android编程实现图片库的封装方法

public class PictureLibrary { /*  * 图片库的操作  */ File file; URL url; HttpURLConnection conn; InputStream is; FileOutputStream fos; private Lock lock = new ReentrantLock(); private Condition downFile = lock.newCondition(); // 通过URL将数据下载到本地操作 private String toLocalFile(String strURL) {  String fileName = Utils.getFileName(strURL);  String path = Environment.getExternalStorageDirectory() + "/"    + EcologicalTourism.FILE_PATH + "/images/" + fileName;  return path; } // 通过URL将数据下载到本地临时文件中 private String toLocalFileTemp(String strURL) {  String s = Utils.getFileName(strURL);  String fileName = s+"temp";  String path_url = Environment.getExternalStorageDirectory() + "/"    + EcologicalTourism.FILE_PATH + "/tempimages/" + fileName;  return path_url; } /*  * 保存图片到本地，并返回本地url（此函数是阻塞的）  * main  * @参数：strURL，参数为图片的URL.返回值：该图片在本地SD卡暂存的位置  * 函数的工作是负责将图片从互联网上取得，存在本地存储中，并返回本地存储的文件路径，供调用者直接使用。如果文件已经存在本地，直接返回  * 如果文件未在本地，则直接从服务器下载，函数阻塞。  */ public String getReadSD(String strURL) {  Log.i("test", "拿到网络的地址是：" + strURL);  String strLocalFile = toLocalFile(strURL); //k：把服务器URL转换为本地URL  String strLocalFileTemp = toLocalFileTemp(strURL); //k：把服务器URL转换为本地临时URL  while (true) {   File file = new File(strLocalFile);   Log.i("test", "本地文件是：" + strLocalFile);   File tfile = new File(strLocalFileTemp);   Log.i("test", "临时文件是：" + strLocalFileTemp);   // 1上锁   lock.lock();   if (file.exists()) {    // 2if 本地文件存在    // 解锁    // 返回本地路径    lock.unlock();    Log.i("test", "返回本地路径：" + file);    return strLocalFile;   } else if (tfile.exists()) {    // if 对应的暂存文件存在    // 解锁    lock.unlock();    try {     // 睡眠     downFile.await();    } catch (Exception e) {      e.printStackTrace();     Log.i("test", "e 出现了异常1" + e);    }   } else {    try {     // 创建对应的暂存文件     tfile.createNewFile();    } catch (IOException e) {     Log.i("test", "e 出现了异常2" + e);    }    // 解锁    lock.unlock();    // 下载文件内容到暂存文件中    downURL2(strURL, strLocalFile);    // 上锁    lock.lock();    // 修改暂存文件名字为本地文件名    tfile.renameTo(file);    // 解锁    lock.unlock();   }  } } private void downURL2(String strURL, String strLocalFileTemp) {  // TODO Auto-generated method stub  URL url;  try {   url = new URL(strURL);   HttpURLConnection conn = (HttpURLConnection) url.openConnection();   conn.setConnectTimeout(5000);   conn.setRequestMethod("GET");   conn.setDoInput(true);   if (conn.getResponseCode() == 200) {     InputStream is = conn.getInputStream();     FileOutputStream fos = new FileOutputStream(strLocalFileTemp);     byte[] buffer = new byte[1024];     int len = 0;     while ((len = is.read(buffer)) != -1) {       fos.write(buffer, 0, len);     }     is.close();     fos.close();     // 返回一个URI对象   }  } catch (MalformedURLException e) {   // TODO Auto-generated catch block   e.printStackTrace();  } catch (ProtocolException e) {   // TODO Auto-generated catch block   e.printStackTrace();  } catch (IOException e) {   // TODO Auto-generated catch block   e.printStackTrace();  } } /*  * 阻塞式下载url到文件 toFile中  */ private boolean downURL(String strURL, String toFile) {  URL url;  try {   url = new URL(strURL);   HttpURLConnection httpUrl = (HttpURLConnection) url     .openConnection();   httpUrl.setRequestMethod("GET");   int fileSize = httpUrl.getContentLength();// 文件大小   httpUrl.disconnect();// 关闭连接   int threadSize = 6;// 默认设置6个线程   threadSize = fileSize % threadSize == 0 ? threadSize     : threadSize + 1;   int currentSize = fileSize / threadSize; // 每条线程下载大小   String dowloadir = Environment.getExternalStorageDirectory() + "/"     + EcologicalTourism.FILE_PATH + "/images/";   File dir = new File(dowloadir);   if (!dir.exists()) {    dir.mkdirs();   }   File file = new File(dir, toFile);   RandomAccessFile randomFile = new RandomAccessFile(file, "rw");   randomFile.setLength(fileSize);// 指定 file 文件的大小   for (int i = 0; i < threadSize; i++) {    int startposition = i * currentSize;// 每条线程开始写入文件的位置    RandomAccessFile threadFile = new RandomAccessFile(file, "rw");    Log.i("syso", "toFile的内容是：" + toFile);    threadFile.seek(startposition);    new DownLoadThread(i, currentSize, threadFile, startposition,      url).start();   }  } catch (Exception e) {   e.printStackTrace();   Log.i("syso", "download下载失败" + e);  }  return true; } /**  * 实现线程下载  *   */ private static class DownLoadThread extends Thread {  @SuppressWarnings("unused")  private int threadId;// 线程编号  private int currentSize;// 每条线程的大小  private RandomAccessFile threadFile; // 每条线程 要写入文件类  private int startposition;// 每条线程开始写入文件的位置  private URL url; //网络地址  public DownLoadThread(int threadId, int currentSize,    RandomAccessFile threadFile, int startposition, URL url) {   this.threadId = threadId;   this.currentSize = currentSize;   this.threadFile = threadFile;   this.startposition = startposition;   this.url = url;  }  public void run() {   try {    HttpURLConnection httpUrl = (HttpURLConnection) url      .openConnection();    httpUrl.setRequestMethod("GET");    httpUrl.setRequestProperty("range", "bytes=" + startposition      + "-");// 指定服务器的位置    InputStream is = httpUrl.getInputStream();    byte[] data = new byte[1024];    int len = -1;    int threadFileSize = 0;    while ((threadFileSize < currentSize)      && ((len = is.read(data)) != -1)) {     threadFile.write(data, 0, len);     threadFileSize += len;    }    httpUrl.disconnect();    is.close();   } catch (Exception e) {    e.printStackTrace();   }  } } /** * 从本缓存中获取图片 */ public Bitmap getBitmapFromCache(String imageURL) { // String bitmapName = imageURL.substring(imageURL.lastIndexOf("/") + 1);   String bitmapName = Utils.getFileName(imageURL);  File cacheDir = new File(Environment.getExternalStorageDirectory() + "/"    + EcologicalTourism.FILE_PATH + "/images/");  File[] cacheFiles = cacheDir.listFiles();  int i = 0;  if(null!=cacheFiles){   for(; i<cacheFiles.length;i++){    if(bitmapName.equals(cacheFiles[i].getName())){     break;    }   }   if(i < cacheFiles.length)   {    return BitmapFactory.decodeFile(Environment.getExternalStorageDirectory() + "/"      + EcologicalTourism.FILE_PATH + "/images/" + bitmapName);   }  }  return null; }