listview 异步加载图片

(1)定义类MapListImageAndText管理ListViewItem中控件的内容 

Java代码  

1. package com.google.zxing.client.android.AsyncLoadImage;  
2.   
3.   
4.   
5. public class MapListImageAndText {  
6.         private String imageUrl;  
7.         private String shopname;  
8.         private String activitynifo;  
9.         private String address;  
10.         private String telephone;  
11.         private String distance;  
12.           
13.         public MapListImageAndText(String imageUrl, String shopname, String activitynifo, String address, String telephone,String distance) {  
14.             this.imageUrl = imageUrl;  
15.             this.shopname = shopname;  
16.             this.activitynifo = activitynifo;  
17.             this.address = address;  
18.             this.telephone = telephone;  
19.             this.distance=distance;  
20.         }  
21.   
22.         public String getImageUrl() {  
23.             return imageUrl;  
24.         }  
25.           
26.         public String getShopname() {  
27.             return shopname;  
28.         }  
29.   
30.         public String getActivitynifo() {  
31.             return activitynifo;  
32.         }  
33.   
34.         public String getAddress() {  
35.             return address;  
36.         }  
37.   
38.         public String getTelephone() {  
39.             return telephone;  
40.         }  
41.           
42.         public String getDistance() {  
43.             return distance;  
44.         }  
45.   
46.           
47. }  

(2)定义类MapListViewCache实例化ListViewItem中的控件 

Java代码  

1. package com.google.zxing.client.android.AsyncLoadImage;  
2.   
3. import com.google.zxing.client.android.R;  
4.   
5. import android.view.View;  
6. import android.widget.ImageView;  
7. import android.widget.TextView;  
8.   
9. public class MapListViewCache {  
10.   
11.         private View baseView;  
12.         private TextView shopname;  
13.         private TextView activitynifo;  
14.         private TextView address;  
15.         private TextView telephone;  
16.         private TextView distance;  
17.   
18.         private ImageView imageView;  
19.   
20.         public MapListViewCache(View baseView) {  
21.             this.baseView = baseView;  
22.         }  
23.   
24.         public TextView getShopname() {  
25.             if (shopname == null) {  
26.                 shopname = (TextView) baseView.findViewById(R.id.maplistviewitemshopname);  
27.             }  
28.             return shopname;  
29.         }  
30.           
31.         public TextView getActivitynifo() {  
32.             if (activitynifo == null) {  
33.                 activitynifo = (TextView) baseView.findViewById(R.id.maplistviewitemActi);  
34.             }  
35.             return activitynifo;  
36.         }  
37.           
38.         public TextView getAddress() {  
39.             if (address == null) {  
40.                 address = (TextView) baseView.findViewById(R.id.maplistviewitemaddr);  
41.             }  
42.             return address;  
43.         }  
44.           
45.         public TextView getTelephone() {  
46.             if (telephone == null) {  
47.                 telephone = (TextView) baseView.findViewById(R.id.maplistviewitemtelphone);  
48.             }  
49.             return telephone;  
50.         }  
51.   
52.         public ImageView getImageView() {  
53.             if (imageView == null) {  
54.                 imageView = (ImageView) baseView.findViewById(R.id.maplistviewitemImage);  
55.             }  
56.             return imageView;  
57.         }  
58.           
59.         public TextView getDistance() {  
60.             if (distance == null) {  
61.                 distance = (TextView) baseView.findViewById(R.id.maplistviewitemdistance);  
62.             }  
63.             return distance;  
64.         }  
65.   
66. }  

(3)定义类AsyncImageLoader,开启线程下载指定图片 

Java代码  

1. package com.google.zxing.client.android.AsyncLoadImage;  
2.   
3. import java.io.IOException;  
4. import java.io.InputStream;  
5. import java.lang.ref.SoftReference;  
6. import java.net.MalformedURLException;  
7. import java.net.URL;  
8. import java.util.HashMap;  
9.   
10. import android.graphics.drawable.Drawable;  
11. import android.os.Handler;  
12. import android.os.Message;  
13.   
14. public class AsyncImageLoader {  
15.   
16.      private HashMap<String, SoftReference<Drawable>> imageCache;  
17.         
18.          public AsyncImageLoader() {  
19.              imageCache = new HashMap<String, SoftReference<Drawable>>();  
20.          }  
21.         
22.          public Drawable loadDrawable(final String imageUrl, final ImageCallback imageCallback) {  
23.              if (imageCache.containsKey(imageUrl)) {  
24.                  SoftReference<Drawable> softReference = imageCache.get(imageUrl);  
25.                  Drawable drawable = softReference.get();  
26.                  if (drawable != null) {  
27.                      return drawable;  
28.                  }  
29.              }  
30.              final Handler handler = new Handler() {  
31.                  public void handleMessage(Message message) {  
32.                      imageCallback.imageLoaded((Drawable) message.obj, imageUrl);  
33.                  }  
34.              };  
35.              new Thread() {  
36.                  @Override  
37.                  public void run() {  
38.                      Drawable drawable = loadImageFromUrl(imageUrl);  
39.                      imageCache.put(imageUrl, new SoftReference<Drawable>(drawable));  
40.                      Message message = handler.obtainMessage(0, drawable);  
41.                      handler.sendMessage(message);  
42.                  }  
43.              }.start();  
44.              return null;  
45.          }  
46.         
47.         public static Drawable loadImageFromUrl(String url) {  
48.             URL m;  
49.             InputStream i = null;  
50.             try {  
51.                 m = new URL(url);  
52.                 i = (InputStream) m.getContent();  
53.             } catch (MalformedURLException e1) {  
54.                 e1.printStackTrace();  
55.             } catch (IOException e) {  
56.                 e.printStackTrace();  
57.             }  
58.             Drawable d = Drawable.createFromStream(i, "src");  
59.             return d;  
60.         }  
61.         
62.          public interface ImageCallback {  
63.              public void imageLoaded(Drawable imageDrawable, String imageUrl);  
64.          }  
65.   
66. }  

(4)定义类MapListImageAndTextListAdapter继承ArrayAdapter 

Java代码  

1. package com.google.zxing.client.android.AsyncLoadImage;  
2.   
3. import java.util.List;  
4.   
5. import com.google.zxing.client.android.R;  
6.   
7. import com.google.zxing.client.android.AsyncLoadImage.AsyncImageLoader.ImageCallback;  
8.   
9. import android.app.Activity;  
10. import android.graphics.drawable.Drawable;  
11. import android.view.LayoutInflater;  
12. import android.view.View;  
13. import android.view.ViewGroup;  
14. import android.widget.ArrayAdapter;  
15. import android.widget.ImageView;  
16. import android.widget.ListView;  
17. import android.widget.TextView;  
18.   
19. public class MapListImageAndTextListAdapter extends ArrayAdapter<MapListImageAndText> {  
20.   
21.         private ListView listView;  
22.         private AsyncImageLoader asyncImageLoader;  
23.   
24.         public MapListImageAndTextListAdapter(Activity activity, List<MapListImageAndText> imageAndTexts, ListView listView) {  
25.             super(activity, 0, imageAndTexts);  
26.             this.listView = listView;  
27.             asyncImageLoader = new AsyncImageLoader();  
28.         }  
29.   
30.         public View getView(int position, View convertView, ViewGroup parent) {  
31.             Activity activity = (Activity) getContext();  
32.   
33.             // Inflate the views from XML  
34.             View rowView = convertView;  
35.             MapListViewCache viewCache;  
36.             if (rowView == null) {  
37.                 LayoutInflater inflater = activity.getLayoutInflater();  
38.                 rowView = inflater.inflate(R.layout.maplistviewitem, null);  
39.                 viewCache = new MapListViewCache(rowView);  
40.                 rowView.setTag(viewCache);  
41.             } else {  
42.                 viewCache = (MapListViewCache) rowView.getTag();  
43.             }  
44.             MapListImageAndText imageAndText = getItem(position);  
45.   
46.             // Load the image and set it on the ImageView  
47.             String imageUrl = imageAndText.getImageUrl();  
48.             ImageView imageView = viewCache.getImageView();  
49.             imageView.setTag(imageUrl);  
50.             Drawable cachedImage = asyncImageLoader.loadDrawable(imageUrl, new ImageCallback() {  
51.                   
52.                   
53.                 public void imageLoaded(Drawable imageDrawable, String imageUrl) {  
54.                     ImageView imageViewByTag = (ImageView) listView.findViewWithTag(imageUrl);  
55.                     if (imageViewByTag != null) {  
56.                         imageViewByTag.setImageDrawable(imageDrawable);  
57.                     }  
58.                 }  
59.             });  
60.             if (cachedImage == null) {  
61.                 imageView.setImageResource(R.drawable.refresh);  
62.             }else{  
63.                 imageView.setImageDrawable(cachedImage);  
64.             }  
65.             // Set the text on the TextView  
66.             TextView shopname = viewCache.getShopname();  
67.             shopname.setText(imageAndText.getShopname());  
68.               
69.             TextView activitynifo = viewCache.getActivitynifo();  
70.             activitynifo.setText(imageAndText.getActivitynifo());  
71.               
72.             TextView address = viewCache.getAddress();  
73.             address.setText(imageAndText.getAddress());  
74.               
75.             TextView telephone = viewCache.getTelephone();  
76.             telephone.setText(imageAndText.getTelephone());  
77.               
78.             TextView distance = viewCache.getDistance();  
79.             distance.setText(imageAndText.getDistance());  
80.               
81.             return rowView;  
82.         }  
83.   
84. }  

(5)主程序中Listview与MapListImageAndTextListAdapter的捆绑 

Java代码  

1. //tuangoupoints为对后台传回来的数据解析后得到的字符串  
2. String[] mtuangoupoints =tuangoupoints.split("@");  
3.   
4. List<MapListImageAndText> dataArray=new ArrayList<MapListImageAndText>();  
5.       
6. for(int i=0; i<mtuangoupoints.length;i++){  
7.     String[] tonepoint=mtuangoupoints[i].split("#");  
8.       
9.     String shopname=String.valueOf(i+1)+tonepoint[2];  
10.     String activityinfo=tonepoint[1];  
11.     String address=tonepoint[6];  
12.     String telephone=tonepoint[7];  
13.     String imageurl=tonepoint[8];  
14.     String distance=tonepoint[5];  
15.       
16.     MapListImageAndText test=new MapListImageAndText(imageurl,shopname,activityinfo,address,telephone,distance);  
17.     dataArray.add(test);  
18. }        
19. MapListImageAndTextListAdapter adapter=new MapListImageAndTextListAdapter(this, dataArray, mlistView);  
20. mlistView.setAdapter(adapter);  

转载： http://jykenan.iteye.com/blog/1853133