Android批量图片加载经典系列——Volley框架实现多格局的新闻列表

//创建RequestQueue，可发送异步请求RequestQueue  mRequestQueue=Volley.newRequestQueue(this);//StringRequest request=new StringRequest(…);//创建一个客户端请求mRequestQueue.add(request);//将请求加到队列，将异步执行请求

//创建ImageLoader,用于将图片存入缓存和从缓存中取出图片//第一个参数为之前创建的RequestQueue对象//第二参数为图片缓存设置，详解见BitmapCache代码ImageLoader mImageLoader=new ImageLoader(mRequestQueue,new BitmapCache());//加载图片，先从内存中加载，内存没有再从网络加载//url:图片网络路径  //view 显示图片的ImageView控件，R.drawable.default未加载完成显示的缺省图片 ，R.drawable.error加载失败显示的图片        mImageLoader.get(url,ImageLoader.getImageListener(view,                R.drawable.default, R.drawable.error));    

public class BitmapCache implements ImageCache{    private LruCache<String, Bitmap> mCache;    public BitmapCache(){    // 获取到可用内存的最大值，使用内存超出这个值会引起OutOfMemory异常    // 使用最大可用内存值的1/8作为缓存的大小。    int maxsize=(int)(Runtime.getRuntime().maxMemory()/1024)/8;    mCache=new LruCache<String, Bitmap>(maxsize){    // 重写此方法来衡量每张图片的大小，默认返回图片数量            @Override            protected int sizeOf(String key, Bitmap value) {                return super.sizeOf(key, value);            }        };    }    /**     * 获取缓存中图片     */    @Override    public Bitmap getBitmap(String key) {        return mCache.get(key);    }    /**     * 存入缓存     */    @Override    public void putBitmap(String key, Bitmap bitmap) {        if(bitmap!=null)mCache.put(key, bitmap);    }}

public class SunNewsApplication extends Application {private ImageLoader mImageLoader;       private RequestQueue mRequestQueue;public void onCreate(){//创建RequestQueue，可发送异步请求mRequestQueue=Volley.newRequestQueue(this);//创建ImageLoader,用于将图片存入缓存和从缓存中取出图片mImageLoader=new ImageLoader(mRequestQueue,new BitmapCache());        }    public ImageLoader getmImageLoader() {        return mImageLoader;    }    public RequestQueue getmRequestQueue() {        return mRequestQueue;    }}

public class MoreStyleNewsListViewAdapter extends BaseAdapter {    private Activity mActivity;    private List<NewsItem> newsList;    private ImageLoader imageLoader;    public MoreStyleNewsListViewAdapter(Activity mActivity,List<NewsItem> newsList){        this.mActivity=mActivity;        this.newsList=newsList;        imageLoader=((SunNewsApplication)mActivity.getApplication()).getmImageLoader();    }    private final int TYPE_COUNT=2;    /**     * 返回数据项的显示类型数据     */    @Override    public int getItemViewType(int position) {        return newsList!=null?newsList.get(position).getStyle():-1;    }    /**     * 返回类型个数     */    @Override    public int getViewTypeCount() {        return TYPE_COUNT;    }    @Override    public int getCount() {        return newsList.size();    }    @Override    public Object getItem(int position) {        return newsList.get(position);    }    @Override    public long getItemId(int position) {        return position;    }    @Override    public View getView(int position, View convertView, ViewGroup parent) {        ViewHolder holder=null;        NewsItem item=newsList.get(position);        if(convertView==null){        holder=new ViewHolder();        //将layout.xml转换为View        switch(item.getStyle()){            case 0:            convertView=LayoutInflater.from(mActivity).inflate(R.layout.news_item1, null);                holder.ivImg1=(ImageView)convertView.findViewById(R.id.ivNewsImg);                break;            case 1:            convertView=LayoutInflater.from(mActivity).inflate(R.layout.news_item2, null);                holder.ivImg1=(ImageView)convertView.findViewById(R.id.ivImg1);                holder.ivImg2=(ImageView)convertView.findViewById(R.id.ivImg2);                holder.ivImg3=(ImageView)convertView.findViewById(R.id.ivImg3);                break;            }        holder.tvTilte=(TextView)convertView.findViewById(R.id.tvTitle);            convertView.setTag(holder);//记录个标识        }else{            holder=(ViewHolder)convertView.getTag();        }        //向ui元素绑定数据        holder.tvTilte.setText(item.getTitle());//加载图片，先从内存中加载，内存没有再从网络加载        imageLoader.get(item.getImgUrl()[0], ImageLoader.getImageListener(holder.ivImg1,                R.drawable.default_big, R.drawable.default_big));                switch(item.getStyle()){        case 1:imageLoader.get(item.getImgUrl()[1], ImageLoader.getImageListener(holder.ivImg2,                        R.drawable.default_big, R.drawable.default_big));                    imageLoader.get(item.getImgUrl()[2], ImageLoader.getImageListener(holder.ivImg3,                        R.drawable.default_big, R.drawable.default_big));                    break;        }        Log.d("jereh","getView()");        return convertView;    }    private class ViewHolder{        private TextView tvTilte;        private ImageView ivImg1;        private ImageView ivImg2;        private ImageView ivImg3;        }}

public class MainActivity extends Activity {    private RadioGroup rgChannel;    private List<NewsItem> newsList=new ArrayList<NewsItem>();    private MoreStyleNewsListViewAdapter adapter;    private ListView newsListView;    private RequestQueue queue;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_home);        queue=((SunNewsApplication)super.getApplication()).getmRequestQueue();        initView();        requestData();        }    private void initView(){        rgChannel=(RadioGroup)super.findViewById(R.id.rgChannel);        rgChannel.check(R.id.rbToday);        newsListView=(ListView)super.findViewById(R.id.lvNews);        adapter=new MoreStyleNewsListViewAdapter(this,newsList);        newsListView.setAdapter(adapter);    }        /**     * 异步请求获得网络数据     */    private void requestData(){        String url="http://192.168.0.107:8080/21-sun/NewsListServlet";        StringRequest request=new StringRequest(Method.GET,url,         new Response.Listener<String>() {            @Override            public void onResponse(String ret) {//请求成功调用并返回结果                Gson gson=new Gson();                List list=gson.fromJson(ret, new TypeToken<ArrayList<NewsItem>>(){}.getType());                newsList.addAll(list);                adapter.notifyDataSetChanged();            }        }, new Response.ErrorListener() {            @Override            public void onErrorResponse(VolleyError error) {//请求失败调用                Log.d("jereh", "网络加载失败！");            }        });        queue.add(request);//将请求加到队列，将异步执行请求    }}

public class NewsItem {private String title;//新闻标题    private int style; //0:普通 1:多图 2:        private String[] imgUrl;//新闻图片        …//省略setter/getter}

public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        response.setContentType("text/json;charset=utf-8");    List<NewsItem> newsList=new ArrayList<NewsItem>();    NewsItem item1=new NewsItem();    item1.setTitle("英达成唯一获新疆最高信用等级的养护施工企业");    item1.setStyle(0);    item1.setImgUrl( new String[]{"http://news.21-sun.com/UserFiles/x_Image/x_20150624164627_0.jpg"});    newsList.add(item1);…    NewsItem item4=new NewsItem();    item4.setTitle("德工2015路面机械质量万里行活动走进河南");    item4.setStyle(1);item4.setImgUrl(newString[]{"http://news.21-sun.com/UserFiles/x_Image/x_20150624101251_0.jpg",        "http://news.21-sun.com/UserFiles/x_Image/x_20150624080852_0.jpg",        "http://news.21-sun.com/UserFiles/x_Image/x_20150623141354_0.jpg"});    newsList.add(item4);            NewsItem item5=new NewsItem();    item5.setTitle("德州宝鼎总经理王桂清：实在女人爱学习");    item5.setStyle(0);    item5.setImgUrl(new String[]{"http://news.21-sun.com/UserFiles/x_Image/x_20150624123300_0.jpg"});    newsList.add(item5);    JSONArray jsonArr=JSONArray.fromObject(newsList);    System.out.println(jsonArr);response.getWriter().print(jsonArr.toString());    }