How can i just download image with universal-image-loader

问题

as far as I know, universal-image-loader provide 2 kinds of methods to display images. imageLoader.loadImage and imageLoader.displayImage. But those 2 methods must bind to UI element to display. Can I just download files for cache in a thread (for future display). I don't need to display those image right now.

回答1:

Can I just download files for cache in a thread (for future display). I don't need to display those image right now.

You can download files using Executor or creating a thread. You don't need to use universal imageloader.

http://developer.android.com/reference/java/util/concurrent/Executor.html.

You can also use a DownloadManager and save the file in sdcard. You can retrieve the same for later use.

http://oodlestechnologies.com/blogs/Downloading-and-Retrieving-Files-on-SD-card-in-Android-using-Android-SDK-in-Eclipse

To cache bitmaps you can write the images to a folder in sdcard.

Caching bitmaps

http://developer.android.com/training/displaying-bitmaps/cache-bitmap.html.

You cache bitmaps in memory or disk. The link has details regarding the topic.

You basically use UIL ofr displaying images in listview or grdiview. To use UIL in listview or gridview you can do as below.

https://github.com/nostra13/Android-Universal-Image-Loader. It is based on Lazy List(works on same principle). But it has lot of other configurations. You can display a error image if downlaod failed. Can display images with rounded corners. Can cache on disc or memory. Can compress image.

In your custom adapter constructor

 File cacheDir = StorageUtils.getOwnCacheDirectory(a, "your folder");

 // Get singletone instance of ImageLoader
 imageLoader = ImageLoader.getInstance();
 // Create configuration for ImageLoader (all options are optional)
 ImageLoaderConfiguration config = new ImageLoaderConfiguration.Builder(a)
      // You can pass your own memory cache implementation
     .discCache(new UnlimitedDiscCache(cacheDir)) // You can pass your own disc cache implementation
     .discCacheFileNameGenerator(new HashCodeFileNameGenerator())
     .enableLogging()
     .build();
 // Initialize ImageLoader with created configuration. Do it once.
 imageLoader.init(config);
 options = new DisplayImageOptions.Builder()
 .showStubImage(R.drawable.stub_id)//display stub image
 .cacheInMemory()
 .cacheOnDisc()
 .displayer(new RoundedBitmapDisplayer(20))
 .build();

In your getView()

 ImageView image=(ImageView)vi.findViewById(R.id.imageview); 
 imageLoader.displayImage(imageurl, image,options);//provide imageurl, imageview and options

You can configure with other options to suit your needs.

Along with lazy loading/Universal Image Loader you can view holder for smooth scrolling and performance. http://developer.android.com/training/improving-layouts/smooth-scrolling.html.

回答2:

You can still use UIL. Based on the displayOptions used below the images would be cached.

Refer here - https://github.com/nostra13/Android-Universal-Image-Loader

// Load image, decode it to Bitmap and return Bitmap to callback

imageLoader.loadImage(imageUri, displayOptions, new SimpleImageLoadingListener() {
    @Override
    public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage) {
        // Do whatever you want with Bitmap
    }
});

回答3:

Theres loadImage(String uri, ImageLoadingListener listener), I think you can call it with null for the listener if you don't need one.

回答4:

Adding to @Robin Srivastava's answer:

You must also instantiate the ImageLoader context, for example: imageLoader = ImageLoader.getInstance(); before you can use the loadImage method. The displayOptions parameter is also optional so you can exclude that if need be.

来源：https://stackoverflow.com/questions/16016619/how-can-i-just-download-image-with-universal-image-loader

标签

android

universal-image-loader