Android缓存Cache学习

Android缓存Cache学习

项目中需要用到缓存，我使用的是文件缓存，这里简单总结下：

主要思路是封装一个缓存对象，将每个界面需要缓存的数据作为缓存对象的属性，将缓存对象以PageCache缓存到文件。

缓存对象类：

//封装缓存数据对象
public class PageCache implements Serializable {
	private static final long serialVersionUID = 3405510521707227897L;
	public static final String PAGE_KEY = "page.key";


	// 缓存数据是集合
	private List<BenqunItem> benqunList; 

	
	public List<BenqunItem> getBenqunList() {
		return benqunList;
	}

	public void setBenqunList(List<BenqunItem> benqunList) {
		this.benqunList = benqunList;
	}

缓存工具类：

public class DataFileCache {
	public static String FUJIN_CACHE_NAME = "A"; // 附近的人缓存目录
	public static String BENQUN_CACHE_NAME = "B"; // 社群缓存目录
	public static String BENYOU_CACHE_NAME = "C"; // 好友数据缓存目录
	public static String USER_CACHE_NAME = "D"; // 个人页面缓存

	public static final String CACHDIR = File.separator + "benben"
			+ File.separator + "cache" + File.separator;// 缓存根目录

	private static final String Suffix = ".benben";// 缓存文件后缀名
	private static final int FREE_SD_SPACE_NEEDED_TO_CACHE = 1;// 缓存空间大于1M才能进行缓存
	private int MB = 1024 * 1024;
	private String folder = "";

	public static final String Favorit_CACHE_NAME = "Favorit";
	public static final String LOG_CACHE_NAME = "Log"; // 日志文件目录
	public static final int Favorit_Key = 0x100;
	public static final String Category_CACHE_NAME = "Category";
	public static final int Category_Key = 0x101;//

	private Context mContext;

	/**
	 * @param folder
	 *            缓存目录文件夹
	 * */
	public DataFileCache(Context context, String folder) {
		this.folder = folder;
		this.mContext = context;
	}

	/**
	 * 缓存数据
	 * 
	 * @param name
	 *            缓存文件名
	 * @param o
	 *            需要缓存的对象
	 * */
	public boolean saveFile(String name, Object o) {
		// 判断sdcard上的空间
		if (FREE_SD_SPACE_NEEDED_TO_CACHE > freeSpaceOnSd()) {
			// SD空间不足
			return false;
		}
		String value = BaseHelper.object2String(o);
		String filename = convertUrlToFileName(name);
		String dir = getDirectory();
		File file = new File(dir + File.separator + filename);
		OutputStream outStream = null;
		try {
			if (file.exists()) {
				file.delete();
			}
			file.createNewFile();
			outStream = new FileOutputStream(file);
			outStream.write(value.getBytes());
			return true;
		} catch (Exception e) {
			e.printStackTrace();
			return false;
		} finally {
			if (outStream != null) {
				try {
					outStream.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
	}

	/**
	 * 保存日志文件
	 * 
	 * @param name
	 * @param obj
	 */
	public void saveLogFile(String name, String obj) {
		// 判断sdcard上的空间
		if (FREE_SD_SPACE_NEEDED_TO_CACHE > freeSpaceOnSd()) {
			// SD空间不足
			return;
		}
		String filename = convertUrlToFileName(name);
		String dir = getDirectory();
		FileWriter fileWriter;
		try {
			fileWriter = new FileWriter(dir + File.separator + filename, true);
			fileWriter.write(obj);
			fileWriter.close();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

	/**
	 * 判断文件日志文件
	 * 
	 * @param name
	 * @return
	 */
	public boolean isExist(String name) {
		final String path = getDirectory() + File.separator
				+ convertUrlToFileName(name);
		File file = new File(path);
		return file.exists();
	}

	/**
	 * 读取缓存文件，并返回数据
	 * 
	 * @param name
	 *            缓存文件名
	 * */
	public Object openFile(String name) {
		Object o = null;
		final String path = getDirectory() + File.separator
				+ convertUrlToFileName(name);
		File file = new File(path);
		if (file.exists()) {
			try {
				FileInputStream inputStream = new FileInputStream(file);
				BufferedReader br = new BufferedReader(new InputStreamReader(
						inputStream));
				StringBuilder sb = new StringBuilder("");
				String line = null;
				while ((line = br.readLine()) != null) {
					sb.append(line);
				}
				String value = sb.toString();
				if (!"".equals(value)) {
					byte[] bytes = Base64.decode(value);
					ByteArrayInputStream navBais = new ByteArrayInputStream(
							bytes);
					ObjectInputStream navOis = new ObjectInputStream(navBais);
					o = (Object) navOis.readObject();
					navBais.close();
					navOis.close();
				}
			} catch (Exception e) {
				e.printStackTrace();
				return null;
			}
		}
		return o;
	}

	/**
	 * 清空缓存目录下的文件
	 * */
	public boolean clear() {
		File dir = new File(getDirectory());
		File[] files = dir.listFiles();
		if (files == null) {
			return true;
		}
		if (!Environment.getExternalStorageState().equals(
				Environment.MEDIA_MOUNTED)) {
			return false;
		}
		for (int i = 0; i < files.length; i++) {
			files[i].delete();
		}
		dir.delete();
		return true;
	}

	/**
	 * 清空商品分类缓存文件
	 * */
	public boolean clearCategory() {
		final String path = getDirectory();
		File dir = new File(path);
		try {
			File[] files = dir.listFiles();
			if (!Environment.getExternalStorageState().equals(
					Environment.MEDIA_MOUNTED)) {
				return false;
			}
			for (int i = 0; i < files.length; i++) {
				files[i].delete();
			}
			dir.delete();
		} catch (Exception e) {
			// TODO: handle exception
			return false;
		}
		return true;
	}

	/**
	 * 计算sdcard上的剩余空间
	 * 
	 * @return
	 */
	private int freeSpaceOnSd() {
		StatFs stat = new StatFs(Environment.getExternalStorageDirectory()
				.getPath());
		double sdFreeMB = ((double) stat.getAvailableBlocks() * (double) stat
				.getBlockSize()) / MB;
		return (int) sdFreeMB;
	}

	/**
	 * 转成统一的文件名
	 * */
	private String convertUrlToFileName(String fileName) {
		return BaseHelper.delSignBlank(fileName) + Suffix;
	}

	/**
	 * 获得缓存目录 根据用户id获取当前用户的缓存目录 不同用户缓存目录是不同的
	 * */
	private String getDirectory() {
		String dir = "";

		LoginBean loginBean = SharedPreferencesUtils.getObject(mContext,
				Preferences.LOGIN_RESPONSE, LoginBean.class);// 获取当前登录用户id
		if (loginBean != null && loginBean.getPersonId() != null) {
			// 缓存路径，SD卡+缓存文件名+当前用户+缓存内容的文件名
			dir = getSDPath() + CACHDIR + loginBean.getPersonId()
					+ File.separator + folder;
		} else {
			dir = getSDPath() + CACHDIR + "default" + File.separator + folder;
		}

		try {
			File file = new File(dir);
			if (!file.exists()) {
				file.mkdirs();
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
		return dir;
	}

	/**
	 * 取SD卡路径不带/
	 * */
	private String getSDPath() {
		File sdDir = null;
		boolean sdCardExist = Environment.getExternalStorageState().equals(
				android.os.Environment.MEDIA_MOUNTED); // 判断sd卡是否存在
		if (sdCardExist) {
			sdDir = Environment.getExternalStorageDirectory();// 获取跟目录
		}
		if (sdDir != null) {
			return sdDir.toString();
		} else {
			return "";
		}
	}

	public boolean saveTxt(String name, String value) {
		// 判断sdcard上的空间
		if (FREE_SD_SPACE_NEEDED_TO_CACHE > freeSpaceOnSd()) {
			// SD空间不足
			return false;
		}
		String filename = name + ".txt";
		String dir = getDirectory();
		File file = new File(dir + File.separator + filename);
		OutputStream outStream = null;
		try {
			if (file.exists()) {
				file.delete();
			}
			file.createNewFile();
			outStream = new FileOutputStream(file);
			outStream.write(value.getBytes());
			return true;
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			if (outStream != null) {
				try {
					outStream.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
		return false;
	}

	/**
	 * 读取缓存文件，并返回数据
	 * 
	 * @param name
	 *            读取缓存文件的文件名
	 * */
	public String openTxt(String name) {
		final String path = getDirectory() + File.separator + name + ".txt";
		File file = new File(path);
		if (file.exists()) {
			try {
				FileInputStream inputStream = new FileInputStream(file);
				BufferedReader br = new BufferedReader(new InputStreamReader(
						inputStream));
				StringBuilder sb = new StringBuilder("");
				String line = null;
				while ((line = br.readLine()) != null) {
					sb.append(line);
				}
				String value = sb.toString();
				return value;
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
		return "";
	}
}

Activity调用：

//缓存文件名，这里使用类名

private final static String TAG = ShequFragment.class.getSimpleName();

1，实例化缓存工具类

DataFileCache dataFileCache = new DataFileCache(getActivity(),
DataFileCache.BENQUN_CACHE_NAME);

2，获取数据后缓存

// 缓存
<pre name="code" class="java">
 <pre name="code" class="java">PageCache <span style="font-family: Arial, Helvetica, sans-serif;">page = new PageCache ();</span>

page.setBenqunList(allata);dataFileCache.saveFile(TAG, page);

3,获取缓存数据

<pre name="code" class="java"><pre name="code" class="java">//获取缓存数据							
Object obj = dataFileCache.openFile(TAG);
		if (obj != null) {
			PageCache page = (PageCache) obj;
			allata = page.getBenqunList();
			mAdapter.addList(allata);
			mAdapter.notifyDataSetChanged();
		} else {

<span style="white-space:pre">			</span>//缓存没有数据，网络获取
			getAllBBSClassList(true);

		}