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How to Use Universal Image Loader Library in Android?

Universal Image Loader (UIL) is a powerful, flexible, and customizable instrument for image loading, caching, and displaying. It's particularly useful for Android projects where smooth scrolling and fast image loading are essential.

Here's how to use Universal Image Loader in your Android project:

1. Add the Dependency:

First, add the UIL library dependency to your app's build.gradle file:

implementation 'com.nostra13.universalimageloader:universal-image-loader:1.9.5'

Then, sync your project.

2. Configuration:

Before using UIL, it should be configured. The configuration is typically done in the Application class:

val config = ImageLoaderConfiguration.Builder(this)
    .threadPriority(Thread.NORM_PRIORITY - 2)
    .denyCacheImageMultipleSizesInMemory()
    .diskCacheFileNameGenerator(HashCodeFileNameGenerator())
    .tasksProcessingOrder(QueueProcessingType.LIFO)
    .build()

ImageLoader.getInstance().init(config)

This is a basic configuration. UIL offers numerous options to fit specific needs.

3. Basic Usage:

To display an image from a URL into an ImageView:

ImageLoader.getInstance().displayImage("http://your.image.url.here", imageView)

4. Display Options:

You can configure display options to provide placeholders, error images, and more:

val options = DisplayImageOptions.Builder()
    .showImageOnLoading(R.drawable.placeholder) 
    .showImageForEmptyUri(R.drawable.empty_image)
    .showImageOnFail(R.drawable.error_image)
    .cacheInMemory(true)
    .cacheOnDisk(true)
    .build()

ImageLoader.getInstance().displayImage("http://your.image.url.here", imageView, options)

5. Loading Images:

If you want to load an image without displaying it (for caching purposes, for example):

ImageLoader.getInstance().loadImage("http://your.image.url.here", object : SimpleImageLoadingListener() {
    override fun onLoadingComplete(imageUri: String?, view: View?, loadedImage: Bitmap?) {
        // Handle the loaded bitmap here
    }
})

6. Caching:

UIL provides robust caching mechanisms:

Memory Cache: By default, UIL caches images in memory.
Disk Cache: UIL also supports caching on the device's file system. This can be enabled in the configuration.

7. Listeners:

You can use listeners to get callbacks for various events:

ImageLoader.getInstance().displayImage("http://your.image.url.here", imageView, object : ImageLoadingListener {
    override fun onLoadingStarted(imageUri: String?, view: View?) {
        // Loading started
    }

    override fun onLoadingFailed(imageUri: String?, view: View?, failReason: FailReason?) {
        // Loading failed
    }

    override fun onLoadingComplete(imageUri: String?, view: View?, loadedImage: Bitmap?) {
        // Loading completed
    }

    override fun onLoadingCancelled(imageUri: String?, view: View?) {
        // Loading cancelled
    }
})

8. Pause And Resume:

When scrolling a list or a grid of images, it can be useful to pause image loading to achieve smoother scrolling:

ImageLoader.getInstance().pause()
ImageLoader.getInstance().resume()

9. Clearing Cache:

To clear memory and/or disk cache:

ImageLoader.getInstance().clearMemoryCache()
ImageLoader.getInstance().clearDiskCache()

While UIL is a great tool, it's worth noting that some newer libraries like Glide or Picasso offer similar capabilities and might be more suitable for certain use cases. Consider evaluating your project's needs and the features of each library before deciding.

How to integrate Universal Image Loader library for image loading in Android:
To integrate Universal Image Loader in your Android project, add the following dependency to your app's build.gradle file:
```
implementation 'com.nostra13.universalimageloader:universal-image-loader:1.9.5'
```
After adding the dependency, you can use Universal Image Loader to load images in your app.

Android Universal Image Loader example code:

In your Android code, use Universal Image Loader to load an image into an ImageView:

ImageView imageView = findViewById(R.id.imageView);

String imageUrl = "https://example.com/image.jpg";

ImageLoader.getInstance().displayImage(imageUrl, imageView);

Handling image loading and caching with Universal Image Loader in Android:

Universal Image Loader provides comprehensive options for handling image loading and caching. You can customize the loading process, configure caching strategies, and handle image loading events.

// Load image with placeholder and error handling
DisplayImageOptions options = new DisplayImageOptions.Builder()
        .showImageOnLoading(R.drawable.placeholder)
        .showImageForEmptyUri(R.drawable.placeholder)
        .showImageOnFail(R.drawable.error_image)
        .cacheInMemory(true)
        .cacheOnDisk(true)
        .build();

ImageLoader.getInstance().displayImage(imageUrl, imageView, options);

Universal Image Loader vs Picasso vs Glide: Image loading libraries comparison:
Universal Image Loader, Picasso, and Glide are popular image loading libraries for Android. Each has its own strengths and considerations. Universal Image Loader is known for its flexibility and customization options. Picasso is lauded for its simplicity and ease of use, while Glide excels in handling large and animated images efficiently.
```
// Example using Picasso
Picasso.get()
       .load(imageUrl)
       .placeholder(R.drawable.placeholder)
       .error(R.drawable.error_image)
       .into(imageView);

// Example using Glide
Glide.with(context)
     .load(imageUrl)
     .placeholder(R.drawable.placeholder)
     .error(R.drawable.error_image)
     .into(imageView);
```
Consider factors such as customization, performance, and specific features required for your project when choosing between these libraries.