将文件（图像）从CacheDir复制到SD卡

void copyFile(File src, File dst) throws IOException {    FileChannel inChannel = new FileInputStream(src).getChannel();    FileChannel outChannel = new FileOutputStream(dst).getChannel();    try {        inChannel.transferTo(0, inChannel.size(), outChannel);    } finally {        if (inChannel != null) inChannel.close();        if (outChannel != null) outChannel.close();    }}