三级缓存

LocalCacheUtils

package com.itheima.zhbj52.utils.bitmap;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;

import com.itheima.zhbj52.utils.MD5Encoder;

import android.graphics.Bitmap;
import android.graphics.Bitmap.CompressFormat;
import android.graphics.BitmapFactory;
import android.os.Environment;

/**
 * 本地缓存
 * 
 * @author Kevin
 * 
 */
public class LocalCacheUtils {

    public static final String CACHE_PATH = Environment
            .getExternalStorageDirectory().getAbsolutePath() + "/zhbj_cache_52";

    /**
     * 从本地sdcard读图片
     */
    public Bitmap getBitmapFromLocal(String url) {
        try {
            String fileName = MD5Encoder.encode(url);
            File file = new File(CACHE_PATH, fileName);

            if (file.exists()) {
                Bitmap bitmap = BitmapFactory.decodeStream(new FileInputStream(
                        file));
                return bitmap;
            }

        } catch (Exception e) {
            e.printStackTrace();
        }

        return null;
    }

    /**
     * 向sdcard写图片
     * 
     * @param url
     * @param bitmap
     */
    public void setBitmapToLocal(String url, Bitmap bitmap) {
        try {
            String fileName = MD5Encoder.encode(url);

            File file = new File(CACHE_PATH, fileName);

            File parentFile = file.getParentFile();
            if (!parentFile.exists()) {// 如果文件夹不存在, 创建文件夹
                parentFile.mkdirs();
            }

            // 将图片保存在本地
            bitmap.compress(CompressFormat.JPEG, 100,
                    new FileOutputStream(file));
        } catch (Exception e) {
            e.printStackTrace();
        }

    }
}

NetCacheUtils

package com.itheima.zhbj52.utils.bitmap;

import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.widget.ImageView;

/**
 * 网络缓存
 * 
 * @author Kevin
 * 
 */
public class NetCacheUtils {

    private LocalCacheUtils mLocalCacheUtils;
    private MemoryCacheUtils mMemoryCacheUtils;

    public NetCacheUtils(LocalCacheUtils localCacheUtils,
            MemoryCacheUtils memoryCacheUtils) {
        mLocalCacheUtils = localCacheUtils;
        mMemoryCacheUtils = memoryCacheUtils;
    }

    /**
     * 从网络下载图片
     * 
     * @param ivPic
     * @param url
     */
    public void getBitmapFromNet(ImageView ivPic, String url) {
        new BitmapTask().execute(ivPic, url);// 启动AsyncTask,
                                                // 参数会在doInbackground中获取
    }

    /**
     * Handler和线程池的封装
     * 
     * 第一个泛型: 参数类型 第二个泛型: 更新进度的泛型, 第三个泛型是onPostExecute的返回结果
     * 
     * @author Kevin
     * 
     */
    class BitmapTask extends AsyncTask<Object, Void, Bitmap> {

        private ImageView ivPic;
        private String url;

        /**
         * 后台耗时方法在此执行, 子线程
         */
        @Override
        protected Bitmap doInBackground(Object... params) {
            ivPic = (ImageView) params[0];
            url = (String) params[1];

            ivPic.setTag(url);// 将url和imageview绑定

            return downloadBitmap(url);
        }

        /**
         * 更新进度, 主线程
         */
        @Override
        protected void onProgressUpdate(Void... values) {
            super.onProgressUpdate(values);
        }

        /**
         * 耗时方法结束后,执行该方法, 主线程
         */
        @Override
        protected void onPostExecute(Bitmap result) {
            if (result != null) {
                String bindUrl = (String) ivPic.getTag();

                if (url.equals(bindUrl)) {// 确保图片设定给了正确的imageview
                    ivPic.setImageBitmap(result);
                    mLocalCacheUtils.setBitmapToLocal(url, result);// 将图片保存在本地
                    mMemoryCacheUtils.setBitmapToMemory(url, result);// 将图片保存在内存
                    System.out.println("从网络缓存读取图片啦...");
                }
            }
        }
    }

    /**
     * 下载图片
     * 
     * @param url
     * @return
     */
    private Bitmap downloadBitmap(String url) {

        HttpURLConnection conn = null;
        try {
            conn = (HttpURLConnection) new URL(url).openConnection();

            conn.setConnectTimeout(5000);
            conn.setReadTimeout(5000);
            conn.setRequestMethod("GET");
            conn.connect();

            int responseCode = conn.getResponseCode();
            if (responseCode == 200) {
                InputStream inputStream = conn.getInputStream();

                //图片压缩处理
                BitmapFactory.Options option = new BitmapFactory.Options();
                option.inSampleSize = 2;//宽高都压缩为原来的二分之一, 此参数需要根据图片要展示的大小来确定
                option.inPreferredConfig = Bitmap.Config.RGB_565;//设置图片格式

                Bitmap bitmap = BitmapFactory.decodeStream(inputStream, null, option);
                return bitmap;
            }

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            conn.disconnect();
        }

        return null;
    }

}

MemoryCacheUtils

package com.itheima.zhbj52.utils.bitmap;

import android.graphics.Bitmap;
import android.support.v4.util.LruCache;

/**
 * 内存缓存
 * 
 * @author Kevin
 * 
 */
public class MemoryCacheUtils {

    // private HashMap<String, SoftReference<Bitmap>> mMemoryCache = new
    // HashMap<String, SoftReference<Bitmap>>();
    private LruCache<String, Bitmap> mMemoryCache;

    public MemoryCacheUtils() {
        long maxMemory = Runtime.getRuntime().maxMemory() / 8;// 模拟器默认是16M
        mMemoryCache = new LruCache<String, Bitmap>((int) maxMemory) {
            @Override
            protected int sizeOf(String key, Bitmap value) {
                int byteCount = value.getRowBytes() * value.getHeight();// 获取图片占用内存大小
                return byteCount;
            }
        };
    }

    /**
     * 从内存读
     * 
     * @param url
     */
    public Bitmap getBitmapFromMemory(String url) {
        // SoftReference<Bitmap> softReference = mMemoryCache.get(url);
        // if (softReference != null) {
        // Bitmap bitmap = softReference.get();
        // return bitmap;
        // }
        return mMemoryCache.get(url);
    }

    /**
     * 写内存
     * 
     * @param url
     * @param bitmap
     */
    public void setBitmapToMemory(String url, Bitmap bitmap) {
        // SoftReference<Bitmap> softReference = new
        // SoftReference<Bitmap>(bitmap);
        // mMemoryCache.put(url, softReference);
        mMemoryCache.put(url, bitmap);
    }
}