zoukankan      html  css  js  c++  java
  • 网络下载图片并显示代码片段

    一、DowdloadImage

    package org.app.netmusic.tool;
    
    import java.io.File;
    import java.io.FileInputStream;
    import java.io.FileNotFoundException;
    import java.io.FileOutputStream;
    import java.io.InputStream;
    import java.io.OutputStream;
    import java.net.HttpURLConnection;
    import java.net.URL;
    import java.util.Collections;
    import java.util.Map;
    import java.util.WeakHashMap;
    import java.util.concurrent.ExecutorService;
    import java.util.concurrent.Executors;
    
    import org.app.netmusic.tool.HttpTool.FileCache;
    import org.app.netmusic.tool.HttpTool.MemoryCache;
    import org.app.netmusic.tool.HttpTool.Utils;
    import org.app.qqmusicplayer.R;
    
    import android.app.Activity;
    import android.content.Context;
    import android.graphics.Bitmap;
    import android.graphics.BitmapFactory;
    import android.widget.ImageView;
    
    public class DowdloadImage {
           MemoryCache memoryCache=new MemoryCache();   
            FileCache fileCache;   
            private Map<ImageView, String> imageViews=Collections.synchronizedMap(new WeakHashMap<ImageView, String>());   
            ExecutorService executorService;    
            
            public DowdloadImage(Context context){   
                fileCache=new FileCache(context);   
                executorService=Executors.newFixedThreadPool(5);   
            }   
            
            final int stub_id = R.drawable.music;
            public void DisplayImage(String url, ImageView imageView)   
            {   
                imageViews.put(imageView, url);   
                Bitmap bitmap=memoryCache.get(url);   
                if(bitmap!=null)   
                    imageView.setImageBitmap(bitmap);   
                else  
                {   
                    queuePhoto(url, imageView);   
                    imageView.setImageResource(stub_id);   
                }   
            }   
            
            private void queuePhoto(String url, ImageView imageView)   
            {   
                PhotoToLoad p=new PhotoToLoad(url, imageView);   
                executorService.submit(new PhotosLoader(p));   
            }   
            
            private Bitmap getBitmap(String url)   
            {   
                File f=fileCache.getFile(url);   
            
                //从sd卡  
                Bitmap b = decodeFile(f);   
                if(b!=null)   
                    return b;   
            
                //从网络  
                try {   
                    Bitmap bitmap=null;   
                    URL imageUrl = new URL(url);   
                    HttpURLConnection conn = (HttpURLConnection)imageUrl.openConnection();   
                    conn.setConnectTimeout(30000);   
                    conn.setReadTimeout(30000);   
                    conn.setInstanceFollowRedirects(true);   
                    InputStream is=conn.getInputStream();   
                    OutputStream os = new FileOutputStream(f);   
                    Utils.CopyStream(is, os);   
                    os.close();   
                    bitmap = decodeFile(f);   
                    return bitmap;   
                } catch (Exception ex){   
                   ex.printStackTrace();   
                   return null;   
                }   
            }   
            
            //解码图像用来减少内存消耗  
            private Bitmap decodeFile(File f){   
                try {   
                    //解码图像大小  
                    BitmapFactory.Options o = new BitmapFactory.Options();   
                    o.inJustDecodeBounds = true;   
                    BitmapFactory.decodeStream(new FileInputStream(f),null,o);   
            
                    //找到正确的刻度值,它应该是2的幂。  
                    final int REQUIRED_SIZE=70;   
                    int width_tmp=o.outWidth, height_tmp=o.outHeight;   
                    int scale=1;   
                    while(true){   
                        if(width_tmp/2<REQUIRED_SIZE || height_tmp/2<REQUIRED_SIZE)   
                            break;   
                        width_tmp/=2;   
                        height_tmp/=2;   
                        scale*=2;   
                    }   
            
                    BitmapFactory.Options o2 = new BitmapFactory.Options();   
                    o2.inSampleSize=scale;   
                    return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);   
                } catch (FileNotFoundException e) {}   
                return null;   
            }   
            
            //任务队列  
            private class PhotoToLoad   
            {   
                public String url;   
                public ImageView imageView;   
                public PhotoToLoad(String u, ImageView i){   
                    url=u;   
                    imageView=i;   
                }   
            }   
            
            class PhotosLoader implements Runnable {   
                PhotoToLoad photoToLoad;   
                PhotosLoader(PhotoToLoad photoToLoad){   
                    this.photoToLoad=photoToLoad;   
                }   
            
                @Override  
                public void run() {   
                    if(imageViewReused(photoToLoad))   
                        return;   
                    Bitmap bmp=getBitmap(photoToLoad.url);   
                    memoryCache.put(photoToLoad.url, bmp);   
                    if(imageViewReused(photoToLoad))   
                        return;   
                    BitmapDisplayer bd=new BitmapDisplayer(bmp, photoToLoad);   
                    Activity a=(Activity)photoToLoad.imageView.getContext();   
                    a.runOnUiThread(bd);   
                }   
            }   
            
            boolean imageViewReused(PhotoToLoad photoToLoad){   
                String tag=imageViews.get(photoToLoad.imageView);   
                if(tag==null || !tag.equals(photoToLoad.url))   
                    return true;   
                return false;   
            }   
            
            //用于显示位图在UI线程  
            class BitmapDisplayer implements Runnable   
            {   
                Bitmap bitmap;   
                PhotoToLoad photoToLoad;   
                public BitmapDisplayer(Bitmap b, PhotoToLoad p){bitmap=b;photoToLoad=p;}   
                public void run()   
                {   
                    if(imageViewReused(photoToLoad))   
                        return;   
                    if(bitmap!=null)   
                        photoToLoad.imageView.setImageBitmap(bitmap);   
                    else  
                        photoToLoad.imageView.setImageResource(stub_id);   
                }   
            }   
            
            public void clearCache() {   
                memoryCache.clear();   
                fileCache.clear();   
            }
    }

    二、HttpTool

    package com.ct.app.netmusic;
    
    import java.io.File;
    import java.io.InputStream;
    import java.io.OutputStream;
    import java.lang.ref.SoftReference;
    import java.util.Collections;
    import java.util.HashMap;
    import java.util.Map;
    
    import android.content.Context;
    import android.graphics.Bitmap;
    
    public class HttpTool {
        public static class MemoryCache{
            private Map<String, SoftReference<Bitmap>> cache=Collections.synchronizedMap(new HashMap<String, SoftReference<Bitmap>>());//软引用  
            
            public Bitmap get(String id){  
                if(!cache.containsKey(id))  
                    return null;  
                SoftReference<Bitmap> ref=cache.get(id);  
                return ref.get();  
            }  
              
            public void put(String id, Bitmap bitmap){  
                cache.put(id, new SoftReference<Bitmap>(bitmap));  
            }  
          
            public void clear() {  
                cache.clear();  
            }  
        }
        public static class FileCache{
             private File cacheDir;  
             public FileCache(Context context){  
                    //找一个用来缓存图片的路径  
                    if (android.os.Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED))  
                        cacheDir=new File(android.os.Environment.getExternalStorageDirectory(),"musicLists");  
                    else  
                        cacheDir=context.getCacheDir();  
                    if(!cacheDir.exists())  
                        cacheDir.mkdirs();  
                }  
                  
                public File getFile(String url){  
                      
                    String filename=String.valueOf(url.hashCode());  
                    File f = new File(cacheDir, filename);  
                    return f;  
                      
                }  
                  
                public void clear(){  
                    File[] files=cacheDir.listFiles();  
                    if(files==null)  
                        return;  
                    for(File f:files)  
                        f.delete();  
                }  
              
        }
        public static class Utils{
            public static void CopyStream(InputStream is, OutputStream os)  
            {  
                final int buffer_size=1024;  
                try  
                {  
                    byte[] bytes=new byte[buffer_size];  
                    for(;;)  
                    {  
                      int count=is.read(bytes, 0, buffer_size);  
                      if(count==-1)  
                          break;  
                      os.write(bytes, 0, count);  
                     
                    }  
                    is.close();  
                    os.close();  
                }  
                catch(Exception ex){}  
            }  
        }
    }

    三、使用

    imageLoader.DisplayImage(song.get(MusicOnlineActivity.KEY_THUMB_URL), thumb_image);  

  • 相关阅读:
    IE下PNG透明图片fadeIn出现黑边的问题
    愿闻其翔记(一)
    简单的日期选择器
    HTML5 贪吃蛇
    HTML5小程序,变化的色彩
    HTML5 Canvas 基本图形画法
    帝国CMS实现一二级导航及其高亮
    php中json_decode()和json_encode()
    JavaScript重复元素处理
    JQuery在光标位置插入内容
  • 原文地址:https://www.cnblogs.com/ct732003684/p/2853017.html
Copyright © 2011-2022 走看看