Приложение Android подключается к FTP-серверу на Java

Я пытаюсь создать приложение для Android с возможностью подключения к указанному FTP-серверу на Java. Операция подключения была выполнена в FTPconnection class, а сетевой вызов FTP был отделен от основного потока через FtpTask реализация класса.

Экспериментальная реализация

• Название проекта: FTPConnectionTest

• FTPconnection реализация класса

  package com.example.ftpconnectiontest;
  
  import android.util.Log;
  
  import java.io.IOException;
  import java.net.InetAddress;
  import java.net.SocketException;
  import java.net.UnknownHostException;
  
  import org.apache.commons.net.SocketClient;
  import org.apache.commons.net.ftp.FTP;
  import org.apache.commons.net.ftp.FTPClient;
  import org.apache.commons.net.ftp.FTPReply;
  
  public class FTPconnection {
  
      private static final String FTPHostName = "Hostname";
      private static final int FTPPort = 21;
      private static final String FTPUsername = "Username";
      private static final String FTPPassword = "Password";
  
      public FTPconnection()
      {
  
      }
  
      public FTPClient connectftp()
      {
          //  Reference: https://stackoverflow.com/a/8761268/6667035
          FTPClient ftp = new FTPClient();
          try {
              //  Reference: https://stackoverflow.com/a/55950845/6667035
              //  The argument of `FTPClient.connect` method is hostname, not URL.
              ftp.connect(FTPHostName, FTPPort);
              boolean status = ftp.login(FTPUsername, FTPPassword);
              if (status)
              {
                  ftp.enterLocalPassiveMode();
                  ftp.setFileType(FTP.BINARY_FILE_TYPE);
                  ftp.sendCommand("OPTS UTF8 ON");
              }
              System.out.println("status : " + ftp.getStatus());
          } catch (UnknownHostException ex) {
              ex.printStackTrace();
          } catch (SocketException en) {
              en.printStackTrace();
          } catch (IOException e) {
              e.printStackTrace();
          }
          return ftp;
      }
  }
  

• FtpTask реализация класса

  //  AsyncTask must be subclassed to be used. The subclass will override at least one method
  //  `doInBackground(Params...)`, and most often will override a second one `onPostExecute(Result)`
  //  Reference: https://developer.android.com/reference/android/os/AsyncTask?authuser=4
  //  Reference: https://stackoverflow.com/a/12447497/6667035
  private class FtpTask extends AsyncTask<Void, Void, FTPClient> {
      //  `doInBackground` invoked on the background thread immediately after `onPreExecute()`
      //  finishes executing. This step is used to perform background computation
      //  that can take a long time. The parameters of the asynchronous task are
      //  passed to this step. The result of the computation must be returned by
      //  this step and will be passed back to the last step. This step can also use
      //  `publishProgress(Progress...)` to publish one or more units of progress.
      //  These values are published on the UI thread, in the `onProgressUpdate(Progress...)`
      //  step.
      protected FTPClient doInBackground(Void... args) {
          FTPconnection ftpConnect = new FTPconnection();
          FTPClient ftp = ftpConnect.connectftp();
          return ftp;
      }
  
      //  `onPostExecute` invoked on the UI thread after the background computation finishes.
      //  The result of the background computation is passed to this step as
      //  a parameter.
      protected void onPostExecute(FTPClient result) {
          Log.v("FTPTask","FTP connection complete");
          ftpClient = result;
          //Where ftpClient is a instance variable in the main activity
          Log.v("Boolean.toString(ftpClient.isConnected())", Boolean.toString(ftpClient.isConnected()));
          ShowToast(Boolean.toString(ftpClient.isConnected()), Toast.LENGTH_SHORT);
      }
  }
  

• Настройка разрешений пользователя

  <uses-permission android:name="android.permission.INTERNET" />
  <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
  <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
  

• AndroidManifest.xml

  <?xml version="1.0" encoding="utf-8"?>
  <manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.example.ftpconnectiontest">
  
      <application
          android:allowBackup="true"
          android:icon="@mipmap/ic_launcher"
          android:label="@string/app_name"
          android:roundIcon="@mipmap/ic_launcher_round"
          android:supportsRtl="true"
          android:theme="@style/Theme.FTPConnectionTest">
          <activity
              android:name=".MainActivity"
              android:exported="true">
              <intent-filter>
                  <action android:name="android.intent.action.MAIN" />
  
                  <category android:name="android.intent.category.LAUNCHER" />
              </intent-filter>
          </activity>
      </application>
      <uses-permission android:name="android.permission.INTERNET" />
      <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
      <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
  </manifest>
  

• build.gradle

  plugins {
      id 'com.android.application'
  }
  
  android {
      compileSdk 30
  
      defaultConfig {
          applicationId "com.example.ftpconnectiontest"
          minSdk 26
          targetSdk 30
          versionCode 1
          versionName "1.0"
  
          testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
      }
  
      buildTypes {
          release {
              minifyEnabled false
              proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
          }
      }
      compileOptions {
          sourceCompatibility JavaVersion.VERSION_1_8
          targetCompatibility JavaVersion.VERSION_1_8
      }
  }
  
  dependencies {
      implementation fileTree(include: ['*.jar'], dir: 'libs')
      // https://mvnrepository.com/artifact/commons-net/commons-net
      implementation group: 'commons-net', name: 'commons-net', version: '20030805.205232'
      implementation 'androidx.appcompat:appcompat:1.2.0'
      implementation 'com.google.android.material:material:1.3.0'
      implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
      testImplementation 'junit:junit:4.13.2'
      androidTestImplementation 'androidx.test.ext:junit:1.1.2'
      androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'
  }
  

Полный код тестирования

MainActivity.java выполнение:

package com.example.ftpconnectiontest;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Context;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.widget.Toast;

import org.apache.commons.net.ftp.FTPClient;

public class MainActivity extends AppCompatActivity {

    private FTPClient ftpClient;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        new FtpTask().execute();
    }

    void ShowToast(String Text, int Duration)
    {
        Context context = getApplicationContext();
        CharSequence text = Text;
        int duration = Duration;

        Toast toast = Toast.makeText(context, text, duration);
        toast.show();
    }

    //  AsyncTask must be subclassed to be used. The subclass will override at least one method
    //  `doInBackground(Params...)`, and most often will override a second one `onPostExecute(Result)`
    //  Reference: https://developer.android.com/reference/android/os/AsyncTask?authuser=4
    //  Reference: https://stackoverflow.com/a/12447497/6667035
    private class FtpTask extends AsyncTask<Void, Void, FTPClient> {
        //  `doInBackground` invoked on the background thread immediately after `onPreExecute()`
        //  finishes executing. This step is used to perform background computation
        //  that can take a long time. The parameters of the asynchronous task are
        //  passed to this step. The result of the computation must be returned by
        //  this step and will be passed back to the last step. This step can also use
        //  `publishProgress(Progress...)` to publish one or more units of progress.
        //  These values are published on the UI thread, in the `onProgressUpdate(Progress...)`
        //  step.
        protected FTPClient doInBackground(Void... args) {
            FTPconnection ftpConnect = new FTPconnection();
            FTPClient ftp = ftpConnect.connectftp();
            return ftp;
        }

        //  `onPostExecute` invoked on the UI thread after the background computation finishes.
        //  The result of the background computation is passed to this step as
        //  a parameter.
        protected void onPostExecute(FTPClient result) {
            Log.v("FTPTask","FTP connection complete");
            ftpClient = result;
            //Where ftpClient is a instance variable in the main activity
            Log.v("Boolean.toString(ftpClient.isConnected())", Boolean.toString(ftpClient.isConnected()));
            ShowToast(Boolean.toString(ftpClient.isConnected()), Toast.LENGTH_SHORT);
        }
    }
}

Если есть какие-то улучшения, пожалуйста, дайте мне знать.