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。