Android FTPClient - retrieveFileStream()总是返回null
Android FTPClient - retrieveFileStream()总是返回null
提问于 2011-11-24 13:12:48
我是Android的新手。我正在尝试使用从ftp服务器下载一个文件到sdcard。InputStream input = client.retrieveFileStream("/“+fileName)行；总是返回null。但是文件在Ftp的位置。请帮助我知道错误在哪里。
我在清单中设置了以下权限: android:name="android.permission.INTERNET“和
我的代码
private static void downLoad(){
FTPClient client = new FTPClient();
FileOutputStream fos = null;
try {
client.connect("ftp.doamin.com");
client.login("8888", "8888");
String filePath = "/mnt/sdcard/download/CheckboxHTML.txt" ;
String fileName = "CheckboxHTML.txt";
fos = new FileOutputStream(filePath);
InputStream input = client.retrieveFileStream("/" + fileName);
byte[] data = new byte[1024];
int count = input.read(data);
while ((count = input.read(data)) != -1) {
fos.write(data, 0, count);
}
fos.close();
if(!client.completePendingCommand()) {
client.logout();
client.disconnect();
System.err.println("File transfer failed.");
}
} catch (SocketException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}谢谢你的时间和兴趣。安娜思。
回答 3
Stack Overflow用户
发布于 2013-06-05 12:20:34
AFAIK。您应该通过调用completePendingCommand()并验证传输确实成功来完成文件传输。也就是说，您需要在fos.clos()下面添加调用函数。
fos.close();
client.completePendingCommand()您还可以考虑这一点，根据FTPClient.retrieveFileStream()的API，方法在无法打开数据连接时返回null，在这种情况下，您应该检查应答代码(例如，getReplyCode()、getReplyString()、getReplyStrings())以查看失败的原因。
Stack Overflow用户
发布于 2012-11-09 10:03:46
File file = new File(Environment.getExternalStorageDirectory() + "/pdf");
if(!file.exists())
file.mkdir(); //directory is created;
try {
ftp = new FTPClient();
ftp.connect("yours ftp URL",21);//don't write ftp://
try {
int reply = ftp.getReplyCode();
if (!FTPReply.isPositiveCompletion(reply)) {
throw new Exception("Connect failed: " + ftp.getReplyString());
}
if (!ftp.login("username","password")) {
throw new Exception("Login failed: " + ftp.getReplyString());
}
try {
ftp.enterLocalPassiveMode();
if (!ftp.setFileType(FTP.BINARY_FILE_TYPE)) {
// Log.e(TAG, "Setting binary file type failed.");
}
transferFile(ftp);
} catch(Exception e) {
// handleThrowable(e);
} finally {
if (!ftp.logout()) {
// Log.e(TAG, "Logout failed.");
}
}
} catch(Exception e) {
// handleThrowable(e);
} finally {
ftp.disconnect();
}
} catch(Exception e) {
// handleThrowable(e);
}
}
private void transferFile(FTPClient ftp) throws Exception {
long fileSize=0;
fileSize = getFileSize(ftp, "nag.pdf");
Log.v("async","fileSize"+fileSize);
if(!(fileSize==0)){
InputStream is = retrieveFileStream(ftp, "nag.pdf");
downloadFile(is, fileSize);
is.close();
}
else
//nosuch files
if (!ftp.completePendingCommand()) {
throw new Exception("Pending command failed: " + ftp.getReplyString());
}
}
private InputStream retrieveFileStream(FTPClient ftp, String filePath)
throws Exception {
InputStream is = ftp.retrieveFileStream(filePath);
int reply = ftp.getReplyCode();
if (is == null
|| (!FTPReply.isPositivePreliminary(reply)
&& !FTPReply.isPositiveCompletion(reply))) {
throw new Exception(ftp.getReplyString());
}
return is;
}
private byte[] downloadFile(InputStream is, long fileSize)
throws Exception {
outputStream os = newFileOutputStream(Environment.getExternalStorageDirectory()
+ "/pdf/nag.pdf");
byte[] buffer = new byte[(int) fileSize];
int readCount;
while( (readCount = is.read(buffer)) > 0) {
os.write(buffer, 0, readCount);
}
Log.i("tag", "buffer = " + buffer);
return buffer; // <-- Here is your file's contents !!!
}
private long getFileSize(FTPClient ftp, String filePath) throws Exception {
long fileSize = 0;
FTPFile[] files = ftp.listFiles(filePath);
if (files.length == 1 && files[0].isFile()) {
fileSize = files[0].getSize();
}
Log.i("tag", "File size = " + fileSize);
return fileSize;
}
}Stack Overflow用户
发布于 2020-03-04 12:49:35
在研究了这个问题并花了几个小时之后，我发现AndroidApacheretrieveFile()和retrieveFileStream有时在FileSize太大的时候不能很好地工作。
确保将正确的TypeFile设置为BinaryFile
mFTPClient.setFileType(FTP.BINARY_FILE_TYPE)；
也不要忘记传入LocalPassiveMode下载命令。
mFTPClient.enterLocalPassiveMode();
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/8257639
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