延迟删除临时文件
下载文件完毕后删除临时文件：

public InputStream getInputStream() {InputStream is = null;try {is = new FileInputStream(file);} catch (FileNotFoundException e) {e.printStackTrace();}Thread t = new Thread(new Runnable() {public void run() {try {// 线程睡30秒Thread.sleep(30000);} catch (InterruptedException e) {e.printStackTrace();}// 删除临时文件file.delete();}});t.start();return is;}