DiskLruCacheUtil.java

package com.ttj.cache;

import java.io.File;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

import com.ttj.utils.AppUtils;
import com.ttj.utils.FileUtils;

import android.annotation.SuppressLint;
import android.content.Context;
import android.os.Environment;

/**
 * 缓存工具类
 * 
 */

public class DiskLruCacheUtil {

	private static int valueCount = 1;// 同一个key可以对应多少个缓存文件

	private static int maxSize = 10 * 1024 * 1024;// 一个缓存文件最大可以缓存10M

	public static final String CACHE_OBJECT = "object";// 对象缓存目录

	/**
	 * 保存对象缓存
	 * 
	 * @param context
	 * @param ser
	 * @param key
	 */
	public static void saveObject(Context context, Serializable ser, String key) {
		ObjectOutputStream oos = null;
		try {
			DiskLruCache.Editor editor = getDiskLruCacheOutputStream(context,
					CACHE_OBJECT, key);
			if (editor != null) {
				oos = new ObjectOutputStream(editor.newOutputStream(0));
				oos.writeObject(ser);
				oos.flush();
				editor.commit();
			}
		} catch (IOException e) {

			e.printStackTrace();
		} finally {
			FileUtils.closeIO(oos);
		}
	}

	/**
	 * 读取对象缓存
	 * 
	 * @param context
	 * @param key
	 * @return
	 */
	public static Serializable readObject(Context context, String key) {
		ObjectInputStream ois = null;
		try {
			DiskLruCache.Editor editor = getDiskLruCacheOutputStream(context,
					CACHE_OBJECT, key);
			ois = new ObjectInputStream(editor.newInputStream(0));
			return (Serializable) ois.readObject();
		} catch (IOException e) {
			e.printStackTrace();
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} finally {
			FileUtils.closeIO(ois);
		}
		return null;
	}

	/**
	 * 获取DiskLruCache的editor
	 * 
	 * @param context
	 * @param key
	 * @return
	 * @throws IOException
	 */
	public static DiskLruCache.Editor getDiskLruCacheOutputStream(
			Context context, String uniqueName, String key) throws IOException {
		DiskLruCache mDiskLruCache = DiskLruCache.open(
				getDiskCacheDir(context, uniqueName),
				AppUtils.getVersionCode(context), valueCount, maxSize);
		DiskLruCache.Editor editor = mDiskLruCache.edit(hashKeyForDisk(key));
		return editor;
	}

	/**
	 * 获取相应的缓存目录
	 * 
	 * @param context
	 * @param uniqueName
	 * @return
	 */
	@SuppressLint("NewApi")
	public static File getDiskCacheDir(Context context, String uniqueName) {
		String cachePath;
		if (Environment.MEDIA_MOUNTED.equals(Environment
				.getExternalStorageState())
				|| !Environment.isExternalStorageRemovable()) {
			cachePath = context.getExternalCacheDir().getPath();
		} else {
			cachePath = context.getCacheDir().getPath();
		}
		return new File(cachePath + File.separator + uniqueName);
	}

	/**
	 * 传入缓存的key值，以得到相应的MD5值
	 * 
	 * @param key
	 * @return
	 */
	public static String hashKeyForDisk(String key) {
		String cacheKey;
		try {
			final MessageDigest mDigest = MessageDigest.getInstance("MD5");
			mDigest.update(key.getBytes());
			cacheKey = bytesToHexString(mDigest.digest());
		} catch (NoSuchAlgorithmException e) {
			cacheKey = String.valueOf(key.hashCode());
		}
		return cacheKey;
	}

	private static String bytesToHexString(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();
	}
}