Как получить общий список предпочтений arraylist - Android Studio

Question

Я пытаюсь сохранить собственный список IP-адресов в SharedPreferences.Я думаю, что это работает, но я изо всех сил пытаюсь показать этого arraylist.Я использую два класса для общих настроек: saveData и loadData.Проблема в том, что при загрузке данных в этом классе должно быть что-то не так.Я приложил свой полный код ниже.Я так старался, чтобы это заработало, пожалуйста, помогите.

private TextView mTextMessage;

private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
        = new BottomNavigationView.OnNavigationItemSelectedListener() {

    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
        switch (item.getItemId()) {
            case R.id.navigation_home:
                mTextMessage.setText(R.string.title_home);

                Intent intent = new Intent(Homepage.this, Login.class);
                startActivity(intent);

                return true;
            case R.id.navigation_dashboard:
                mTextMessage.setText(R.string.title_dashboard);
                return true;
            case R.id.navigation_notifications:
                mTextMessage.setText(R.string.title_notifications);
                return true;
        }
        return false;
    }
};

private Button btnScan;
private ListView listViewIp;
ArrayList<String> ipList;
ArrayAdapter<String> adapter;



getSharedPreferences("USER",MODE_PRIVATE);


@Override
protected void onCreate(Bundle savedInstanceState) {
    loadData();
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_homepage);

    BottomNavigationView navigation = (BottomNavigationView) findViewById(R.id.navigation);
    navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);

    Button buttonSave = findViewById(R.id.button_save);
    buttonSave.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            saveData();
        }
    });

    btnScan = (Button)findViewById(R.id.scan);
    listViewIp = (ListView)findViewById(R.id.listviewip);


    ipList = new ArrayList<>();
    adapter = new ArrayAdapter<String>(this,
            android.R.layout.simple_list_item_1, android.R.id.text1, ipList);
    listViewIp.setAdapter(adapter);


//    loadData();


    btnScan.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            new ScanIpTask().execute();

            listViewIp.setOnItemClickListener(new OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                    switch (position){
                        case 0:
                            Intent intent = new Intent(Homepage.this, Details.class);
                            startActivity(intent);
                            break;
                        case 1:
                           // ipList.remove(1);
                          //  Intent banaan = new Intent(Homepage.this, Register.class);
                          //  startActivity(banaan);
                            Toast.makeText(getApplicationContext(), "Banan" + ipList.size(), Toast.LENGTH_SHORT).show();
                        case 3:
                            loadData();
                            break;

                    }


                }
            });
        }


    });}

String ip = "";
String subnet = "10.0.2.";

private String getSubnetAddress(int address)
{
    String ipString = String.format(
            "%d.%d.%d",
            (address & 0xff),
            (address >> 8 & 0xff),
            (address >> 16 & 0xff));

    return ipString;
}


public void saveData(){
    SharedPreferences sharedpreferences = getSharedPreferences("Shared Preferences", MODE_PRIVATE);
    SharedPreferences.Editor editor =sharedpreferences.edit();
    Gson gson = new Gson();
     String json = gson.toJson(ipList);
    editor.putString("task list", json);
    editor.apply();
    Toast.makeText(Homepage.this, json,  Toast.LENGTH_LONG).show();

}


private void loadData(){

    Toast.makeText(Homepage.this, "Banaan...", Toast.LENGTH_LONG).show();
    SharedPreferences sharedpreferences = getSharedPreferences("Shared Preferences", MODE_PRIVATE);
    Gson gson = new Gson();
    String json = sharedpreferences.getString("task list", null);
    Type type = new TypeToken<ArrayList<String>>(){}.getType();

    ipList = gson.fromJson(json, type);
    if(ipList == null){
        ipList = new ArrayList<>();

    }
}



class ScanIpTask extends AsyncTask<Void, String, Void>{
    /*
    Scan IP 192.168.1.100~192.168.1.110
    you should try different timeout for your network/devices
     */
    // static final String subnet = "10.0.2.";
    static final int lower = 0;
    static final int upper = 254;
    static final int timeout = 50;

    @Override
    protected void onPreExecute() {
        ipList.clear();
        adapter.notifyDataSetInvalidated();
        Toast.makeText(Homepage.this, "Scan IP...", Toast.LENGTH_LONG).show();
    }

    @Override
    protected Void doInBackground(Void... params) {

        for (int i = lower; i <= upper; i++) {
            String host = subnet + i;

            try {
                InetAddress inetAddress = InetAddress.getByName(host);
                if (inetAddress.isReachable(timeout)){
                    publishProgress(inetAddress.toString().split("/")[1]);
                }

            } catch (UnknownHostException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        return null;
    }


    @Override
    protected void onProgressUpdate(String... values) {
        ipList.add(values[0]);
        adapter.notifyDataSetInvalidated();
        Toast.makeText(Homepage.this, values[0], Toast.LENGTH_LONG).show();
    }

    @Override
    protected void onPostExecute(Void aVoid) {
        Toast.makeText(Homepage.this, "Done", Toast.LENGTH_LONG).show();
    }
}