Android开发笔记（七十七）图片缓存算法

import java.io.File;
import java.lang.ref.WeakReference;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadPoolExecutor;

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.os.Environment;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.animation.AlphaAnimation;
import android.widget.ImageView;

public class ImageCache {
	private final static String TAG = "ImageCache";
	//内存中的图片缓存
	private HashMap<String, Bitmap> mImageMap = new HashMap<String, Bitmap>();
	//uri与视图控件的映射关系
	private HashMap<String, ImageView> mViewMap = new HashMap<String, ImageView>();
	//缓存队列，采用FIFO先进先出策略，需操作队列首尾两端，故采用双端队列
	private LinkedList<String> mUriList = new LinkedList<String>();
	
	private ImageCacheConfig mConfig;
	private String mDir = "";
	private ThreadPoolExecutor mPool;
	private static Handler mMyHandler;
	
	private static ImageCache mCache = null;
	private static Context mContext;
	
	public static ImageCache getInstance(Context context) {
		if (mCache == null) {
			mCache = new ImageCache();
			mCache.mContext = context;
		}
		return mCache;
	}
	
	public ImageCache initConfig(ImageCacheConfig config) {
		mCache.mConfig = config;
		mCache.mDir = mCache.mConfig.mDir;
		if (mCache.mDir==null || mCache.mDir.length()<=0) {
			mCache.mDir = Environment.getExternalStorageDirectory() + "/image_cache";
		}
		Log.d(TAG, "mDir="+mCache.mDir);
		//若目录不存在，则先创建新目录
		File dir = new File(mCache.mDir);
		if (dir.exists() != true) {
			dir.mkdirs();
		}
		mCache.mPool = (ThreadPoolExecutor) Executors.newFixedThreadPool(mCache.mConfig.mThreadCount);
		mCache.mMyHandler = new MyHandler((Activity)mCache.mContext);
		return mCache;
	}
	
	public void show(String uri, ImageView iv) {
		if (mConfig.mBeginImage != 0) {
			iv.setImageResource(mConfig.mBeginImage);
		}
		mViewMap.put(uri, iv);
		if (mImageMap.containsKey(uri) == true) {
			mCache.render(uri, mImageMap.get(uri));
		} else {
			String path = getFilePath(uri);
			if ((new File(path)).exists() == true) {
				Bitmap bitmap = ImageUtil.openBitmap(path);
				if (bitmap != null) {
					mCache.render(uri, bitmap);
				} else {
					mPool.execute(new MyRunnable(uri));
				}
			} else {
				mPool.execute(new MyRunnable(uri));
			}
		}
	}
	
	private String getFilePath(String uri) {
		String file_path = String.format("%s/%d.jpg", mDir, uri.hashCode());
		return file_path;
	}
	
	private static class MyHandler extends Handler {
		public static WeakReference<Activity> mActivity;

		public MyHandler(Activity activity) {
			mActivity = new WeakReference<Activity>(activity);
		}

		@Override
		public void handleMessage(Message msg) {
			Activity act = mActivity.get();
			if (act != null) {
				ImageData data = (ImageData) (msg.obj);
				if (data!=null && data.bitmap!=null) {
					mCache.render(data.uri, data.bitmap);
				} else {
					mCache.showError(data.uri);
				}
			}
		}
	}

	private class MyRunnable implements Runnable {
		private String mUri;
		public MyRunnable(String uri) {
			mUri = uri;
		}
		
		@Override
		public void run() {
			Activity act = MyHandler.mActivity.get();
			if (act != null) {
				Bitmap bitmap = ImageHttp.getImage(mUri);
				if (bitmap != null) {
					if (mConfig.mSize != null) {
						bitmap = Bitmap.createScaledBitmap(bitmap, mConfig.mSize.x, mConfig.mSize.y, false);
					}
					ImageUtil.saveBitmap(getFilePath(mUri), bitmap);
				}
				ImageData data = new ImageData(mUri, bitmap);
				Message msg = mMyHandler.obtainMessage();
				msg.obj = data;
				mMyHandler.sendMessage(msg);
			}
		}
	};

	private void render(String uri, Bitmap bitmap) {
		ImageView iv = mViewMap.get(uri);
		if (mConfig.mFadeInterval <= 0) {
			iv.setImageBitmap(bitmap);
		} else {
			//内存中已有图片的就直接显示，不再展示淡入淡出动画
			if (mImageMap.containsKey(uri) == true) {
				iv.setImageBitmap(bitmap);
			} else {
				iv.setAlpha(0.0f);
				AlphaAnimation alphaAnimation = new AlphaAnimation(0.0f, 1.0f);
				alphaAnimation.setDuration(mConfig.mFadeInterval);
				alphaAnimation.setFillAfter(true);
				iv.setImageBitmap(bitmap);
				iv.setAlpha(1.0f);
				iv.setAnimation(alphaAnimation);
				alphaAnimation.start();
				mCache.refreshList(uri, bitmap);
			}
		}
	}
	
	private synchronized void refreshList(String uri, Bitmap bitmap) {
		if (mUriList.size() >= mConfig.mMemoryFileCount) {
			String out_uri = mUriList.pollFirst();
			mImageMap.remove(out_uri);
		}
		mImageMap.put(uri, bitmap);
		mUriList.addLast(uri);
	}
	
	private void showError(String uri) {
		ImageView iv = mViewMap.get(uri);
		if (mConfig.mErrorImage != 0) {
			iv.setImageResource(mConfig.mErrorImage);
		}
	}
	
	public void clear() {
		for (Map.Entry<String, Bitmap> item_map : mImageMap.entrySet()) {
			Bitmap bitmap = item_map.getValue();
			bitmap.recycle();
		}
		mCache = null;
	}

}

			ImageCacheConfig config = new ImageCacheConfig.Builder()
				.setBeginImage(R.drawable.bliss)
				.setErrorImage(R.drawable.error)
				.setFadeInterval(2000)
				.build();
			ImageCache.getInstance(this).initConfig(config).show(file, iv_hello);

	private void setImageCacheDir() {
		String imageCacheDir = Environment.getExternalStorageDirectory() + "/picasso_image";
		tv_hello.setText(imageCacheDir);
		Picasso picasso = new Picasso.Builder(this).downloader(
				new OkHttpDownloader(new File(imageCacheDir))).build();
		Picasso.setSingletonInstance(picasso);
	}

//简单加载
Picasso.with(this).load(url).into(iv_hello);
//缩放加载
Picasso.with(this).load(url).resize(512, 384).centerCrop().into(iv_hello);
//占位加载
Picasso.with(this).load(url).placeholder(R.drawable.bliss).error(R.drawable.error).into(iv_hello);

        File imageCacheDir = new File(Environment.getExternalStorageDirectory() + "/universal_image");
        ImageLoaderConfiguration config = new ImageLoaderConfiguration  
			    .Builder(this)
			    .threadPoolSize(3) //线程池内加载的数量  
			    .threadPriority(Thread.NORM_PRIORITY - 2) //设置当前线程的优先级
			    .denyCacheImageMultipleSizesInMemory() //拒绝缓存同一图片的多个尺寸版本
//			    .taskExecutor(new Executor() {
//					@Override
//					public void execute(Runnable command) {
//					}
//			    })  //设置图片加载的任务，如无必要不必重写
//			    .taskExecutorForCachedImages(new Executor() {
//					@Override
//					public void execute(Runnable command) {
//					}
//			    })  //设置已缓存的图片的加载任务，如无必要不必重写
			    .tasksProcessingOrder(QueueProcessingType.FIFO) //队列的排队算法，默认FIFO。FIFO表示先进先出，LIFO表示后进先出
			    .memoryCache(new UsingFreqLimitedMemoryCache(2 * 1024 * 1024)) //你可以通过自己的内存缓存实现  
			    .memoryCacheSize(2 * 1024 * 1024) //使用的内存大小
			    .memoryCacheSizePercentage(13) //使用的内存百分比
			    .memoryCacheExtraOptions(480, 800) //设置内存中图片的长宽 
			    .diskCache(new UnlimitedDiskCache(imageCacheDir)) //自定义磁盘的路径
			    .diskCacheSize(50 * 1024 * 1024) //使用的磁盘大小
			    .diskCacheFileCount(100) //磁盘的文件数量上限
			    .diskCacheFileNameGenerator(new Md5FileNameGenerator())//设置磁盘文件名的命名模式，默认哈希。HashCodeFileNameGenerator表示采用哈希算法，Md5FileNameGenerator表示采用MD5算法
			    .diskCacheExtraOptions(480, 800, new BitmapProcessor() {
					@Override
					public Bitmap process(Bitmap bitmap) {
						ByteArrayOutputStream baos = new ByteArrayOutputStream();
						bitmap.compress(Bitmap.CompressFormat.JPEG, 80, baos);
						ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
						return BitmapFactory.decodeStream(bais, null, null);
					}} ) //设置磁盘中图片的长宽，需自定义压缩倍率
			    .defaultDisplayImageOptions(DisplayImageOptions.createSimple()) //显示图片的选项，默认createSimple
			    .imageDownloader(new BaseImageDownloader(this, 5 * 1000, 30 * 1000)) //下载图片的超时设置，默认连接超时5秒，读取超时20秒。第二个参数表示连接超时，第三个参数表示读取超时
			    .imageDecoder(new BaseImageDecoder(false)) //对图片解码，如需缩放或旋转可在此处理
			    .writeDebugLogs() //打印调试日志。上线时需要去掉该方法
			    .build(); //开始构建配置

		DisplayImageOptions options = new DisplayImageOptions.Builder()
			.cacheInMemory(true) //设置是否在内存中缓存，默认为false
			.cacheOnDisk(true) //设置是否在磁盘中缓存，默认为false
			.resetViewBeforeLoading(false) //设置是否在加载前重置视图，默认为false
			.displayer(new FadeInBitmapDisplayer(3000))  //设置淡入淡出的时间间隔
			.imageScaleType(ImageScaleType.EXACTLY)  //设置缩放类型
			.bitmapConfig(Bitmap.Config.ARGB_8888) //设置图像的色彩模式
			.showImageOnLoading(R.drawable.bliss) //设置图片在下载期间显示的图片
			.showImageForEmptyUri(R.drawable.error)//设置图片Uri为空或是错误的时候显示的图片  
			.showImageOnFail(R.drawable.error)  //设置图片加载/解码过程中错误时候显示的图片
			.build(); //开始构建配置

String contentUrl = "content://media/external/audio/albumart/13";

String assetsUrl = Scheme.ASSETS.wrap("image.png");  

String drawableUrl = Scheme.DRAWABLE.wrap(""+R.drawable.image);

			//简单加载
			ImageLoaderConfiguration config = new ImageLoaderConfiguration.Builder(this).build();
			mLoader.init(config);
			DisplayImageOptions options = new DisplayImageOptions.Builder()
				.displayer(new FadeInBitmapDisplayer(3000))  //设置淡入淡出的时间间隔
				.build();
			mLoader.displayImage(url, iv_hello, options);
			//带监听器的加载
			ImageLoaderConfiguration config = new ImageLoaderConfiguration.Builder(this).build();
			mLoader.init(config);
			ImageSize size = new ImageSize(512, 384);
			mLoader.loadImage(url, size, new SimpleImageLoadingListener(){
				@Override
				public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage) {
					super.onLoadingComplete(imageUri, view, loadedImage);
					iv_hello.setImageBitmap(loadedImage);
				}
			});