android文件缓存管理
缓存类 :
public class ConfigCache { private static final String TAG = ConfigCache.class.getName(); public static final int CONFIG_CACHE_MOBILE_TIMEOUT = 3600000; //1 hour public static final int CONFIG_CACHE_WIFI_TIMEOUT = 300000; //5 minute public static String getUrlCache(String url) { if (url == null) { return null; } String result = null; File file = new File(AppApplication.mSdcardDataDir + "/" + getCacheDecodeString(url)); if (file.exists() && file.isFile()) { long expiredTime = System.currentTimeMillis() - file.lastModified(); Log.d(TAG, file.getAbsolutePath() + " expiredTime:" + expiredTime/60000 + "min"); //1. in case the system time is incorrect (the time is turn back long ago) //2. when the network is invalid, you can only read the cache if (AppApplication.mNetWorkState != NetworkUtils.NETWORN_NONE && expiredTime < 0) { return null; } if(AppApplication.mNetWorkState == NetworkUtils.NETWORN_WIFI && expiredTime > CONFIG_CACHE_WIFI_TIMEOUT) { return null; } else if (AppApplication.mNetWorkState == NetworkUtils.NETWORN_MOBILE && expiredTime > CONFIG_CACHE_MOBILE_TIMEOUT) { return null; } try { result = FileUtils.readTextFile(file); } catch (IOException e) { e.printStackTrace(); } } return result; } public static void setUrlCache(String data, String url) { File file = new File(AppApplication.mSdcardDataDir + "/" + getCacheDecodeString(url)); try { //创建缓存数据到磁盘，就是创建文件 FileUtils.writeTextFile(file, data); } catch (IOException e) { Log.d(TAG, "write " + file.getAbsolutePath() + " data failed!"); e.printStackTrace(); } } public static String getCacheDecodeString(String url) { //1. 处理特殊字符 //2. 去除后缀名带来的文件浏览器的视图凌乱(特别是图片更需要如此类似处理，否则有的手机打开图库，全是我们的缓存图片) if (url != null) { return url.replaceAll("[.:/,%?&=]", "+").replaceAll("[+]+", "+"); } return null; } }
用法 :
void getConfig(){ //首先尝试读取缓存 String cacheConfigString = ConfigCache.getUrlCache(CONFIG_URL); //根据结果判定是读取缓存，还是重新读取 if (cacheConfigString != null) { // showConfig(cacheConfigString); //后面可以是UI更新，仅供参考 } else { //如果缓存结果是空，说明需要重新加载 //缓存为空的原因可能是1.无缓存;2. 缓存过期;3.读取缓存出错 AsyncHttpClient client = new AsyncHttpClient(); client.get(CONFIG_URL, new AsyncHttpResponseHandler(){ @Override public void onSuccess(String result){ //成功下载，则保存到本地作为后面缓存文件 ConfigCache.setUrlCache(result, CONFIG_URL); //后面可以是UI更新，仅供参考 // showConfig(result); } @Override public void onFailure(Throwable arg0) { //根据失败原因，考虑是显示加载失败，还是再读取缓存 } }); } }
相关的工具类 :
/** * 文件处理工具类 * * @author naibo-liao * @时间： 2013-1-4下午03:13:08 */ public class FileUtils { public static final long B = 1; public static final long KB = B * 1024; public static final long MB = KB * 1024; public static final long GB = MB * 1024; private static final int BUFFER = 8192; /** * 格式化文件大小<b> 带有单位 * * @param size * @return */ public static String formatFileSize(long size) { StringBuilder sb = new StringBuilder(); String u = null; double tmpSize = 0; if (size < KB) { sb.append(size).append("B"); return sb.toString(); } else if (size < MB) { tmpSize = getSize(size, KB); u = "KB"; } else if (size < GB) { tmpSize = getSize(size, MB); u = "MB"; } else { tmpSize = getSize(size, GB); u = "GB"; } return sb.append(twodot(tmpSize)).append(u).toString(); } /** * 保留两位小数 * * @param d * @return */ public static String twodot(double d) { return String.format("%.2f", d); } public static double getSize(long size, long u) { return (double) size / (double) u; } /** * sd卡挂载且可用 * * @return */ public static boolean isSdCardMounted() { return android.os.Environment.getExternalStorageState().equals( android.os.Environment.MEDIA_MOUNTED); } /** * 递归创建文件目录 * * @param path * */ public static void CreateDir(String path) { if (!isSdCardMounted()) return; File file = new File(path); if (!file.exists()) { try { file.mkdirs(); } catch (Exception e) { Log.e("hulutan", "error on creat dirs:" + e.getStackTrace()); } } } /** * 读取文件 * * @param file * @return * @throws IOException */ public static String readTextFile(File file) throws IOException { String text = null; InputStream is = null; try { is = new FileInputStream(file); text = readTextInputStream(is);; } finally { if (is != null) { is.close(); } } return text; } /** * 从流中读取文件 * * @param is * @return * @throws IOException */ public static String readTextInputStream(InputStream is) throws IOException { StringBuffer strbuffer = new StringBuffer(); String line; BufferedReader reader = null; try { reader = new BufferedReader(new InputStreamReader(is)); while ((line = reader.readLine()) != null) { strbuffer.append(line).append("\r\n"); } } finally { if (reader != null) { reader.close(); } } return strbuffer.toString(); } /** * 将文本内容写入文件 * * @param file * @param str * @throws IOException */ public static void writeTextFile(File file, String str) throws IOException { DataOutputStream out = null; try { out = new DataOutputStream(new FileOutputStream(file)); out.write(str.getBytes()); } finally { if (out != null) { out.close(); } } } /** * 将Bitmap保存本地JPG图片 * @param url * @return * @throws IOException */ public static String saveBitmap2File(String url) throws IOException { BufferedInputStream inBuff = null; BufferedOutputStream outBuff = null; SimpleDateFormat sf = new SimpleDateFormat("yyyy_MM_dd_HH_mm_ss"); String timeStamp = sf.format(new Date()); File targetFile = new File(Constants.ENVIROMENT_DIR_SAVE, timeStamp + ".jpg"); File oldfile = ImageLoader.getInstance().getDiscCache().get(url); try { inBuff = new BufferedInputStream(new FileInputStream(oldfile)); outBuff = new BufferedOutputStream(new FileOutputStream(targetFile)); byte[] buffer = new byte[BUFFER]; int length; while ((length = inBuff.read(buffer)) != -1) { outBuff.write(buffer, 0, length); } outBuff.flush(); return targetFile.getPath(); } catch (Exception e) { } finally { if (inBuff != null) { inBuff.close(); } if (outBuff != null) { outBuff.close(); } } return targetFile.getPath(); } /** * 读取表情配置文件 * * @param context * @return */ public static List<String> getEmojiFile(Context context) { try { List<String> list = new ArrayList<String>(); InputStream in = context.getResources().getAssets().open("emoji");// 文件名字为rose.txt BufferedReader br = new BufferedReader(new InputStreamReader(in, "UTF-8")); String str = null; while ((str = br.readLine()) != null) { list.add(str); } return list; } catch (IOException e) { e.printStackTrace(); } return null; } /** * 获取一个文件夹大小 * * @param f * @return * @throws Exception */ public static long getFileSize(File f) { long size = 0; File flist[] = f.listFiles(); for (int i = 0; i < flist.length; i++) { if (flist.isDirectory()) { size = size + getFileSize(flist); } else { size = size + flist.length(); } } return size; } /** * 删除文件 * * @param file */ public static void deleteFile(File file) { if (file.exists()) { // 判断文件是否存在 if (file.isFile()) { // 判断是否是文件 file.delete(); // delete()方法 你应该知道 是删除的意思; } else if (file.isDirectory()) { // 否则如果它是一个目录 File files[] = file.listFiles(); // 声明目录下所有的文件 files[]; for (int i = 0; i < files.length; i++) { // 遍历目录下所有的文件 deleteFile(files); // 把每个文件 用这个方法进行迭代 } } file.delete(); } } }
