DiskLrucCache使用Demo(强烈推荐，非常好用)

DiskLrucCache使用的Demo，这个demo是从网络获取一张图片，保存到本地缓存中(sdcard和内存)，当下载成功后。再打开不会又一次向网络请求图片。而是世界使用本地资源。

要使用DiskLrucCache须要先下载此类.   下载地址点这里

主类：

/**
 * DiskLrucCache使用Demo
 *
 * @author pangzf
 * @date 2014年8月12日 下午2:13:26
 */
public class DemoActivity extends Activity {

    private DiskLruCache mDiskLrucache;
    private ImageView mIvShow;
    private String mBitMapUrl;
    private String mKey;
    private ProgressDialog mPd;
    private Handler mHandler = new Handler() {

        @Override
        public void dispatchMessage(Message msg) {
            super.dispatchMessage(msg);
            // 10.下载图片之后展示
            boolean isSuccess = (boolean) msg.obj;
            if (isSuccess) {
                Snapshot snapshot;
                try {
                    snapshot = mDiskLrucache.get(mKey);
                    InputStream is = snapshot.getInputStream(0);
                    mIvShow.setImageBitmap(BitmapFactory.decodeStream(is));
                } catch (IOException e) {
                    e.printStackTrace();
                }

            }
            if (mPd != null && mPd.isShowing()) {
                mPd.dismiss();
            }
        }

    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_demo);
        mIvShow = (ImageView) findViewById(R.id.iv_show);
        mPd = new ProgressDialog(DemoActivity.this);
        try {
            // 1.存放缓存的文件夹
            File directory = DiskLrucacheUtils.getDiskCache(DemoActivity.this,
                    "bitmap");
            // 2.版本
            int appVersion = DiskLrucacheUtils.getAppVersion(DemoActivity.this);
            int valueCount = 1;
            // 3.缓存的最大值，这里设置10m
            long maxSize = 10 * 1024 * 1024;
            // 4.打开disklrucache
            mDiskLrucache = DiskLruCache.open(directory, appVersion,
                    valueCount, maxSize);
            mBitMapUrl = "https://raw.githubusercontent.com/pangzaifei/LineChartView/master/LineChartView/effice_picture/a.jpg";
            if (mDiskLrucache != null) {
                // 5.假设在缓存中存在就用缓存中的bitmap，假设不存在上网上下载
                mKey = DiskLrucacheUtils.getKey(mBitMapUrl);
                Snapshot snapshot = mDiskLrucache.get(mKey);
                if (snapshot != null) {
                    InputStream is = snapshot.getInputStream(0);
                    Bitmap bitmap = BitmapFactory.decodeStream(is);
                    if (bitmap != null) {
                        mIvShow.setImageBitmap(bitmap);
                    }
                } else {
                    mPd.show();
                    new Thread() {
                        public void run() {
                            // 6.下载图片
                            mPd.setMessage("正在载入数据....");
                            userDiskLrucache();
                        };
                    }.start();
                }
            }

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

    }

    private void userDiskLrucache() {
        try {

            String bitMapUrl = "https://raw.githubusercontent.com/pangzaifei/LineChartView/master/LineChartView/effice_picture/a.jpg";
            String key = DiskLrucacheUtils.getKey(bitMapUrl);
            Editor edit = mDiskLrucache.edit(key);
            // 7.从server下载图片
            boolean isSuccess = DiskLrucacheUtils.downloadBitmap(bitMapUrl,
                    edit.newOutputStream(0));
            if (isSuccess) {
                // 8.提交到缓存
                edit.commit();
                // 9.下载成功去展示图片
                Message msg = mHandler.obtainMessage();
                msg.obj = true;
                mHandler.sendMessage(msg);
            } else {
                edit.abort();
            }

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

    @Override
    protected void onPause() {
        try {
            if (mDiskLrucache != null) {
                mDiskLrucache.flush();
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        super.onPause();
    }

    @Override
    protected void onDestroy() {
        try {
            if (mDiskLrucache != null) {

                mDiskLrucache.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        super.onDestroy();
    }
}

使用DiskLrucache自己写的工具类.

package com.pangzaifei.disklrucachedemo.libcore;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

import android.content.Context;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager.NameNotFoundException;
import android.os.Environment;

/**
 * diskLrucache的工具类
 *
 * @author pangzf
 * @date 2014年8月12日 上午10:58:50
 */
public class DiskLrucacheUtils {
    /**
     * 获得缓存文件夹，当sdcard存在的时候使用，sdcard图片缓存。假设sdcard不存在使用data/data下的图片缓存
     *
     * @param context
     * @param uniqueName
     * @return
     */
    public static File getDiskCache(Context context, String uniqueName) {
        String path;
        if (Environment.getExternalStorageDirectory().equals(
                Environment.MEDIA_MOUNTED)) {
            // 存在sdcard
            path = Environment.getExternalStorageDirectory().getPath();
        } else {
            // 不存在sdcard使用手机内存
            path = context.getCacheDir().getPath();
        }
        return new File(path + File.separator + uniqueName);
    }

    /**
     * 获得app版本
     *
     * @param context
     * @return
     * @throws NameNotFoundException
     */
    public static int getAppVersion(Context context)
            throws NameNotFoundException {
        PackageInfo packageInfo = context.getPackageManager().getPackageInfo(
                context.getPackageName(), 0);
        return packageInfo.versionCode;

    }

    /**
     * 将图片url进行md5加密生成一个字符串，由于有的url地址里面存在特殊字符
     *
     * @param urlStr
     * @return
     * @throws NoSuchAlgorithmException
     */
    public static String getKey(String urlStr) throws NoSuchAlgorithmException {
        MessageDigest messageDigest = MessageDigest.getInstance("md5");
        messageDigest.update(urlStr.getBytes());
        return bytesToString(messageDigest.digest());
    }

    /**
     * byte转string
     *
     * @param bytes
     */
    private static String bytesToString(byte[] bytes) {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < bytes.length; i++) {
            String hex = Integer.toHexString(0xFF & bytes[i]);
            if (hex.length() == 1) {
                sb.append(0);
            }
            sb.append(hex);
        }
        return sb.toString();
    }

    /**
     * 下载图片到cache
     *
     * @param imageString
     * @param ops
     * @return
     */
    public static boolean downloadBitmap(String imageString, OutputStream ops) {
        URL url;
        HttpURLConnection conn = null;
        BufferedInputStream bis = null;
        BufferedOutputStream bos = null;
        try {
            url = new URL(imageString);
            conn = (HttpURLConnection) url.openConnection();

            bis = new BufferedInputStream(conn.getInputStream());
            bos = new BufferedOutputStream(ops);

            int b;
            while ((b = bis.read()) != -1) {
                bos.write(b);
            }
            return true;
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (conn != null) {
                    conn.disconnect();
                }
                if (bos != null) {
                    bos.close();
                }
                if (bis != null) {
                    bis.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return false;

    }
}

源代码下载地址

感谢guolin的博客对我的帮助。