java-“连接未打开” FTP Android

每次尝试连接时,都会出现“连接未打开”的异常.当我尝试通过FileZilla或浏览器访问时,服务器运行良好.

我正在使用apache-common-net库.

private Boolean downloadAndSaveFile(String server, int portNumber,
                                    String user, String password, String filename, File localFile)
        throws IOException {
    FTPClient ftp = null;

    try {
        ftp = new FTPClient();
        ftp.connect(server, portNumber);

        ftp.login(user, password);

        ftp.setFileType(FTP.BINARY_FILE_TYPE);

        ftp.enterLocalPassiveMode();

        OutputStream outputStream = null;
        boolean success = false;
        try {
            outputStream = new bufferedoutputstream(new FileOutputStream(
                    localFile));
            success = ftp.retrieveFile(filename, outputStream);
        } finally {
            if (outputStream != null) {
                outputStream.close();
            }
        }

        return success;
    } finally {
        if (ftp != null) {
            ftp.logout();
            ftp.disconnect();
        }
    }
}

实现方式：

 private Boolean buttonDo(String atividade, int groupPosition, int childPosition)  {
    try {
        downloadAndSaveFile(servidor, porta, user, password, filename, filelocation);

    }catch (IOException e) {
        Toast.makeText(_context,e.getMessage(),Toast.LENGTH_SHORT).show();

    }
    return false;
}

日志：

java.io.IOException: Connection is not open
 at org.apache.commons.net.ftp.FTP.sendCommand(FTP.java:514)
 at org.apache.commons.net.ftp.FTP.sendCommand(FTP.java:648)
 at org.apache.commons.net.ftp.FTP.sendCommand(FTP.java:622)
 at org.apache.commons.net.ftp.FTP.quit(FTP.java:904)
 at org.apache.commons.net.ftp.FTPClient.logout(FTPClient.java:1148)
 at com.joaobernardos.joaobernardo.gave.expandablelistadapter.downloadAndSaveFile(expandablelistadapter.java:124)
 at com.joaobernardos.joaobernardo.gave.expandablelistadapter.buttonDo(expandablelistadapter.java:198)
 at com.joaobernardos.joaobernardo.gave.expandablelistadapter.access$200(expandablelistadapter.java:34)
 at com.joaobernardos.joaobernardo.gave.expandablelistadapter$1.onClick(expandablelistadapter.java:241)
 at android.view.View.performClick(View.java:4756)
 at android.view.View$PerformClick.run(View.java:19761)
 at android.os.Handler.handleCallback(Handler.java:739)
 at android.os.Handler.dispatchMessage(Handler.java:95)
 at android.os.Looper.loop(Looper.java:135)
 at android.app.ActivityThread.main(ActivityThread.java:5253)
 at java.lang.reflect.Method.invoke(Native Method)
 at java.lang.reflect.Method.invoke(Method.java:372)
 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

因此,我去探索FTP.class并发现了导致异常的原因：

 public int sendCommand(String command, String args) throws IOException {
    if(this._controlOutput_ == null) {
        throw new IOException("Connection is not open");
    } else {
        String message = this.__buildMessage(command, args);
        this.__send(message);
        this.fireCommandSent(command, message);
        this.__getReply();
        return this._replyCode;
    }
}

我没有使用工作线程.我是不是该？我该如何实施？

解决方法:

当您“尝试连接”时,您没有得到例外.当您注销时,您会得到它.

我猜,实际发生的是try块中的代码抛出了一个异常,而没有实际连接.然后,您尝试注销finally块,这会引发异常,因为您从未登录.

删除ftp.logout()和ftp.disconnect()以避免吞下主要异常,以查看何时是您的实际问题.

当您在GUI线程上做网络工作时,很可能是实际问题.主要例外可以是networkonmainthreadExeption.
查看How do I fix android.os.NetworkOnMainThreadException?

java-“连接未打开” FTP Android

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