LruCache使用实例

http://geyubin.iteye.com/blog/1507567

    //需要导入外部jar文件 android-support-v4.jar  
    import android.support.v4.util.LruCache;  
    //开辟8M Strong Reference Cache
    private final int hardCachedSize = 8*1024*1024;       
    //hard cache  
    private final LruCache sHardBitmapCache = new LruCache(hardCachedSize){  
        @Override  
        public int sizeOf(String key, Bitmap value){  
            return value.getRowBytes() * value.getHeight();  
        }  
        @Override  
        protected void entryRemoved(boolean evicted, String key, Bitmap oldValue, Bitmap newValue){  
            Log.v("tag", "hard cache is full , push to soft cache");  
            // Strong Reference Cache满，将一个最不经常使用的oldvalue推入到Soft Reference Cache
            sSoftBitmapCahe.put(key, new SoftReference(oldValue));  
        }  
    }  
    //Soft Reference Cache  
    private static final int SOFT_CACHE_CAPACITY = 40;  
    private final static LinkedHashMap> sSoftBitmapCache =   
        new  LinkedHashMap>(SOFT_CACHE_CAPACITY, 0.75f, true){  
        @Override  
        public SoftReference put(String key, SoftReference value){  
            return super.put(key, value);  
        }  
        @Override  
        protected boolean removeEldestEntry(LinkedHashMap.Entry> eldest){  
            if(size() > SOFT_CACHE_CAPACITY){  
                Log.v("tag", "Soft Reference limit , purge one");  
                return true;  
            }  
            return false;  
        }  
    }  
    //缓存bitmap  
    public boolean putBitmap(String key, Bitmap bitmap){  
        if(bitmap != null){  
            synchronized(sHardBitmapCache){  
                sHardBitmapCache.put(key, bitmap);  
            }  
            return true;  
        }         
        return false;  
    }  
    //从缓存中获取bitmap  
    public Bitmap getBitmap(String key){  
        synchronized(sHardBitmapCache){  
            final Bitmap bitmap = sHardBitmapCache.get(key);  
            if(bitmap != null)  
                return bitmap;  
        }  
        //硬引用缓存区间中读取失败，从软引用缓存区间读取  
        synchronized(sSoftBitmapCache){  
            SoftReference bitmapReference = sSoftBtimapCache.get(key);  
            if(bitmapReference != null){  
                final Bitmap bitmap2 = bitmapReference.get();  
                if(bitmap2 != null)  
                    return bitmap2;  
                else{  
                    Log.v("tag", "soft reference 已经被回收");  
                    sSoftBitmapCache.remove(key);  
                }  
            }  
        }  
        return null;  
    }  

private File mCacheDir = context.getCacheDir();  
    private static final int MAX_CACHE_SIZE = 20 * 1024 * 1024; //20M  
    private final LruCache sFileCache = new LruCache(MAX_CACHE_SIZE){  
        @Override  
        public int sizeOf(String key, Long value){  
            return value.intValue();  
        }  
        @Override  
        protected void entryRemoved(boolean evicted, String key, Long oldValue, Long newValue){  
            File file = getFile(key);  
            if(file != null)  
                file.delete();  
        }  
    }  
    private File getFile(String fileName) throws FileNotFoundException {  
        File file = new File(mCacheDir, fileName);  
        if(!file.exists() || !file.isFile())  
            throw new FileNotFoundException("文件不存在或有同名文件夹");  
        return file;  
    }  
    //缓存bitmap到外部存储  
    public boolean putBitmap(String key, Bitmap bitmap){  
        File file = getFile(key);  
        if(file != null){  
            Log.v("tag", "文件已经存在");  
            return true;  
        }  
        FileOutputStream fos = getOutputStream(key);  
        boolean saved = bitmap.compress(CompressFormat.JPEG, 100, fos);  
        fos.flush();  
        fos.close();  
        if(saved){  
            synchronized(sFileCache){  
                sFileCache.put(key, getFile(key).length());  
            }  
            return true;   
        }  
        return false;  
    }  
    //根据key获取OutputStream  
    private FileOutputStream getOutputStream(String key){  
        if(mCacheDir == null)  
            return null;  
        FileOutputStream fos = new FileOutputStream(mCacheDir.getAbsolutePath() + File.separator + key);  
        return fos;  
    }  
    //获取bitmap  
    private static BitmapFactory.Options sBitmapOptions;  
    static {  
        sBitmapOptions = new BitmapFactory.Options();  
        sBitmapOptions.inPurgeable=true; //bitmap can be purged to disk  
    }  
    public Bitmap getBitmap(String key){  
        File bitmapFile = getFile(key);  
        if(bitmapFile != null){  
            Bitmap bitmap = BitmapFactory.decodeStream(new FileInputStream(bitmapFile), null, sBitmapOptions);  
            if(bitmap != null){  
                //重新将其缓存至硬引用中  
                ...  
            }  
        }  
    }  

private static String generateKey(String fileId, int width, int height) {         
        String ret = fileId + "_" + Integer.toString(width) + "x" + Integer.toString(height);  
        return ret;  
    }  
    String key = generateKey(...)即可生成唯一的key值