Android开发之ImageLoader使用详解_Android

先给大家展示效果图，看看是大家想要的效果吗，如果还满意，请参考以下代码：

Android开发之ImageLoader使用详解

前言

universalimageloader是用于加载图片的一个开源项目，在其项目介绍中是这么写的，

•支持多线程图片加载
•提供丰富的细节配置，比如线程池大小，htpp请求项，内存和磁盘缓存，图片显示时的参数配置等等；
•提供双缓存
•支持加载过程的监听；
•提供图片的个性化显示配置接口；
•widget支持(这个，个人觉得没必要写进来，不过尊重原文)

其他类似的项目也有很多，但这个作为github上著名的开源项目被广泛使用。第三方的包虽然好用省力，可以有效避免重复造轮子，但是却隐藏了一些开发上的细节，如果不关注其内部实现，那么将不利于开发人员掌握核心技术，当然也谈不上更好的使用它，计划分析项目的集成使用和低层实现。

我从接口拉出来的数据然后将它们展示在界面上

1 先定义布局我定义了mygridview来展示商品

2 导入jar包universal-image-loader-1.8.6-with-sources 用来展示商品使用在使用 imageloader应加入

imageloader.getinstance().init(imageloaderconfiguration.createdefault(this));不然会报
java.lang.illegalstateexception: imageloader must be init with configuration before using字面意思是在使用前要初始化

3 定义适配器在getview中展示产品，不过我在展示的时候发现第一条数据总是在请求数据如下图，重复网址加载太慢也消耗服务器（也不知道是我哪里写错了第0条在重复请求在网上我也没找到方法）

所以我定义了一个 view arrview[]有数据的时候就不许再请求了

Android开发之ImageLoader使用详解

4 开启子线程在子线程中加载数据，在handler中解析数据并将其展示在界面上

主要的代码如下

布局代码

				?

									package com.demo.content;

									import android.content.context;

									import android.util.attributeset;

									import android.widget.gridview;

									public class mygridview extends gridview {

									public mygridview(context context, attributeset attrs) {

									super(context, attrs);

									}

									public mygridview(context context) {

									super(context);

									}

									public mygridview(context context, attributeset attrs, int defstyle) {

									super(context, attrs, defstyle);

									}

									@override

									public void onmeasure(int widthmeasurespec, int heightmeasurespec) {

									int expandspec = measurespec.makemeasurespec(integer.max_value >> 2,

									measurespec.at_most);

									super.onmeasure(widthmeasurespec, expandspec);

									}

									} 

									<?xml version="1.0" encoding="utf-8"?>

									<linearlayout xmlns:android="http://schemas.android.com/apk/res/android"

									android:layout_width="match_parent"

									android:layout_height="match_parent"

									android:orientation="vertical" >

									<scrollview

									android:layout_width="match_parent"

									android:layout_height="match_parent" >

									<linearlayout

									android:layout_width="match_parent"

									android:layout_height="wrap_content"

									android:background="#eee"

									android:orientation="vertical" >

									<button

									android:layout_width="match_parent"

									android:layout_height="wrap_content"

									android:text="@string/app_name"

									android:textcolor="#000" />

									<view

									android:layout_width="match_parent"

									android:layout_height="5dp"

									android:background="@drawable/btn_normal" />

									<com.demo.content.mygridview

									android:id="@+id/gg_mygridview"

									android:layout_width="match_parent"

									android:layout_height="match_parent"

									android:horizontalspacing="7dp"

									android:numcolumns="2"

									android:verticalspacing="7dp" />

									</linearlayout>

									</scrollview>

									</linearlayout> 

									package com.demo.activity;

									import java.util.arraylist;

									import java.util.list;

									import org.json.jsonarray;

									import org.json.jsonobject;

									import com.demo.content.mygridview;

									import com.demo.entity.product;

									import com.demo.pullrefresh.r;

									import com.demo.util.getthread;

									import com.nostra.universalimageloader.core.displayimageoptions;

									import com.nostra.universalimageloader.core.imageloader;

									import com.nostra.universalimageloader.core.imageloaderconfiguration;

									import com.nostra.universalimageloader.core.assist.imagescaletype;

									import com.nostra.universalimageloader.core.display.fadeinbitmapdisplayer;

									import android.annotation.suppresslint;

									import android.app.activity;

									import android.graphics.bitmap;

									import android.os.bundle;

									import android.os.handler;

									import android.util.log;

									import android.view.view;

									import android.view.viewgroup;

									import android.widget.baseadapter;

									import android.widget.imageview;

									import android.widget.textview;

									public class mymainactivity extends activity {

									// 定义的布局

									private mygridview mygridview;

									private displayimageoptions options;

									// 产品

									private list<product> products;

									// 地址

									private string url = ""

									+ "product/getproductsbyprotype//";

									@override

									protected void oncreate(bundle arg) {

									// todo auto-generated method stub

									super.oncreate(arg);

									setcontentview(r.layout.mymainactivity);

									options = new displayimageoptions.builder()

									.showimageforemptyuri(r.drawable.ic_empty)

									// image连接地址为空时

									.showimageonfail(r.drawable.ic_error)

									// image加载失败

									.resetviewbeforeloading(true).cacheondisc(true)

									.imagescaletype(imagescaletype.exactly)

									.bitmapconfig(bitmap.config.rgb_)

									.displayer(new fadeinbitmapdisplayer())// 设置用户加载图片task（这里是渐现图片显示）

									.build();

									// 创建默认的imageloader的参数 不加回报java.lang.illegalstateexception

									// 但不是每次用到imageloader都要加

									imageloader.getinstance().init(

									imageloaderconfiguration.createdefault(this));

									mygridview = (mygridview) findviewbyid(r.id.gg_mygridview);

									// 开启线程

									new getthread(url, handler).start();

									}

									@suppresslint("handlerleak")

									private handler handler = new handler() {

									public void handlemessage(android.os.message msg) {

									switch (msg.what) {

									case getthread.success:

									string jsonstring = (string) msg.obj;

									// 用json来解析数据

									products = getjsonproducts(jsonstring);

									log.d("jiejie", "ddddddd" + products);

									// 创建个适配器

									adapter adapter = new adapter();

									mygridview.setadapter(adapter);

									break;

									default:

									break;

									}

									};

									};

									protected list<product> getjsonproducts(string jsonstring) {

									list<product> resulttemplist = new arraylist<product>();

									try {

									jsonarray array = new jsonarray(jsonstring);

									for (int i = ; i < array.length(); i++) {

									product temproductsimple = new product();

									jsonobject object = array.getjsonobject(i);

									temproductsimple.setid(object.getint("id"));

									temproductsimple.setprotype(object.getint("protype"));

									temproductsimple.setproorder(object.getint("proorder"));

									temproductsimple.setaddtime(object.getstring("addtime"));

									temproductsimple.settitle(object.getstring("title"));

									temproductsimple.setsmallpic(object.getstring("smallpic"));

									temproductsimple.setprice(object.getdouble("price"));

									temproductsimple.setsaleprice(object.getdouble("saleprice"));

									temproductsimple.setzhishubi(object.getstring("zhishubi"));

									temproductsimple.setprono(object.getstring("prono"));

									temproductsimple.setcontens(object.getstring("contens"));

									temproductsimple.setbuycount(object.getint("buycount"));

									temproductsimple.setreadcount(object.getint("readcount"));

									temproductsimple.setproimg(object.getstring("proimg"));

									temproductsimple.setshopflag(object.getstring("shopflag"));

									temproductsimple.setbrandid(object.getint("brandid"));

									temproductsimple.setstarttime(object.getstring("starttime"));

									if (object.get("score") == null

									|| object.get("score").tostring() == "null") {

									temproductsimple.setscore();

									} else {

									temproductsimple.setscore(object.getint("score"));

									}

									temproductsimple.setproductorigin(object

									.getstring("productorigin"));

									if (object.get("kucun").tostring() == "null") {

									temproductsimple.setkucun();

									} else {

									temproductsimple.setkucun(object.getint("kucun"));

									}

									resulttemplist.add(temproductsimple);

									}

									} catch (exception e) {

									// todo: handle exception

									e.printstacktrace();

									system.out.println(e.tostring());

									}

									return resulttemplist;

									}

									private view arrview[];

									private class adapter extends baseadapter {

									@override

									public int getcount() {

									// todo auto-generated method stub

									// return products.size();

									if (arrview == null) {

									arrview = new view[products.size()];

									}

									return products.size();

									}

									@override

									public object getitem(int arg) {

									// todo auto-generated method stub

									return products.get(arg);

									}

									@override

									public long getitemid(int arg) {

									// todo auto-generated method stub

									return arg;

									}

									@override

									public view getview(int arg, view arg, viewgroup arg) {

									if (arrview[arg] == null) {

									product info = products.get(arg);

									holder holder = null;

									if (null == arg) {

									holder = new holder();

									arg = view.inflate(mymainactivity.this,

									r.layout.product_item, null);

									holder.product_cost = (textview) arg

									.findviewbyid(r.id.product_cost);

									holder.product_title = (textview) arg

									.findviewbyid(r.id.product_title);

									holder.product_img = (imageview) arg

									.findviewbyid(r.id.product_img);

									holder.buy_count = (textview) arg

									.findviewbyid(r.id.buy_count);

									arg.settag(holder);

									} else {

									holder = (holder) arg.gettag();

									}

									holder.product_cost.settext(products.get(arg).getsaleprice()

									+ "");

									holder.product_title.settext(products.get(arg).gettitle());

									holder.buy_count.settext(products.get(arg).getbuycount() + "");

									string urlstring = "http://**/uploadimages/productimages/"

									+ products.get(arg).getsmallpic();

									log.d("jiejie", "dddddd___ " + arg);

									log.d("jiejie", "_________" + info.gettitle());

									log.d("jiejie", "productegridadapter--" + urlstring);

									imageloader.getinstance().displayimage(urlstring,

									holder.product_img, options);

									arrview[arg] = arg;

									}

									return arrview[arg];

									// return arg;

									}

									}

									static class holder {

									imageview product_img;

									textview product_title;

									textview product_cost;

									textview buy_count;

									}

									}

									package com.demo.util;

									import java.io.ioexception;

									import org.apache.http.httpresponse;

									import org.apache.http.httpstatus;

									import org.apache.http.client.clientprotocolexception;

									import org.apache.http.client.httpclient;

									import org.apache.http.client.methods.httpget;

									import org.apache.http.impl.client.defaulthttpclient;

									import org.apache.http.util.entityutils;

									import android.os.handler;

									import android.os.message;

									import android.util.log;

									public class getthread extends thread {

									public static final int success = 10, fail = -11;

									private string url;

									private handler handler;

									public getthread(string url, handler handler) {

									this.url = url;

									this.handler = handler;

									}

									@override

									public void run() {

									// todo auto-generated method stub

									super.run();

									httpclient httpclient = new defaulthttpclient();

									httpget httpget = new httpget(url);

									try {

									httpresponse httpresponse = httpclient.execute(httpget);

									message msg = message.obtain();

									log.v("asdf", httpresponse.getstatusline().getstatuscode()

									+ "返回码 " + url);

									if (httpresponse.getstatusline().getstatuscode() == httpstatus.sc_ok) {

									string jsonstring = entityutils.tostring(httpresponse

									.getentity());

									msg.what = success;

									msg.obj = jsonstring;

									handler.sendmessage(msg);

									} else {

									msg.what = fail;

									handler.sendmessage(msg);

									}

									} catch (clientprotocolexception e) {

									e.printstacktrace();

									} catch (ioexception e) {

									e.printstacktrace();

									}

									}

									}