Android Asynchronous Load learning note four: using cache to optimize the Network load image and ListView load optimization

Last Update:2015-08-11 Source: Internet

Author: User

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If you do not do any processing, directly with the network loading pictures in the case of fast speed may not be a bad feeling, but if the use of mobile traffic or network is not good, the problem comes, or users will complain that traffic is too much, or complain that the picture loading is too slow, such as from which point of view, is not a good experience! To improve the user experience, we're going to use Caching. There are many ways to cache data in android, and there are more articles about it, such as http://blog.csdn.net/dahuaishu2010_/article/details/17093139 and http://www.jb51.net/article/38162.htm and so On. Learning today is the LRU Cache. LRU (Least recently used) The least recently used algorithm, that is, under certain conditions, the LRU cache is to remove the least recently used data, to the latest read Data. And the most frequently read, but also the most read, so, using the LRU cache, we can improve the efficiency of the application and user Experience. The Andorid itself provides the LRUCache class to implement this caching algorithm. Using the LRUCache cache in Imageloader:public class Imageloader { Private lrucache<string, bitmap> mcaches;//create LruCache Object Private ImageView mimageview; Private ListView listview; Private Set<imageasynctask> mtask; @SuppressLint ("newapi") Public Imageloader (listview Listview) { This.listview = listView; Mtask = new Hashset<imageasynctask> (); int maxmemory = (int) runtime.getruntime (). maxmemory ();//get maximum available memory int cacheSize = Maxmemory/8;//maximum amount of memory to set cache data is 1/8 mcaches = new lrucache<string, bitmap> (cacheSize) { @Override protected int sizeOf (String key, Bitmap Value) { Return Value.getbytecount ()///every time the cache is cached, the size of the bitmap is Returned. } }; } @SuppressLint ("newapi") /** * Increase cache data to determine if data exists before * @description: * @author LDM * @date 2015-8-11 7:51:04 */ public void setlrucaches (String url, Bitmap Bitmap) { If (getlrucaches (url) = = Null) {//if There is no URL corresponding to bitmap in the cache, add bitmap to Mcaches Mcaches.put (url, bitmap); } } /** * Get data from the cache * @description: * @author LDM * @date 2015-8-11 7:51:22 */ @SuppressLint ("newapi") Public Bitmap getlrucaches (String Url) { Return mcaches.get (url);//get The corresponding bitmap in the cache via a URL } /** * Get to bitmap from URL * @description: * @author LDM * @date 2015-8-11 1:55:12 */ Public Bitmap Getbitmapbyurl (String Urlstr) { Bitmap Bitmap = null; InputStream is = null; try { URL url = new URL (urlstr); HttpURLConnection con = (httpurlconnection) url.openconnection (); is = new Bufferedinputstream (con.getinputstream ()); Bitmap = Bitmapfactory.decodestream (is); Con.disconnect (); Return bitmap; } Catch (Exception E) { E.printstacktrace (); } finally { try { Is.close (); } Catch (ioexception E) { E.printstacktrace (); } } Return null; } public void Loadimgbyasynctask (ImageView img, String Url) { Mimageview = img; Remove a picture from the cache Bitmap Bitmap = getlrucaches (url); if (bitmap = = Null) {//if No picture is available in, then download from the network Mimageview.setimageresource (r.drawable.ic_launcher);//set Default Picture New Imageasynctask (url). Execute (url); } Else {//cache has a picture, it is displayed directly Mimageview.setimagebitmap (bitmap); } } Private class Imageasynctask extends asynctask<string, Void, bitmap> { Private ImageView ImageView; Private String murl; Public Imageasynctask (String Murl) { This.murl = murl; } @Override Protected Bitmap doinbackground (String ... params) { Bitmap Bitmap = getbitmapbyurl (params[0]);//get pictures If (bitmap! = Null) { Setlrucaches (params[0], bitmap); } return Getbitmapbyurl (params[0]); } @Override protected void OnPostExecute (Bitmap Result) { ImageView img = (ImageView) listview.findviewwithtag (murl); If (img! = null && result! = null) { Imageview.setimagebitmap (result); } Mtask.remove (this); } } public void Setimageview (int start, int End) { for (int i = start; i < end; i++) { String URL = dataadapter.urls[i]; Bitmap Bitmap = getlrucaches (url); if (bitmap = = Null) {//if No picture is available in, then download from the network Imageasynctask task = new Imageasynctask (url); Task.execute (url); Mtask.add (task); } Else {//cache has a picture, it is displayed directly ImageView img = (ImageView) listview.findviewwithtag (url); Img.setimagebitmap (bitmap); } } } public void Stopalltask () { If (mtask.size () >0) { For (imageasynctask Task:mtask) { Task.cancel (false); } } } } Data adapter DataAdapter that corresponds to the listview:public class DataAdapter extends Baseadapter implements Onscrolllistener { Private Context mcontext; Private List<databean> List; Private Imageloader mimageloader; private int msart; private int mEnd; public static string[] URLS; Private ListView listview; Private Boolean isfirst;//is The first time to enter Public DataAdapter (Context mcontext, list<databean> List, listview Listview) { This.listview = listView; This.mcontext = mcontext; This.list = list; Mimageloader = new Imageloader (listView); URLS = new String[list.size ()]; for (int i = 0; i < list.size (); I++) { urls[i] = List.get (i). getimgurl (); } isfirst=true; Listview.setonscrolllistener (this); } @Override public int GetCount () { TODO auto-generated Method Stub return list.size (); } @Override Public Object GetItem (int arg0) { TODO auto-generated Method Stub return List.get (arg0); } @Override Public long Getitemid (int Arg0) { TODO auto-generated Method Stub Return arg0; } @Override Public View GetView (int arg0, View view, viewgroup arg2) { Viewholder holder = null; if (view = = Null) { Holder = new Viewholder (); View = Layoutinflater.from (mcontext). Inflate (r.layout.item_layout, null); HOLDER.IV = (ImageView) View.findviewbyid (r.id.item_iv); Holder.titletv = (TextView) View.findviewbyid (r.id.item_title); Holder.contenttv = (TextView) View.findviewbyid (r.id.item_content); View.settag (holder); } else { Holder = (viewholder) View.gettag (); } Holder.titleTv.setText (list.get (arg0). getTitle ()); Holder.contentTv.setText (list.get (arg0). getcontent ()); Holder.iv.setTag (list.get (arg0). getimgurl ());//set tag for ImageView New Imageloader (). loaderimagethread (holder.iv, list.get (arg0). getimgurl ());//line loads load image Mimageloader.loadimgbyasynctask (holder.iv, list.get (arg0). getimgurl ()); Return view; } /*** * The ListView is called during the flow */ @Override public void onscroll (abslistview view, int firstvisibleitem, int visibleitemcount, int Totalitemcount) { Msart = firstvisibleitem;//visible First item MEnd = Firstvisibleitem + visibleitemcount;//the last item visible If (isfirst&&visibleitemcount>0) {//data is processed the first time it is loaded Mimageloader.setimageview (msart, mEnd); isfirst=false; } } /*** * The ListView is called when the flow state changes */ @Override public void onscrollstatechanged (abslistview view, int Scrollstate) { if (scrollstate = = Scroll_state_idle) {//flow stop, load Visible item data at this time Mimageloader.setimageview (msart, mEnd); } else {//stop Loading Data Mimageloader.stopalltask (); } } Class Viewholder { TextView titletv; TextView contenttv; ImageView iv; } } Copyright Notice: This article for Bo Master original article, without Bo Master permission not Reproduced. Android Asynchronous Load learning note four: using cache to optimize the Network load image and ListView load optimization

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Android Asynchronous Load learning note four: using cache to optimize the Network load image and ListView load optimization

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