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：

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

(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> imageCache;
     public AsyncImageLoader() {
imageCache = new HashMap>();
     }
     public Drawable loadDrawable(final String imageUrl, final ImageCallback imageCallback) {
if (imageCache.containsKey(imageUrl)) {
  SoftReference 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));
    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 {
    private ListView listView;
    private AsyncImageLoader asyncImageLoader;
    public MapListImageAndTextListAdapter(Activity activity, List 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 dataArray=new ArrayList();
for(int i=0; i

更多关于Android相关内容感兴趣的读者可查看本站专题：《Android视图View技巧总结》、《Android编程之activity操作技巧总结》、《Android操作SQLite数据库技巧总结》、《Android操作json格式数据技巧总结》、《Android数据库操作技巧总结》、《Android文件操作技巧汇总》、《Android编程开发之SD卡操作方法汇总》、《Android开发入门与进阶教程》、《Android资源操作技巧汇总》及《Android控件用法总结》
希望本文所述对大家Android程序设计有所帮助。