What is the reason for the failure of RecyclerView to load network images and how to solve it?

Android RecyclerView loading network image problems and solutions

When loading network pictures using RecyclerView, the pictures often fail to display. This article analyzes the causes of this problem and provides multiple solutions.

Problem description: The developer uses RecyclerView to display the list of images obtained from the server, but the images cannot be displayed. The layout_height property of ImageView is set to wrap_content . After manually setting the fixed height, the image can be displayed normally.

Problem analysis: The root cause of the problem lies in layout_height property of the ImageView is set to wrap_content . Because network image loading takes time, RecyclerView cannot obtain the actual height of the image when measuring layout, resulting in the image height being unable to be determined, so the image cannot be displayed. wrap_content can only adapt to the height according to the image size after the image is loaded.

Solution:

The following methods can effectively solve this problem:

Method 1: Set a fixed height

The most direct way is to set a fixed height in the ImageView layout file, such as android:layout_height="200dp" . This ensures that the ImageView has a certain height before the image is loaded. However, this method will affect the aesthetics of the layout, especially when the proportion of the picture is large, it may lead to the picture deformation.

Method 2: Use placeholders

Use Glide and other pictures to load the library and set the placeholder picture. Display placeholders before the image is loaded to avoid blank areas and improve user experience. For example:

 Glide.with(context)
    .load(imageUrl)
    .placeholder(R.drawable.placeholder) // placeholder.into(imageView);

Method 3: Dynamically set the ImageView height

A better solution is to dynamically set the height of the ImageView based on the image aspect ratio completed by loading. This requires the use of Glide's RequestListener . After the image is loaded, the image width and height are obtained through resource.getIntrinsicWidth() and resource.getIntrinsicHeight() , calculate the ImageView height and set it. The sample code is as follows:

 Glide.with(context)
    .load(imageUrl)
    .listener(new RequestListener<drawable> () {
        @Override
        public boolean onLoadFailed(@Nullable GlideException e, Object model, Target<drawable> target, boolean isFirstResource) {
            return false;
        }

        @Override
        public boolean onResourceReady(Drawable resource, Object model, Target<drawable> target, DataSource dataSource, boolean isFirstResource) {
            int width = imageView.getWidth();
            float aspectRatio = (float) resource.getIntrinsicWidth() / resource.getIntrinsicHeight();
            int height = Math.round(width/aspectRatio);
            imageView.setLayoutParams(new ViewGroup.LayoutParams(width, height));
            return false;
        }
    })
    .into(imageView);</drawable></drawable></drawable>

Which method to choose depends on the specific requirements. Method 3 Although the code is complex, it can ensure the correct display ratio of the picture and provide the best user experience. Method 1 and Method 2 are simpler and easier to use, but there may be some limitations.

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