Android实现Listview异步加载网络图片并动态更新的方法

2024-03-14 08:44:03 406

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

<?xmlversion="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

packagecom.google.zxing.client.android.AsyncLoadImage;
publicclassMapListImageAndText{
privateStringimageUrl;
privateStringshopname;
privateStringactivitynifo;
privateStringaddress;
privateStringtelephone;
privateStringdistance;
publicMapListImageAndText(StringimageUrl,Stringshopname,Stringactivitynifo,Stringaddress,Stringtelephone,Stringdistance){
this.imageUrl=imageUrl;
this.shopname=shopname;
this.activitynifo=activitynifo;
this.address=address;
this.telephone=telephone;
this.distance=distance;
}
publicStringgetImageUrl(){
returnimageUrl;
}
publicStringgetShopname(){
returnshopname;
}
publicStringgetActivitynifo(){
returnactivitynifo;
}
publicStringgetAddress(){
returnaddress;
}
publicStringgetTelephone(){
returntelephone;
}
publicStringgetDistance(){
returndistance;
}
}

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

packagecom.google.zxing.client.android.AsyncLoadImage;
importcom.google.zxing.client.android.R;
importandroid.view.View;
importandroid.widget.ImageView;
importandroid.widget.TextView;
publicclassMapListViewCache{
privateViewbaseView;
privateTextViewshopname;
privateTextViewactivitynifo;
privateTextViewaddress;
privateTextViewtelephone;
privateTextViewdistance;
privateImageViewimageView;
publicMapListViewCache(ViewbaseView){
this.baseView=baseView;
}
publicTextViewgetShopname(){
if(shopname==null){
shopname=(TextView)baseView.findViewById(R.id.maplistviewitemshopname);
}
returnshopname;
}
publicTextViewgetActivitynifo(){
if(activitynifo==null){
activitynifo=(TextView)baseView.findViewById(R.id.maplistviewitemActi);
}
returnactivitynifo;
}
publicTextViewgetAddress(){
if(address==null){
address=(TextView)baseView.findViewById(R.id.maplistviewitemaddr);
}
returnaddress;
}
publicTextViewgetTelephone(){
if(telephone==null){
telephone=(TextView)baseView.findViewById(R.id.maplistviewitemtelphone);
}
returntelephone;
}
publicImageViewgetImageView(){
if(imageView==null){
imageView=(ImageView)baseView.findViewById(R.id.maplistviewitemImage);
}
returnimageView;
}
publicTextViewgetDistance(){
if(distance==null){
distance=(TextView)baseView.findViewById(R.id.maplistviewitemdistance);
}
returndistance;
}
}

(3)定义类AsyncImageLoader,开启线程下载指定图片

packagecom.google.zxing.client.android.AsyncLoadImage;
importjava.io.IOException;
importjava.io.InputStream;
importjava.lang.ref.SoftReference;
importjava.net.MalformedURLException;
importjava.net.URL;
importjava.util.HashMap;
importandroid.graphics.drawable.Drawable;
importandroid.os.Handler;
importandroid.os.Message;
publicclassAsyncImageLoader{
privateHashMap<String,SoftReference<Drawable>>imageCache;
publicAsyncImageLoader(){
imageCache=newHashMap<String,SoftReference<Drawable>>();
}
publicDrawableloadDrawable(finalStringimageUrl,finalImageCallbackimageCallback){
if(imageCache.containsKey(imageUrl)){
SoftReference<Drawable>softReference=imageCache.get(imageUrl);
Drawabledrawable=softReference.get();
if(drawable!=null){
returndrawable;
}
}
finalHandlerhandler=newHandler(){
publicvoidhandleMessage(Messagemessage){
imageCallback.imageLoaded((Drawable)message.obj,imageUrl);
}
};
newThread(){
@Override
publicvoidrun(){
Drawabledrawable=loadImageFromUrl(imageUrl);
imageCache.put(imageUrl,newSoftReference<Drawable>(drawable));
Messagemessage=handler.obtainMessage(0,drawable);
handler.sendMessage(message);
}
}.start();
returnnull;
}
publicstaticDrawableloadImageFromUrl(Stringurl){
URLm;
InputStreami=null;
try{
m=newURL(url);
i=(InputStream)m.getContent();
}catch(MalformedURLExceptione1){
e1.printStackTrace();
}catch(IOExceptione){
e.printStackTrace();
}
Drawabled=Drawable.createFromStream(i,"src");
returnd;
}
publicinterfaceImageCallback{
publicvoidimageLoaded(DrawableimageDrawable,StringimageUrl);
}
}

(4)定义类MapListImageAndTextListAdapter继承ArrayAdapter,用于创建AsyncImageLoader实例,并指定控件的内容

packagecom.google.zxing.client.android.AsyncLoadImage;
importjava.util.List;
importcom.google.zxing.client.android.R;
importcom.google.zxing.client.android.AsyncLoadImage.AsyncImageLoader.ImageCallback;
importandroid.app.Activity;
importandroid.graphics.drawable.Drawable;
importandroid.view.LayoutInflater;
importandroid.view.View;
importandroid.view.ViewGroup;
importandroid.widget.ArrayAdapter;
importandroid.widget.ImageView;
importandroid.widget.ListView;
importandroid.widget.TextView;
publicclassMapListImageAndTextListAdapterextendsArrayAdapter<MapListImageAndText>{
privateListViewlistView;
privateAsyncImageLoaderasyncImageLoader;
publicMapListImageAndTextListAdapter(Activityactivity,List<MapListImageAndText>imageAndTexts,ListViewlistView){
super(activity,0,imageAndTexts);
this.listView=listView;
asyncImageLoader=newAsyncImageLoader();
}
publicViewgetView(intposition,ViewconvertView,ViewGroupparent){
Activityactivity=(Activity)getContext();
//InflatetheviewsfromXML
ViewrowView=convertView;
MapListViewCacheviewCache;
if(rowView==null){
LayoutInflaterinflater=activity.getLayoutInflater();
rowView=inflater.inflate(R.layout.maplistviewitem,null);
viewCache=newMapListViewCache(rowView);
rowView.setTag(viewCache);
}else{
viewCache=(MapListViewCache)rowView.getTag();
}
MapListImageAndTextimageAndText=getItem(position);
//LoadtheimageandsetitontheImageView
StringimageUrl=imageAndText.getImageUrl();
ImageViewimageView=viewCache.getImageView();
imageView.setTag(imageUrl);
DrawablecachedImage=asyncImageLoader.loadDrawable(imageUrl,newImageCallback(){
publicvoidimageLoaded(DrawableimageDrawable,StringimageUrl){
ImageViewimageViewByTag=(ImageView)listView.findViewWithTag(imageUrl);
if(imageViewByTag!=null){
imageViewByTag.setImageDrawable(imageDrawable);
}
}
});
if(cachedImage==null){
imageView.setImageResource(R.drawable.refresh);
}else{
imageView.setImageDrawable(cachedImage);
}
//SetthetextontheTextView
TextViewshopname=viewCache.getShopname();
shopname.setText(imageAndText.getShopname());
TextViewactivitynifo=viewCache.getActivitynifo();
activitynifo.setText(imageAndText.getActivitynifo());
TextViewaddress=viewCache.getAddress();
address.setText(imageAndText.getAddress());
TextViewtelephone=viewCache.getTelephone();
telephone.setText(imageAndText.getTelephone());
TextViewdistance=viewCache.getDistance();
distance.setText(imageAndText.getDistance());
returnrowView;
}
}

(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=newArrayList<MapListImageAndText>();
for(inti=0;i<mtuangoupoints.length;i++){
String[]tonepoint=mtuangoupoints[i].split("#");
Stringshopname=String.valueOf(i+1)+tonepoint[2];
Stringactivityinfo=tonepoint[1];
Stringaddress=tonepoint[6];
Stringtelephone=tonepoint[7];
Stringimageurl=tonepoint[8];
Stringdistance=tonepoint[5];
MapListImageAndTexttest=newMapListImageAndText(imageurl,shopname,activityinfo,address,telephone,distance);
dataArray.add(test);
}
MapListImageAndTextListAdapteradapter=newMapListImageAndTextListAdapter(this,dataArray,mlistView);
mlistView.setAdapter(adapter);

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Android实现Listview异步加载网络图片并动态更新的方法

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