Android开发之ImageLoader使用详解

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：

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*，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

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();
}
}
}

以上代码是小编给大家介绍的android开发之imageloader基本使用，有问题欢迎大家留言，我会及时和大家回复的，谢谢！