaying Network Images

  • Caching: Consider using the cached_network_image package to cache images. Cached images load faster on subsequent displays and reduce network usage.
  • Error Handling: Implement error handling using the errorBuilder property to provide a fallback when an image fails to load. For example:
Image.network(
  "image_url",
  errorBuilder: (context, error, stackTrace) {
    return Icon(Icons.error);
  },
)

This will display an error icon if the image cannot be fetched.

  • Image Placeholders: While the image is loading, you might want to display a placeholder, providing a better user experience. You can do this by using the loadingBuilder parameter:
Image.network(
  "image_url",
  loadingBuilder: (context, child, loadingProgress) {
    if (loadingProgress == null) return child;
    return Center(child: CircularProgressIndicator());
  },
)

Frequently Asked Questions

Can I change only the height without affecting the width?



What happens if I don’t set any height or width?



Is using BoxFit important?

BoxFitImage.network