图片三级缓存：BitmapCacheUtils

package com.itheima62.smartbj.utils;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

import android.graphics.Bitmap;
import android.graphics.Bitmap.CompressFormat;
import android.graphics.BitmapFactory;
import android.support.v4.util.LruCache;
import android.widget.ImageView;

import com.itheima62.smartbj.activity.MainActivity;

/**
 * @author Administrator
 * @创建时间 2015-7-10 下午4:13:16
 * @描述 TODO
 * 
 *     @ svn提交者：$Author: gd $ @ 提交时间: $Date: 2015-07-10 17:11:48 +0800 (Fri, 10 Jul 2015) $ @ 当前版本: $Rev: 65 $
 */
public class BitmapCacheUtils
{

    //动态获取jvm的内存
    
    private int maxSize = (int) (Runtime.getRuntime().freeMemory() / 2);
    //图片的缓存容器
    private LruCache<String, Bitmap> memCache = new LruCache<String, Bitmap>(maxSize) {

        @Override
        protected int sizeOf(String key, Bitmap value) {
            // TODO Auto-generated method stub
            return value.getRowBytes() * value.getHeight();
        }
    
    };
    //保留最后一次访问url的信息
    private Map<ImageView,String> urlImageViewDatas = new HashMap<ImageView, String>();
    
    
    
    
    private File cacheDir ;
    private MainActivity mainActivity;
    private ExecutorService    threadPool;
    
    public BitmapCacheUtils(MainActivity mainActivity) {
        this.mainActivity = mainActivity;
        //获取当前app的cache目录
        cacheDir = mainActivity.getCacheDir();
        //线程池
        threadPool = Executors.newFixedThreadPool(6);
    }
    public void display(ImageView iv, String ivUrl) {
        // 1. 先从内存取
        
        Bitmap bitmap = memCache.get(ivUrl);
        if (bitmap != null) {
            System.out.println("从内存获取数据");
            //缓存中有图片
            iv.setImageBitmap(bitmap);
            return;
        }
        
        // 2. 再从本地文件中, app（/data/data/包名/cache）
        bitmap = getCacheFile(ivUrl);
        if (bitmap != null) {
            System.out.println("从文件获取数据");
            //本地文件中有图片
            iv.setImageBitmap(bitmap);
            return;
        }
        
        // 3. 从网络取
        urlImageViewDatas.put(iv, ivUrl);//保留最后一次访问的url
        getBitmapFromNet(iv, ivUrl);
    }
    
    private void getBitmapFromNet(ImageView iv, String ivUrl) {
        //new Thread(new DownLoadUrl(iv, ivUrl)).start();
        //线程池
        threadPool.submit(new DownLoadUrl(iv, ivUrl));
    }
    
    private class DownLoadUrl implements Runnable{
        private String ivUrl;
        private ImageView iv;
        public DownLoadUrl(ImageView iv,String ivUrl){
            this.iv = iv;
            this.ivUrl = ivUrl;
        }
        @Override
        public void run() {
            //访问网络 
            try {
                URL url = new URL(ivUrl);
                HttpURLConnection con = (HttpURLConnection) url.openConnection();
                con.setConnectTimeout(6000);//设置超时时间
                con.setRequestMethod("GET");
                int code = con.getResponseCode();
                if (code == 200) {
                    //请求成功
                    InputStream inputStream = con.getInputStream();
                    final Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
                    //1.往内存中添加
                    memCache.put(ivUrl, bitmap);
                    
                    //2.往本地文件中添加
                    saveBitmapToCacheFile(bitmap,ivUrl);
                    
                    //3.显示数据
                    mainActivity.runOnUiThread(new Runnable() {
                        
                        @Override
                        public void run() {
                            System.out.println("从网络获取数据");
                            
                            // 显示图片
                            // 判断url是不是最新的
                            //是最新的 自己的数据
                            if (ivUrl.equals(urlImageViewDatas.get(iv))) {
                                //自己的数据
                                iv.setImageBitmap(bitmap);
                            }
                        }
                    });
                    
                }
                
            } catch (MalformedURLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            
        }
        
    }
    
    /**
     * 保存bitmap到cache目录的文件中
     * @param bitmap
     * @param ivUrl
     */
    public void saveBitmapToCacheFile(Bitmap bitmap,String ivUrl) {
        File file = new File(cacheDir,Md5Utils.md5(ivUrl));
        try {
            bitmap.compress(CompressFormat.JPEG, 100, new FileOutputStream(file));
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    /**
     * @param ivUrl
     *     当做缓存图片的名字
     * @return
     */
    public Bitmap getCacheFile(String ivUrl){
        //把ivUrl转换MD5值，再把md5 做文件名
        File file = new File(cacheDir,Md5Utils.md5(ivUrl));
        if (file != null  && file.exists()) {
            //文件存在
            //把文件转换成bitmap
            Bitmap bitmap = BitmapFactory.decodeFile(file.getAbsolutePath());
            
            //再往内存写
            memCache.put(ivUrl, bitmap);
            return bitmap;
        } else {
            //不存在
            return null;
        }
        
    }

}