Android缓存的引用

packagecom.example.imagescan;importjava.util.concurrent.ExecutorService;importjava.util.concurrent.Executors;importandroid.graphics.Bitmap;importandroid.graphics.BitmapFactory;importandroid.graphics.Point;importandroid.os.Handler;importandroid.os.Message;importandroid.support.v4.util.LruCache;/***本地图片加载器,采用的是异步解析本地图片，单例模式利用getInstance()获取NativeImageLoader实例*调用loadNativeImage()方法加载本地图片，此类可作为一个加载本地图片的工具类**@bloghttp://blog.csdn.net/xiaanming**@authorxiaanming**/publicclassNativeImageLoader{privateLruCache<String,Bitmap>mMemoryCache;privatestaticNativeImageLoadermInstance=newNativeImageLoader();privateExecutorServicemImageThreadPool=Executors.newFixedThreadPool(1);privateNativeImageLoader(){//获取应用程序的最大内存finalintmaxMemory=(int)(Runtime.getRuntime().maxMemory()/1024);//用最大内存的1/4来存储图片finalintcacheSize=maxMemory/4;mMemoryCache=newLruCache<String,Bitmap>(cacheSize){//获取每张图片的大小@OverrideprotectedintsizeOf(Stringkey,Bitmapbitmap){returnbitmap.getRowBytes()*bitmap.getHeight()/1024;}};}/***通过此方法来获取NativeImageLoader的实例*@return*/publicstaticNativeImageLoadergetInstance(){returnmInstance;}/***加载本地图片，对图片不进行裁剪*@parampath*@parammCallBack*@return*/publicBitmaploadNativeImage(finalStringpath,finalNativeImageCallBackmCallBack){returnthis.loadNativeImage(path,null,mCallBack);}/***此方法来加载本地图片，这里的mPoint是用来封装ImageView的宽和高，我们会根据ImageView控件的大小来裁剪Bitmap*如果你不想裁剪图片，调用loadNativeImage(finalStringpath,finalNativeImageCallBackmCallBack)来加载*@parampath*@parammPoint*@parammCallBack*@return*/publicBitmaploadNativeImage(finalStringpath,finalPointmPoint,finalNativeImageCallBackmCallBack){//先获取内存中的BitmapBitmapbitmap=getBitmapFromMemCache(path);finalHandlermHander=newHandler(){@OverridepublicvoidhandleMessage(Messagemsg){super.handleMessage(msg);mCallBack.onImageLoader((Bitmap)msg.obj,path);}};//若该Bitmap不在内存缓存中，则启用线程去加载本地的图片，并将Bitmap加入到mMemoryCache中if(bitmap==null){mImageThreadPool.execute(newRunnable(){@Overridepublicvoidrun(){//先获取图片的缩略图BitmapmBitmap=decodeThumbBitmapForFile(path,mPoint==null?0:mPoint.x,mPoint==null?0:mPoint.y);Messagemsg=mHander.obtainMessage();msg.obj=mBitmap;mHander.sendMessage(msg);//将图片加入到内存缓存addBitmapToMemoryCache(path,mBitmap);}});}returnbitmap;}/***往内存缓存中添加Bitmap**@paramkey*@parambitmap*/privatevoidaddBitmapToMemoryCache(Stringkey,Bitmapbitmap){if(getBitmapFromMemCache(key)==null&&bitmap!=null){mMemoryCache.put(key,bitmap);}}/***根据key来获取内存中的图片*@paramkey*@return*/privateBitmapgetBitmapFromMemCache(Stringkey){returnmMemoryCache.get(key);}/***根据View(主要是ImageView)的宽和高来获取图片的缩略图*@parampath*@paramviewWidth*@paramviewHeight*@return*/privateBitmapdecodeThumbBitmapForFile(Stringpath,intviewWidth,intviewHeight){BitmapFactory.Optionsoptions=newBitmapFactory.Options();//设置为true,表示解析Bitmap对象，该对象不占内存options.inJustDecodeBounds=true;BitmapFactory.decodeFile(path,options);//设置缩放比例options.inSampleSize=computeScale(options,viewWidth,viewHeight);//设置为false,解析Bitmap对象加入到内存中options.inJustDecodeBounds=false;returnBitmapFactory.decodeFile(path,options);}/***根据View(主要是ImageView)的宽和高来计算Bitmap缩放比例。默认不缩放*@paramoptions*@paramwidth*@paramheight*/privateintcomputeScale(BitmapFactory.Optionsoptions,intviewWidth,intviewHeight){intinSampleSize=1;if(viewWidth==0||viewWidth==0){returninSampleSize;}intbitmapWidth=options.outWidth;intbitmapHeight=options.outHeight;//假如Bitmap的宽度或高度大于我们设定图片的View的宽高，则计算缩放比例if(bitmapWidth>viewWidth||bitmapHeight>viewWidth){intwidthScale=Math.round((float)bitmapWidth/(float)viewWidth);intheightScale=Math.round((float)bitmapHeight/(float)viewWidth);//为了保证图片不缩放变形，我们取宽高比例最小的那个inSampleSize=widthScale<heightScale?widthScale:heightScale;}returninSampleSize;}/***加载本地图片的回调接口**@authorxiaanming**/publicinterfaceNativeImageCallBack{/***当子线程加载完了本地的图片，将Bitmap和图片路径回调在此方法中*@parambitmap*@parampath*/publicvoidonImageLoader(Bitmapbitmap,Stringpath);}}
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