Android Universal Image Loader

compile 'com.nostra13.universalimageloader:universal-image-loader:1.9.4'

// DON'T COPY THIS CODE TO YOUR PROJECT! This is just example of ALL options using.
// See the sample project how to use ImageLoader correctly.
File cacheDir = StorageUtils.getCacheDirectory(context);
ImageLoaderConfiguration config = new ImageLoaderConfiguration.Builder(context)
        .memoryCacheExtraOptions(480, 800) // default = device screen dimensions
        .diskCacheExtraOptions(480, 800, null)
        .taskExecutor(...)
        .taskExecutorForCachedImages(...)
        .threadPoolSize(3) // default
        .threadPriority(Thread.NORM_PRIORITY - 2) // default
        .tasksProcessingOrder(QueueProcessingType.FIFO) // default
        .denyCacheImageMultipleSizesInMemory()
        .memoryCache(new LruMemoryCache(2 * 1024 * 1024))
        .memoryCacheSize(2 * 1024 * 1024)
        .memoryCacheSizePercentage(13) // default
        .diskCache(new UnlimitedDiscCache(cacheDir)) // default 也可以自定义缓存路径
        .diskCacheSize(50 * 1024 * 1024)
        .diskCacheFileCount(100)
        .diskCacheFileNameGenerator(new HashCodeFileNameGenerator()) // default
        .imageDownloader(new BaseImageDownloader(context)) // default
        .imageDecoder(new BaseImageDecoder()) // default
        .defaultDisplayImageOptions(DisplayImageOptions.createSimple()) // default
        .writeDebugLogs()
        .build();

	final Resources resources;
	final int maxImageWidthForMemoryCache;
	内存缓存图片的最大宽度
	final int maxImageHeightForMemoryCache;
	内存缓存图片的最大高度
	final int maxImageWidthForDiskCache;
	磁盘缓存图片的宽度
	final int maxImageHeightForDiskCache;
	磁盘缓存图片的高度
	final BitmapProcessor processorForDiskCache;
	磁盘缓存图片处理器
	final Executor taskExecutor;

	final Executor taskExecutorForCachedImages;
	缓存任务线程池
	final boolean customExecutor;

	final boolean customExecutorForCachedImages;
	自定义缓存线程池
	final int threadPoolSize;
	池里核心线程数
	final int threadPriority;
	线程优先级
	final QueueProcessingType tasksProcessingType;
	任务队列的类型：enum{LIFO、FIFO}
	final MemoryCache memoryCache;
	内存缓存
	final DiskCache diskCache;
	磁盘缓存
	final ImageDownloader downloader;
	图片下载器
	final ImageDecoder decoder;
	图片解析器
	final DisplayImageOptions defaultDisplayImageOptions;
    图片显示参数
	final ImageDownloader networkDeniedDownloader;
	图片下载器：禁止从网络加载
	final ImageDownloader slowNetworkDownloader;
	图片下载器：慢速网络加载

import android.annotation.TargetApi;
import android.app.Application;
import android.content.Context;
import android.os.Build;
import android.os.StrictMode;
import com.nostra13.universalimageloader.cache.disc.naming.Md5FileNameGenerator;
import com.nostra13.universalimageloader.core.ImageLoader;
import com.nostra13.universalimageloader.core.ImageLoaderConfiguration;
import com.nostra13.universalimageloader.core.assist.QueueProcessingType;

/**
 * @author Sergey Tarasevich (nostra13[at]gmail[dot]com)
 */
public class UILApplication extends Application {
	@TargetApi(Build.VERSION_CODES.GINGERBREAD)
	@SuppressWarnings("unused")
	@Override
	public void onCreate() {
		if (Constants.Config.DEVELOPER_MODE && Build.VERSION.SDK_INT >= Build.VERSION_CODES.GINGERBREAD) {
			StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder().detectAll().penaltyDialog().build());
			StrictMode.setVmPolicy(new StrictMode.VmPolicy.Builder().detectAll().penaltyDeath().build());
		}

		super.onCreate();

		initImageLoader(getApplicationContext());
	}

	public static void initImageLoader(Context context) {
		// This configuration tuning is custom. You can tune every option, you may tune some of them,
		// or you can create default configuration by
		//  ImageLoaderConfiguration.createDefault(this);
		// method.
		ImageLoaderConfiguration.Builder config = new ImageLoaderConfiguration.Builder(context);
		config.threadPriority(Thread.NORM_PRIORITY - 2);
		config.denyCacheImageMultipleSizesInMemory();
		config.diskCacheFileNameGenerator(new Md5FileNameGenerator());
		config.diskCacheSize(50 * 1024 * 1024); // 50 MiB
		config.tasksProcessingOrder(QueueProcessingType.LIFO);
		config.writeDebugLogs(); // Remove for release app

		// Initialize ImageLoader with configuration.
		ImageLoader.getInstance().init(config.build());
	}
}

//先得到单例实体imageLoader
ImageLoader imageLoader = ImageLoader.getInstance(); // Get singleton instance

// Load image, decode it to Bitmap and display Bitmap in ImageView (or any other view
//  which implements ImageAware interface)
//调用imageLoader.displayImage将imageUri对应的图片显示在imageView组件上
imageLoader.displayImage(imageUri, imageView);

// Load image, decode it to Bitmap and return Bitmap to callback
//监听图片加载，处理回调函数
imageLoader.loadImage(imageUri, new SimpleImageLoadingListener() {
    @Override
    public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage) {
        // Do whatever you want with Bitmap
    }
});

// Load image, decode it to Bitmap and return Bitmap synchronously
//加载图片并将其解码成Bitmap
Bitmap bmp = imageLoader.loadImageSync(imageUri);

// Load image, decode it to Bitmap and display Bitmap in ImageView (or any other view
//  which implements ImageAware interface)
imageLoader.displayImage(imageUri, imageView, options, new ImageLoadingListener() {
    @Override
    public void onLoadingStarted(String imageUri, View view) {
        ...
    }
    @Override
    public void onLoadingFailed(String imageUri, View view, FailReason failReason) {
        ...
    }
    @Override
    public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage) {
        ...
    }
    @Override
    public void onLoadingCancelled(String imageUri, View view) {
        ...
    }
}, new ImageLoadingProgressListener() {
    @Override
    public void onProgressUpdate(String imageUri, View view, int current, int total) {
        ...
    }
});
// Load image, decode it to Bitmap and return Bitmap to callback
ImageSize targetSize = new ImageSize(80, 50); // result Bitmap will be fit to this size
imageLoader.loadImage(imageUri, targetSize, options, new SimpleImageLoadingListener() {
    @Override
    public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage) {
        // Do whatever you want with Bitmap
    }
});
// Load image, decode it to Bitmap and return Bitmap synchronously
ImageSize targetSize = new ImageSize(80, 50); // result Bitmap will be fit to this size
Bitmap bmp = imageLoader.loadImageSync(imageUri, targetSize, options);

// DON'T COPY THIS CODE TO YOUR PROJECT! This is just example of ALL options using.
// See the sample project how to use ImageLoader correctly.
DisplayImageOptions options = new DisplayImageOptions.Builder()
        .showImageOnLoading(R.drawable.ic_stub) // resource or drawable
        .showImageForEmptyUri(R.drawable.ic_empty) // resource or drawable
        .showImageOnFail(R.drawable.ic_error) // resource or drawable
        .resetViewBeforeLoading(false)  // default
        .delayBeforeLoading(1000)
        .cacheInMemory(false) // default
        .cacheOnDisk(false) // default
        .preProcessor(...)
        .postProcessor(...)
        .extraForDownloader(...)
        .considerExifParams(false) // default
        .imageScaleType(ImageScaleType.IN_SAMPLE_POWER_OF_2) // default
        .bitmapConfig(Bitmap.Config.ARGB_8888) // default
        .decodingOptions(...)
        .displayer(new SimpleBitmapDisplayer()) // default
        .handler(new Handler()) // default
        .build();

	private final int imageResOnLoading;
	正在加载时显示的图片资源		id
	private final int imageResForEmptyUri;
	图片uri为空时显示的图片		id
	private final int imageResOnFail;		
	图片加载失败显示的图片		id
	private final Drawable imageOnLoading;
	正在加载时显示的图片资源		drawable
	private final Drawable imageForEmptyUri;
	图片uri为空时显示的图片		drawable
	private final Drawable imageOnFail;
	图片加载失败显示的图片		drawable
	private final boolean resetViewBeforeLoading;
	加载前是否重置view
	private final boolean cacheInMemory;
	是否启用内存缓存
	private final boolean cacheOnDisk;
	是否启用磁盘缓存
	private final ImageScaleType imageScaleType;
	图片缩放类型
	private final Options decodingOptions;
	BitmapFactory用到的options
	private final int delayBeforeLoading;
	延迟多久加载
	private final boolean considerExifParams;
	exif参数是否可用
	private final Object extraForDownloader;
	额外的下载对象
	private final BitmapProcessor preProcessor;
	bitmap加载前的处理
	private final BitmapProcessor postProcessor;
	bitmap加载时的处理
	private final BitmapDisplayer displayer;
	bitmap显示
	private final Handler handler;
	private final boolean isSyncLoading;
	是否同步加载图片(一个接一个的加载)

"http://site.com/image.png" // from Web
"file:///mnt/sdcard/image.png" // from SD card
"file:///mnt/sdcard/video.mp4" // from SD card (video thumbnail)
"content://media/external/images/media/13" // from content provider
"content://media/external/video/media/13" // from content provider (video thumbnail)
"assets://image.png" // from assets
"drawable://" + R.drawable.img // from drawables (non-9patch images)

// Create default options which will be used for every
//  displayImage(...) call if no options will be passed to this method
DisplayImageOptions defaultOptions = new DisplayImageOptions.Builder()
        ...
        .cacheInMemory(true)
        .cacheOnDisk(true)
        ...
        .build();
ImageLoaderConfiguration config = new ImageLoaderConfiguration.Builder(getApplicationContext())
        ...
        .defaultDisplayImageOptions(defaultOptions)
        ...
        .build();
ImageLoader.getInstance().init(config); // Do it on Application start

// Then later, when you want to display image
ImageLoader.getInstance().displayImage(imageUrl, imageView); // Default options will be used

DisplayImageOptions options = new DisplayImageOptions.Builder()
        ...
        .cacheInMemory(true)
        .cacheOnDisk(true)
        ...
        .build();
ImageLoader.getInstance().displayImage(imageUrl, imageView, options); // Incoming options will be used