Android实现Listview异步加载网络图片并动态更新的方法

本文实例讲述了android实现listview异步加载网络图片并动态更新的方法。分享给大家供大家参考，具体如下：

应用实例：解析后台返回的数据，把每条都显示在listview中，包括活动图片、店名、活动详情、地址、电话和距离等。

在布局文件中listview的定义：

<listview
android:id="@id/maplistview" 
android:background="@drawable/bg" 
android:layout_width="fill_parent" 
android:layout_height="fill_parent" 
android:cachecolorhint="#00000000" 
android:divider="@drawable/separator" 
android:dividerheight="2.0px" 
android:layout_below="@id/mapseparator"
/>

在布局文件listviewitem,中定义活动图片、店名、活动详情、地址、电话和距离的布局

<?xml version="1.0" encoding="utf-8"?>
<relativelayout
android:id="@+id/relativelayout01" 
android:layout_width="fill_parent" 
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_height="wrap_content" 
android:paddingbottom="2dip" 
android:paddingleft="2dip" 
android:paddingright="2dip">
<imageview
android:paddingtop="2dip" 
android:layout_alignparentleft="true" 
android:layout_width="80px" 
android:layout_height="80px" 
android:id="@+id/maplistviewitemimage"/>
<textview
android:layout_height="wrap_content" 
android:textsize="17dip" 
android:layout_width="fill_parent" 
android:id="@+id/maplistviewitemshopname"
android:layout_torightof="@id/maplistviewitemimage"
android:textcolor="#000000"/>
<textview
android:layout_height="wrap_content" 
android:layout_width="fill_parent" 
android:layout_alignparentleft="true" 
android:layout_below="@+id/maplistviewitemimage" 
android:id="@+id/maplistviewitemacti" 
android:textcolor="#6c6c6c"/>
<textview
android:layout_height="wrap_content" 
android:layout_width="fill_parent" 
android:layout_alignparentleft="true" 
android:layout_below="@+id/maplistviewitemacti" 
android:id="@+id/maplistviewitemaddr" 
android:textcolor="#6c6c6c" 
android:singleline="true"/>
<textview
android:layout_height="wrap_content" 
android:layout_width="fill_parent" 
android:layout_alignparentleft="true" 
android:layout_below="@+id/maplistviewitemaddr" 
android:id="@+id/maplistviewitemtelphone" 
android:textcolor="#6c6c6c" 
android:singleline="true"/>
</relativelayout>

(1)定义类maplistimageandtext管理listviewitem中控件的内容

package com.google.zxing.client.android.asyncloadimage;
public class maplistimageandtext {
    private string imageurl;
    private string shopname;
    private string activitynifo;
    private string address;
    private string telephone;
    private string distance;
    public maplistimageandtext(string imageurl, string shopname, string activitynifo, string address, string telephone,string distance) {
      this.imageurl = imageurl;
      this.shopname = shopname;
      this.activitynifo = activitynifo;
      this.address = address;
      this.telephone = telephone;
      this.distance=distance;
    }
    public string getimageurl() {
      return imageurl;
    }
    public string getshopname() {
      return shopname;
    }
    public string getactivitynifo() {
      return activitynifo;
    }
    public string getaddress() {
      return address;
    }
    public string gettelephone() {
      return telephone;
    }
    public string getdistance() {
      return distance;
    }
}

(2)定义类maplistviewcache实例化listviewitem中的控件

package com.google.zxing.client.android.asyncloadimage;
import com.google.zxing.client.android.r;
import android.view.view;
import android.widget.imageview;
import android.widget.textview;
public class maplistviewcache {
    private view baseview;
    private textview shopname;
    private textview activitynifo;
    private textview address;
    private textview telephone;
    private textview distance;
    private imageview imageview;
    public maplistviewcache(view baseview) {
      this.baseview = baseview;
    }
    public textview getshopname() {
      if (shopname == null) {
        shopname = (textview) baseview.findviewbyid(r.id.maplistviewitemshopname);
      }
      return shopname;
    }
    public textview getactivitynifo() {
      if (activitynifo == null) {
        activitynifo = (textview) baseview.findviewbyid(r.id.maplistviewitemacti);
      }
      return activitynifo;
    }
    public textview getaddress() {
      if (address == null) {
        address = (textview) baseview.findviewbyid(r.id.maplistviewitemaddr);
      }
      return address;
    }
    public textview gettelephone() {
      if (telephone == null) {
        telephone = (textview) baseview.findviewbyid(r.id.maplistviewitemtelphone);
      }
      return telephone;
    }
    public imageview getimageview() {
      if (imageview == null) {
        imageview = (imageview) baseview.findviewbyid(r.id.maplistviewitemimage);
      }
      return imageview;
    }
    public textview getdistance() {
      if (distance == null) {
        distance = (textview) baseview.findviewbyid(r.id.maplistviewitemdistance);
      }
      return distance;
    }
}

(3)定义类asyncimageloader,开启线程下载指定图片

package com.google.zxing.client.android.asyncloadimage;
import java.io.ioexception;
import java.io.inputstream;
import java.lang.ref.softreference;
import java.net.malformedurlexception;
import java.net.url;
import java.util.hashmap;
import android.graphics.drawable.drawable;
import android.os.handler;
import android.os.message;
public class asyncimageloader {
   private hashmap<string, softreference<drawable>> imagecache;
     public asyncimageloader() {
       imagecache = new hashmap<string, softreference<drawable>>();
     }
     public drawable loaddrawable(final string imageurl, final imagecallback imagecallback) {
       if (imagecache.containskey(imageurl)) {
         softreference<drawable> softreference = imagecache.get(imageurl);
         drawable drawable = softreference.get();
         if (drawable != null) {
           return drawable;
         }
       }
       final handler handler = new handler() {
         public void handlemessage(message message) {
           imagecallback.imageloaded((drawable) message.obj, imageurl);
         }
       };
       new thread() {
         @override
         public void run() {
           drawable drawable = loadimagefromurl(imageurl);
           imagecache.put(imageurl, new softreference<drawable>(drawable));
           message message = handler.obtainmessage(0, drawable);
           handler.sendmessage(message);
         }
       }.start();
       return null;
     }
    public static drawable loadimagefromurl(string url) {
      url m;
      inputstream i = null;
      try {
        m = new url(url);
        i = (inputstream) m.getcontent();
      } catch (malformedurlexception e1) {
        e1.printstacktrace();
      } catch (ioexception e) {
        e.printstacktrace();
      }
      drawable d = drawable.createfromstream(i, "src");
      return d;
    }
     public interface imagecallback {
       public void imageloaded(drawable imagedrawable, string imageurl);
     }
}

(4)定义类maplistimageandtextlistadapter继承arrayadapter,用于创建asyncimageloader实例,并指定控件的内容

package com.google.zxing.client.android.asyncloadimage;
import java.util.list;
import com.google.zxing.client.android.r;
import com.google.zxing.client.android.asyncloadimage.asyncimageloader.imagecallback;
import android.app.activity;
import android.graphics.drawable.drawable;
import android.view.layoutinflater;
import android.view.view;
import android.view.viewgroup;
import android.widget.arrayadapter;
import android.widget.imageview;
import android.widget.listview;
import android.widget.textview;
public class maplistimageandtextlistadapter extends arrayadapter<maplistimageandtext> {
    private listview listview;
    private asyncimageloader asyncimageloader;
    public maplistimageandtextlistadapter(activity activity, list<maplistimageandtext> imageandtexts, listview listview) {
      super(activity, 0, imageandtexts);
      this.listview = listview;
      asyncimageloader = new asyncimageloader();
    }
    public view getview(int position, view convertview, viewgroup parent) {
      activity activity = (activity) getcontext();
      // inflate the views from xml
      view rowview = convertview;
      maplistviewcache viewcache;
      if (rowview == null) {
        layoutinflater inflater = activity.getlayoutinflater();
        rowview = inflater.inflate(r.layout.maplistviewitem, null);
        viewcache = new maplistviewcache(rowview);
        rowview.settag(viewcache);
      } else {
        viewcache = (maplistviewcache) rowview.gettag();
      }
      maplistimageandtext imageandtext = getitem(position);
      // load the image and set it on the imageview
      string imageurl = imageandtext.getimageurl();
      imageview imageview = viewcache.getimageview();
      imageview.settag(imageurl);
      drawable cachedimage = asyncimageloader.loaddrawable(imageurl, new imagecallback() {
        public void imageloaded(drawable imagedrawable, string imageurl) {
          imageview imageviewbytag = (imageview) listview.findviewwithtag(imageurl);
          if (imageviewbytag != null) {
            imageviewbytag.setimagedrawable(imagedrawable);
          }
        }
      });
      if (cachedimage == null) {
        imageview.setimageresource(r.drawable.refresh);
      }else{
        imageview.setimagedrawable(cachedimage);
      }
      // set the text on the textview
      textview shopname = viewcache.getshopname();
      shopname.settext(imageandtext.getshopname());
      textview activitynifo = viewcache.getactivitynifo();
      activitynifo.settext(imageandtext.getactivitynifo());
      textview address = viewcache.getaddress();
      address.settext(imageandtext.getaddress());
      textview telephone = viewcache.gettelephone();
      telephone.settext(imageandtext.gettelephone());
      textview distance = viewcache.getdistance();
      distance.settext(imageandtext.getdistance());
      return rowview;
    }
}

(5)主程序中listview与maplistimageandtextlistadapter的捆绑

//tuangoupoints为对后台传回来的数据解析后得到的字符串
string[] mtuangoupoints =tuangoupoints.split("@");
list<maplistimageandtext> dataarray=new arraylist<maplistimageandtext>();
for(int i=0; i<mtuangoupoints.length;i++){
  string[] tonepoint=mtuangoupoints[i].split("#");
  string shopname=string.valueof(i+1)+tonepoint[2];
  string activityinfo=tonepoint[1];
  string address=tonepoint[6];
  string telephone=tonepoint[7];
  string imageurl=tonepoint[8];
  string distance=tonepoint[5];
  maplistimageandtext test=new maplistimageandtext(imageurl,shopname,activityinfo,address,telephone,distance);
  dataarray.add(test);
}
maplistimageandtextlistadapter adapter=new maplistimageandtextlistadapter(this, dataarray, mlistview);
mlistview.setadapter(adapter);

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希望本文所述对大家android程序设计有所帮助。