I can not access to FTP in Android
<p>I am working on a project. My project first step connect to ftp. I read documentation and searched in stackoverflow but i did not find a solution. 
I am beginner for android developer. When run application i saw fatal errors below LogCat and java files.How can i fix that please help me this project very important for me.</p>

<p>logcat:</p>

<pre><code>11-03 04:27:37.640: E/AndroidRuntime(330): FATAL EXCEPTION: main
11-03 04:27:37.640: E/AndroidRuntime(330): java.lang.NoClassDefFoundError: org.apache.commons.net.ftp.FTPClient
11-03 04:27:37.640: E/AndroidRuntime(330):  at com.example.cka.MainActivity$1.onClick(MainActivity.java:33)
11-03 04:27:37.640: E/AndroidRuntime(330):  at android.view.View.performClick(View.java:2408)
11-03 04:27:37.640: E/AndroidRuntime(330):  at android.view.View$PerformClick.run(View.java:8816)
11-03 04:27:37.640: E/AndroidRuntime(330):  at android.os.Handler.handleCallback(Handler.java:587)
11-03 04:27:37.640: E/AndroidRuntime(330):  at android.os.Handler.dispatchMessage(Handler.java:92)
11-03 04:27:37.640: E/AndroidRuntime(330):  at android.os.Looper.loop(Looper.java:123)
11-03 04:27:37.640: E/AndroidRuntime(330):  at android.app.ActivityThread.main(ActivityThread.java:4627)
11-03 04:27:37.640: E/AndroidRuntime(330):  at java.lang.reflect.Method.invokeNative(Native Method)
11-03 04:27:37.640: E/AndroidRuntime(330):  at java.lang.reflect.Method.invoke(Method.java:521)
11-03 04:27:37.640: E/AndroidRuntime(330):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
11-03 04:27:37.640: E/AndroidRuntime(330):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
11-03 04:27:37.640: E/AndroidRuntime(330):  at dalvik.system.NativeStart.main(Native Method)
11-03 04:27:40.810: I/Process(330): Sending signal. PID: 330 SIG: 9
</code></pre>

<p>--</p>

<p>main activity:</p>

<pre><code>    Button btn = (Button) findViewById(R.id.button1);
    final TextView tv = (TextView) findViewById(R.id.textView1);        
    btn.setOnClickListener(new View.OnClickListener() {         
    public void onClick(View v) {
        // TODO Auto-generated method stub
        core f = new core();
        f.mFTPClient = new FTPClient();
        f.ftpConnect("**.***.***.**", "****", "****", 21);
        try {
            tv.setText(f.ftpStatus());
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    });
</code></pre>

<p>--</p>

<p>core.java</p>

<pre><code>package com.example.cka;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import org.apache.commons.net.ftp.*;
import android.util.Log;

public class core {


    private static final String TAG = null;
    public FTPClient mFTPClient = null;

    public boolean ftpConnect(String host, String username,String password, int port){

        try {
            mFTPClient = new FTPClient();
            // connecting to the host
            mFTPClient.connect(host, port);

            if (FTPReply.isPositiveCompletion(mFTPClient.getReplyCode())) {
            boolean status = mFTPClient.login(username, password);

            mFTPClient.setFileType(FTP.BINARY_FILE_TYPE);
            mFTPClient.enterLocalPassiveMode();

            return status;
            }
        }    

        catch(Exception e) {
            Log.d(TAG, "Error: could not connect to host " + host );
        }

        return false;
    }



    public boolean ftpDisconnect()
    {
        try {
            mFTPClient.logout();
            mFTPClient.disconnect();
            return true;
        } catch (Exception e) {
            Log.d(TAG, "Error occurred while disconnecting from ftp server.");
        }

        return false;
    }

    public String ftpStatus() throws IOException{

            String status = mFTPClient.getStatus();
            return status;
    }       
}
</code></pre>
