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：
<ListViewandroid: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"?><RelativeLayoutandroid: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"><ImageViewandroid:paddingTop="2dip" android:layout_alignParentLeft="true" android:layout_width="80px" android:layout_height="80px" android:id="@+id/maplistviewitemImage"/><TextViewandroid:layout_height="wrap_content" android:textSize="17dip" android:layout_width="fill_parent" android:id="@+id/maplistviewitemshopname"android:layout_toRightOf="@id/maplistviewitemImage"android:textColor="#000000"/><TextViewandroid: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"/><TextViewandroid: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"/><TextViewandroid: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。
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