Android 模拟新闻APP显示界面滑动优化实例代码

2024-02-27 00:38:03 347
内容：
1、滑动优化（滑动时不加载图片，停止才加载）
2、第一次进入时手动加载
代码如下：
1、界面布局
2、开启异步解析数据
packagecom.example.leixiansheng.news;

/**
*CreatedbyLeixianshengon2017/3/21.
*/
publicclassNewsBean{
publicStringviewUrl;
publicStringtitle;
publicStringcontent;
}
packagecom.example.leixiansheng.news;
importandroid.os.AsyncTask;
importandroid.support.v7.app.AppCompatActivity;
importandroid.os.Bundle;
importandroid.util.Log;
importandroid.widget.ListView;
importorg.json.JSONArray;
importorg.json.JSONException;
importorg.json.JSONObject;
importjava.io.BufferedReader;
importjava.io.IOException;
importjava.io.InputStream;
importjava.io.InputStreamReader;
importjava.io.UnsupportedEncodingException;
importjava.net.URL;
importjava.util.ArrayList;
importjava.util.List;
publicclassMainActivityextendsAppCompatActivity{
privateListViewlistView;
privatestaticStringURL="http://www.imooc.com/api/teacher?type=4&num=30";
@Override
protectedvoidonCreate(BundlesavedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView=(ListView)findViewById(R.id.list_view);
newNewsAsyncTask().execute(URL);
}
//*&*异步加载，处理耗时任务,UI更新
classNewsAsyncTaskextendsAsyncTask>{
@Override
protectedListdoInBackground(String...strings){
returngetJsonData(strings[0]);
}
@Override
protectedvoidonPostExecute(ListnewsBeen){
super.onPostExecute(newsBeen);
NewsAdapteradapter=newNewsAdapter(MainActivity.this,newsBeen,listView);
listView.setAdapter(adapter);
}
}
//*&*JSON解析网页获取数据
privateListgetJsonData(Stringurl){
ListnewsBeanList=newArrayList<>();
try{
StringjsonString=readSteam(newURL(url).openStream());
Log.i("DATA",jsonString);
JSONObjectjsonObject;
NewsBeannewsBean;
try{
jsonObject=newJSONObject(jsonString);
JSONArrayjsonArray=jsonObject.getJSONArray("data");
for(inti=0;i
3、自定义适配器（在此处设置滑动监听，以此来判断什么时候加载资源）
packagecom.example.leixiansheng.news;
importandroid.content.Context;
importandroid.view.LayoutInflater;
importandroid.view.View;
importandroid.view.ViewGroup;
importandroid.widget.AbsListView;
importandroid.widget.BaseAdapter;
importandroid.widget.ImageView;
importandroid.widget.ListView;
importandroid.widget.TextView;
importjava.util.List;
/**
*CreatedbyLeixianshengon2017/3/21.
*/
publicclassNewsAdapterextendsBaseAdapterimplementsAbsListView.OnScrollListener{
privateListnewsBeanList;
privateLayoutInflaterinflater;
privateImageLoaderimageLoader;//图片加载
privateintstart;//第一个元素
privateintend;//最后一个元素
privatebooleanisFirstIn;//是否第一次进入
publicstaticString[]URLS;//所有资源
publicNewsAdapter(Contextcontext,ListnewsBeanList,ListViewlistView){
this.newsBeanList=newsBeanList;
inflater=LayoutInflater.from(context);
imageLoader=newImageLoader(listView);
URLS=newString[newsBeanList.size()];
for(inti=0;i0){
imageLoader.loadImages(start,end);
isFirstIn=false;
}
}
}
packagecom.example.leixiansheng.news;
importandroid.graphics.Bitmap;
importandroid.graphics.BitmapFactory;
importandroid.os.AsyncTask;
importandroid.os.Handler;
importandroid.os.Message;
importandroid.util.LruCache;
importandroid.widget.ImageView;
importandroid.widget.ListView;
importjava.io.BufferedInputStream;
importjava.io.IOException;
importjava.io.InputStream;
importjava.net.HttpURLConnection;
importjava.net.MalformedURLException;
importjava.net.URL;
importjava.util.HashSet;
importjava.util.Set;
/**
*CreatedbyLeixianshengon2017/3/21.
*/
publicclassImageLoader{
privateImageViewmImageView;
privateStringmUrl;
//*&*创建缓存
privateLruCachelruCache;
privateListViewlistview;
privateSetmTask;
publicImageLoader(ListViewlistview){
this.listview=listview;
mTask=newHashSet<>();
//*&*获取最大内存
intmaxMemory=(int)Runtime.getRuntime().maxMemory();
//设置缓存大小
intlruCacheSize=maxMemory/4;
lruCache=newLruCache(lruCacheSize){
@Override
protectedintsizeOf(Stringkey,Bitmapvalue){
//获取每个数据大小
returnvalue.getByteCount();
}
};
}
//添加数据到缓存
publicvoidaddBitmapToLruCache(Stringurl,Bitmapbitmap){
if(getBitmapFromLruCache(url)==null){
lruCache.put(url,bitmap);
}
}
//从缓存中获取数据
publicBitmapgetBitmapFromLruCache(Stringurl){
returnlruCache.get(url);
}
privateHandlerhandler=newHandler(){
@Override
publicvoidhandleMessage(Messagemsg){
super.handleMessage(msg);
if(mImageView.getTag().equals(mUrl)){
mImageView.setImageBitmap((Bitmap)msg.obj);
}
}
};
publicvoidshowImageByThread(ImageViewimageView,finalStringurl){
mImageView=imageView;
mUrl=url;
newThread(){
@Override
publicvoidrun(){
super.run();
Bitmapbitmap=getBitmapFromURL(url);
Messagemessage=Message.obtain();
message.obj=bitmap;
handler.sendMessage(message);
}
}.start();
}
publicBitmapgetBitmapFromURL(StringurlString){
Bitmapbitmap;
InputStreamis=null;
try{
URLurl=newURL(urlString);
HttpURLConnectionconnection=(HttpURLConnection)url.openConnection();
is=newBufferedInputStream(connection.getInputStream());
bitmap=BitmapFactory.decodeStream(is);
connection.disconnect();
//模拟网速卡顿时
//try{
//Thread.sleep(1000);
//}catch(InterruptedExceptione){
//e.printStackTrace();
//}
returnbitmap;
}catch(MalformedURLExceptione){
e.printStackTrace();
}catch(IOExceptione){
e.printStackTrace();
}finally{
try{
is.close();
}catch(IOExceptione){
e.printStackTrace();
}
}
returnnull;
}
publicvoidshowImageViewByAsyncTask(ImageViewimageView,Stringurl){
//判断是否已经缓存
Bitmapbitmap=getBitmapFromLruCache(url);
//没有缓存则从新下载
if(bitmap==null){
imageView.setImageResource(R.mipmap.ic_launcher);
}else{
imageView.setImageBitmap(bitmap);
}
}
//加载从start到end的所有图片
publicvoidloadImages(intstart,intend){
for(inti=start;i{
//privateImageViewimageView;
privateStringurl;
publicNewsAsyncTask(Stringurl){
//this.imageView=imageView;
this.url=url;
}
@Override
protectedBitmapdoInBackground(String...strings){
Stringurl=strings[0];
//从网络获取图片
Bitmapbitmap=getBitmapFromURL(url);
if(bitmap!=null){
//将不在缓存中的图片加入到缓存
addBitmapToLruCache(url,bitmap);
}
returnbitmap;
}
@Override
protectedvoidonPostExecute(Bitmapbitmap){
super.onPostExecute(bitmap);
ImageViewimageView=(ImageView)listview.findViewWithTag(url);
if(imageView!=null&&bitmap!=null){
imageView.setImageBitmap(bitmap);
}
mTask.remove(this);
}
}
}
4、注册声明权限












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Android 模拟新闻APP显示界面滑动优化实例代码

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