Android Listview异步动态加载网络图片
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
(2)定义类MapListViewCache实例化ListViewItem中的控件
(3)定义类AsyncImageLoader,开启线程下载指定图片
(4)定义类MapListImageAndTextListAdapter继承ArrayAdapter,用于创建AsyncImageLoader实例,并指定控件的内容
(5)主程序中Listview与MapListImageAndTextListAdapter的捆绑
[代码] (1)定义类MapListImageAndText管理ListViewItem中控件的内容
view sourceprint?01package com.google.zxing.client.android.AsyncLoadImage;
05public class MapListImageAndText {
06 private String imageUrl;
07 private String shopname;
08 private String activitynifo;
09 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}
[代码] (2)定义类MapListViewCache实例化ListViewItem中的控件
01package com.google.zxing.client.android.AsyncLoadImage;
02
03import com.google.zxing.client.android.R;
04
05import android.view.View;
06import android.widget.ImageView;
07import android.widget.TextView;
08
09public 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}
[代码] (3)定义类AsyncImageLoader,开启线程下载指定图片
01package com.google.zxing.client.android.AsyncLoadImage;
02
03import java.io.IOException;
04import java.io.InputStream;
05import java.lang.ref.SoftReference;
06import java.net.MalformedURLException;
07import java.net.URL;
08import java.util.HashMap;
09
10import android.graphics.drawable.Drawable;
11import android.os.Handler;
12import android.os.Message;
13
14public class AsyncImageLoader {
15
16 private HashMap> imageCache;
17
18 public AsyncImageLoader() {
19 imageCache = new HashMap>();
20 }
21
22 public Drawable loadDrawable(final String imageUrl, finalImageCallback imageCallback) {
23 if (imageCache.containsKey(imageUrl)) {
24 SoftReference 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, newSoftReference(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}
[代码] (4)定义类MapListImageAndTextListAdapter继承ArrayAdapter
01package com.google.zxing.client.android.AsyncLoadImage;
02
03import java.util.List;
04
05import com.google.zxing.client.android.R;
06
07importcom.google.zxing.client.android.AsyncLoadImage.AsyncImageLoader.ImageCallback;
08
09import android.app.Activity;
10import android.graphics.drawable.Drawable;
11import android.view.LayoutInflater;
12import android.view.View;
13import android.view.ViewGroup;
14import android.widget.ArrayAdapter;
15import android.widget.ImageView;
16import android.widget.ListView;
17import android.widget.TextView;
18
19public class MapListImageAndTextListAdapter extendsArrayAdapter {
20
21 private ListView listView;
22 private AsyncImageLoader asyncImageLoader;
23
24 public MapListImageAndTextListAdapter(Activity activity, List 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}
[代码] (5)主程序中Listview与MapListImageAndTextListAdapter的捆绑
01//tuangoupoints为对后台传回来的数据解析后得到的字符串
02String[] mtuangoupoints =tuangoupoints.split("@");
03
04List dataArray=new ArrayList();
05
06for(int i=0; i
07 String[] tonepoint=mtuangoupoints[i].split("#");
08
09 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=newMapListImageAndText(imageurl,shopname,activityinfo,address,telephone,distance);
17 dataArray.add(test);
18}
19
20MapListImageAndTextListAdapter adapter=newMapListImageAndTextListAdapter(this, dataArray, mlistView);
21mlistView.setAdapter(adapter);
