Android Image level three cache policy

<span id="Label3"></p>1. Introduction<p><p></p></p><pre><pre><code>Android缓存原理都是一样，可以自己封装。</code></pre></pre><p><p>Level Three cache:</p></p><pre><pre><code> 1.内存缓存：缓存在内存中，基于LRU（least recently used ）算法，机器重启消失。 2.本地缓存。缓存在本地中。一般键值对形式。(url,filepath) 3.网络缓存。从网络加载资源，然后缓存在内存、本地中。</code></pre></pre><p><p>2. Implementation steps</p></p><p><p>2.1 Memory Cache:</p></p><p><p>[java] View Plain Copy<br>public class Memorycacheutils {<br>Private Lrucache<string,bitmap> mmemorycache;<br>Public Memorycacheutils () {<br>Long maxmemory = runtime.getruntime (). maxmemory ()/8;//get 1/8 of the maximum allowable memory of the phone, that is, more than the specified memory, start the Recycle<br>Need to pass in the maximum allowed memory, virtual machine default memory 16M, The real machine is not necessarily the same<br>Mmemorycache=new lrucache<string,bitmap> ((int) Maxmemory) {<br>Used to calculate the size of each entry<br>@Override<br>protected int sizeOf (String key, Bitmap Value) {<br>int byteCount = Value.getbytecount ();<br>Return byteCount;<br>}<br>};<br>}<br>/**</p></p> <ul> <ul> <li> read pictures from memory </li> <li> <p> @param url <br> <em>/<br> public Bitmap getbitmapfrommemory (String Url) {<br>//bitmap bitm AP = Mmemorycache.get (url);//1. Strong Reference Method <br>/</em> 2. Weak reference method <br> Softreference<bitmap> bitmapsoftreference = Mmemorycache.get (url); <br> If (bitmapsoftreference! = Null) {<br> Bitmap Bitmap = Bitmapsoftreference.get (); <br> Return bitmap; <br>} <br> */<br> if (url==null| | "". equals (url)) {<br> return null; <br>} <br> Bitmap Bitmap = mmemorycache.get (url); </p> <pre> <code> return bitmap; </code> </pre> <p>} <br>/** </p> </li> <li> write a picture in memory </li> <li> @param url </li> <li> @param bitmap <br> <em>/<br> public void Setbitmaptomemory (String url, Bitmap Bitmap) {<br>//mmemorycache.put (url, Bitmap),//1. Strong Reference Method <br>/</em> 2. Weak reference method <br> Mmemorycache.put (url, New Softreference<> (bitmap)); <br> */<br> mmemorycache.put (url,bitmap); <br>} <br>} <br> 2.2 Local cache </li> </ul> </ul><p><p>[java] View Plain Copy<br>public class Localcacheutils {<br>private static final String cache_path= environment.getexternalstoragedirectory (). getabsolutepath () + "/my/images";<br>/**</p></p> <ul> <li><li>Read pictures from local</li></li> <li><li><p>@param URL<br>*/<br>Public Bitmap getbitmapfromlocal (String Url) {<br>String filename = null;//the URL of the picture as the file name and MD5 encryption<br>try {<br>FileName = Md5encoder.encode (url); It doesn't matter if you add or don't encrypt<br>File File=new file (cache_path,filename);<br>Bitmap Bitmap = Bitmapfactory.decodestream (new fileinputstream (file));<br>Return bitmap;<br>} catch (Exception E) {<br>E.printstacktrace ();<br>}<br>Return null;<br>}</p><p>/**</p></li></li> <li><li>After getting pictures from the network, save to local cache</li></li> <li><li>@param URL</li></li> <li><li><p>@param bitmap<br>*/<br>public void setbitmaptolocal (String Url,bitmap Bitmap) {<br>try {</p><pre><code> String fileName = MD5Encoder.encode(url);//把图片的url当做文件名,并进行MD5加密 File file=new File(CACHE_PATH,fileName); //通过得到文件的父文件,判断父文件是否存在 File parentFile = file.getParentFile(); if (!parentFile.exists()){ parentFile.mkdirs(); } //把图片保存至本地 bitmap.compress(Bitmap.CompressFormat.JPEG,100,new FileOutputStream(file)); } catch (Exception e) { e.printStackTrace(); } </code></pre><p>}<br>}<br>2.3 Network Cache</p></li></li> </ul><p><p>[java] View Plain Copy<br>public class Netcacheutils {<br>Private Localcacheutils mlocalcacheutils;<br>Private Memorycacheutils mmemorycacheutils;</p></p><pre><code>Public netcacheutils (localcacheutils localcacheutils, memorycacheutils memorycacheutils) {mLocalCacheUtils = localCa cheutils; Mmemorycacheutils = memorycacheutils; } public netcacheutils () {}/** * Download pictures from the network * @param ivpic Show pictures of ImageView * @param url to download the Picture's network address */public void GE Tbitmapfromnet (ImageView ivpic, String url) {new bitmaptask (). execute (ivpic, url);//start asynctask} public void Getb Itmapfromnet (View ivpic, String url) {new bitmaptask_view (). execute (ivpic, url);//start asynctask} public Bitmap Getb Itmapfromnet (final String url) {//start asynctask return null; }/** * Asynctask is the encapsulation of handler and thread pool * First generic: parameter type * Second generic: update progress generics * Third generic: onpostexecute return result */class bitmaptask Exte NDS asynctask<object, Void, bitmap> {private ImageView ivpic; Private String url; /** * Background time-consuming operation, existing in Sub-thread * @param params * @return */@Override protected Bitmap doinbackground ( object[] Params) {ivpic = (ImAgeview) params[0]; url = (String) params[1]; return Downloadbitmap (url); }/** * Update progress, in the main thread * @param values */@Override protected void onprogressupdate (void[] value S) {super.onprogressupdate (values); }/** * This method is executed after the time-consuming method, in the main thread * @param result */@Override protected void OnPostExecute (Bitmap R Esult) {if (result! = Null) {ivpic.setimagebitmap (result); System.out.println ("cache Pictures from the network ..."); After obtaining the picture from the network, save to local cache mlocalcacheutils.setbitmaptolocal (url, result); Save to Memory Mmemorycacheutils.setbitmaptomemory (url, result); }}}/** * Asynctask is the encapsulation of handler and thread pool * First generic: parameter type * Second generic: update progress of generics * Third generic: onpostexecute return result */@SuppressLi NT ("newapi") class Bitmaptask_view extends asynctask<object, Void, bitmap> {private View ivpic; Private String url; /** * Background time-consuming operation, existing in child threads * @param params * @return */@Override protected Bitmap doinbackground (object[] Params) { Ivpic = (View) params[0]; url = (String) params[1]; return Downloadbitmap (url); }/** * Update progress, in the main thread * @param values */@Override protected void onprogressupdate (void[] value S) {super.onprogressupdate (values); }/** * This method is executed after the time-consuming method, in the main thread * @param result */@Override protected void OnPostExecute (Bitmap R Esult) {if (result! = Null) {//ivpic.setimagebitmap (result); If (Build.VERSION.SDK_INT >= build.version_codes. Jelly_bean) {//android system is greater than or equal to API16, use SetBackground ivpic.setbackground (new Bitmapdra Wable (result)); } else {//android system is less than API16, use SetBackground ivpic.setbackgrounddrawable (new bitmapdr Awable (result)); } System.ouT.println ("cache Pictures from the network ..."); After obtaining the picture from the network, save to local cache mlocalcacheutils.setbitmaptolocal (url, result); Save to Memory Mmemorycacheutils.setbitmaptomemory (url, result); }}}/** * Network download picture * @param URL * @return */public Bitmap downloadbitmap (String url) {httpurlconnection conn = null; Try {conn = (httpurlconnection) new URL (url). openconnection (); Conn.setconnecttimeout (5000); Conn.setreadtimeout (5000); Conn.setrequestmethod ("GET"); int responsecode = Conn.getresponsecode (); if (responsecode = = 200) {//picture compression bitmapfactory.options Options = new Bitmapfactory.options (); Options.insamplesize=2;//wide and high compression for the original options.inpreferredconfig=bitmap.config.argb_4444; Bitmap Bitmap = Bitmapfactory.decodestream (conn.getinputstream (), null,options); Bitmap Bitmap=bitmapfactory.decodestream (conn.getinpuTStream ()); Return bitmap; }} catch (ioexception e) {e.printstacktrace (); }catch (Exception E) {} finally {if (conn!=null) {conn.disconnect (); }} return null; }</code></pre><p><p>}<br>2.4 Externally write a bitmaputils to invoke Them.</p></p><p><p>[java] View Plain Copy<br>public class Mybitmaputils {<br>Private Netcacheutils mnetcacheutils;<br>Private Localcacheutils mlocalcacheutils;<br>Private Memorycacheutils mmemorycacheutils;</p></p><pre><code>Public mybitmaputils () {mmemorycacheutils=new memorycacheutils (); Mlocalcacheutils=new localcacheutils (); Mnetcacheutils=new netcacheutils (mlocalcacheutils,mmemorycacheutils); } public Bitmap Getbitmap (String Url) {Bitmap bitmap=null; Bitmap=mmemorycacheutils.getbitmapfrommemory (url); If (bitmap!=null) {return bitmap; } bitmap = Mlocalcacheutils.getbitmapfromlocal (url); If (bitmap!=null) {mmemorycacheutils.setbitmaptomemory (url,bitmap); Return bitmap; } return bitmap; } public void DisPlay (ImageView ivpic, String url) {Bitmap Bitmap; Memory Cache Bitmap=mmemorycacheutils.getbitmapfrommemory (url); If (bitmap!=null) {ivpic.setimagebitmap (bitmap); LOG.D ("iamgecache", "get pictures from memory ...--->" +url); Return }//local cache bitmap = mlocalcacheutils.getbitmapfromlocal (url); If (bitmap!=null) {ivpic.setimagebitmap (bitmap); LOG.D ("IAMGECACHe "," get pictures from the local .....--> "+url); After obtaining the picture from the local, save to In-memory mmemorycacheutils.setbitmaptomemory (url,bitmap); Return }//network Cache Mnetcacheutils.getbitmapfromnet (ivpic,url); LOG.D ("iamgecache", "get Pictures from the internet .....-->" +url); } @SuppressLint ("newapi") public void DisPlay (View ivpic, String url) {Bitmap Bitmap; Memory Cache Bitmap=mmemorycacheutils.getbitmapfrommemory (url); If (bitmap!=null) {//ivpic.setimagebitmap (bitmap); If (Build.VERSION.SDK_INT >= build.version_codes. Jelly_bean) {//android system is greater than or equal to API16, use SetBackground ivpic.setbackground (new bitmapdrawable (bi tmap)); } else {//android system is less than API16, use SetBackground ivpic.setbackgrounddrawable (new bitmapdrawable (b itmap)); }//ivpic.setbackground (new bitmapdrawable (bitmap)); LOG.D ("iamgecache", "get pictures from memory ...--->" +url); Return }//local Cache bitmap = MlocalcAcheutils.getbitmapfromlocal (url); If (bitmap!=null) {//ivpic.setimagebitmap (bitmap); If (Build.VERSION.SDK_INT >= build.version_codes. Jelly_bean) {//android system is greater than or equal to API16, use SetBackground ivpic.setbackground (new bitmapdrawable (bi tmap)); } else {//android system is less than API16, use SetBackground ivpic.setbackgrounddrawable (new bitmapdrawable (b itmap)); }//ivpic.setbackground (new bitmapdrawable (bitmap)); LOG.D ("iamgecache", "get Pictures from the local .....-->" +url); After obtaining the picture from the local, save to In-memory mmemorycacheutils.setbitmaptomemory (url,bitmap); Return }//network Cache Mnetcacheutils.getbitmapfromnet (ivpic,url); Ivpic.setbackground (new bitmapdrawable (bitmap)); LOG.D ("iamgecache", "get Pictures from the internet ....-->" +url); }</code></pre><p><p>}<br>The benefits of a personal encapsulated network caching framework are easy to modify and self-aware. suitable for some scenarios where the image quality is not so high and requires a cache to reduce network access.</p></p><p><p>Android Image level three cache policy</p></p></span>