刷新后将数据保留在 ListView 中 - Android Studio

Question

我有一个主要活动和 PersonListView 活动。在主活动中，有一些输入文本，当单击保存按钮时，它将发送数据并保存到列表视图。好吧，我在将数据保留在该列表视图中时遇到一些麻烦，因为每次我返回主活动并返回列表视图时，旧数据都会消失。有没有办法保存数据但不使用数据库。

这是我的主要活动：

public class MainActivity extends AppCompatActivity {

    String str, gender, vaccine, date;

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

        Button okay = (Button) findViewById(R.id.btnOk);
        Button list = (Button) findViewById(R.id.btnList);

        EditText name = (EditText) findViewById(R.id.inputName);
        EditText address = (EditText) findViewById(R.id.inputAdd);
        EditText phone = (EditText) findViewById(R.id.inputPhone);

        RadioGroup radioGroup = (RadioGroup) findViewById(R.id.radioGroup);
        RadioButton female = (RadioButton) findViewById(R.id.inputFemale);
        RadioButton male = (RadioButton) findViewById(R.id.inputMale);

        CheckBox first = (CheckBox)findViewById(R.id.inputFirst);
        CheckBox second = (CheckBox)findViewById(R.id.inputSecond);
        CheckBox third = (CheckBox)findViewById(R.id.inputThird);

        EditText datefirst = (EditText) findViewById(R.id.dateFirst);
        EditText datesecond = (EditText) findViewById(R.id.dateSecond);
        EditText datethird = (EditText) findViewById(R.id.dateThird);

        TextView result = (TextView)findViewById(R.id.textResult);


        okay.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(female.isChecked()) gender = female.getText().toString();
                if(male.isChecked()) gender = male.getText().toString();
                if(first.isChecked()) {
                    vaccine = first.getText().toString();
                    date = datefirst.getText().toString();
                }
                if(second.isChecked()) {
                    vaccine = second.getText().toString();
                    date = datesecond.getText().toString();
                }
                if(third.isChecked()) {
                    vaccine = third.getText().toString();
                    date = datethird.getText().toString();
                }

                str = name.getText().toString() + "\n" + address.getText().toString() + "\n" + phone.getText().toString() + "\n" +
                        gender + "\n" + vaccine + "\n" + date;


                result.setText(str);
                Toast.makeText(getApplicationContext(),result.getText().toString(),Toast.LENGTH_SHORT).show();


                Intent intent = new Intent(MainActivity.this, PersonView.class);
                intent.putExtra("NAME",name.getText().toString());
                intent.putExtra("ADDRESS",address.getText().toString());
                intent.putExtra("PHONE",phone.getText().toString());
                intent.putExtra("GENDER",gender);
                intent.putExtra("VACCINE",vaccine);
                intent.putExtra("DATE",date);

                startActivity(intent);

            }
        });

这是 ListView 活动：

public class PersonView extends AppCompatActivity {

ArrayList<Person> listPerson;
PersonListViewAdapter personListViewAdapter;
ListView listViewPerson;

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

    Button back = findViewById(R.id.btnBack);

    back.setOnClickListener(view -> {
        Intent intent = new Intent(PersonView.this, MainActivity.class);
        startActivity(intent);
    });

    listPerson = new ArrayList<>();
    listPerson.add(new Person("Lieu Mai","25 Tran Quang Dieu", "0786367073", "female","3 injection", "24/07/2000"));

    personListViewAdapter = new PersonListViewAdapter(listPerson);
    listViewPerson = findViewById(R.id.listPerson);
    listViewPerson.setAdapter(personListViewAdapter);
    updateList();


}

private void updateList()
{
    Intent intent = getIntent();
    Bundle bundle = intent.getExtras();

    if(bundle != null)
    {
        Person newPerson = new Person((String)bundle.get("NAME"), (String)bundle.get("ADDRESS"), (String)bundle.get("PHONE"), (String)bundle.get("GENDER"),(String)bundle.get("VACCINE"),(String)bundle.get("DATE"));
        listPerson.add(newPerson);
        personListViewAdapter.notifyDataSetChanged();
    }
}


class Person {
    String name, address, phone, gender, vaccine, date;

    public Person( String name, String address, String phone, String gender, String vaccine, String date) {
        this.name = name;
        this.address = address;
        this.phone = phone;
        this.gender = gender;
        this.vaccine = vaccine;
        this.date = date;
    }
}

class PersonListViewAdapter extends BaseAdapter {

    final ArrayList<Person> listPerson;

    PersonListViewAdapter(ArrayList<Person> listPerson) {
        this.listPerson = listPerson;
    }

    @Override
    public int getCount() {

        return listPerson.size();
    }

    @Override
    public Object getItem(int position) {

        return listPerson.get(position);
    }

    @Override
    public long getItemId(int position) {

        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        View viewPerson;
        if (convertView == null) {
            viewPerson = View.inflate(parent.getContext(), R.layout.person_view, null);
        } else viewPerson = convertView;


        Person person = (Person) getItem(position);
        ((TextView) viewPerson.findViewById(R.id.txtName)).setText(String.format("Name: %s", person.name));
        ((TextView) viewPerson.findViewById(R.id.txtAddress)).setText(String.format("Address : %s", person.address));
        ((TextView) viewPerson.findViewById(R.id.txtPhone)).setText(String.format("Phone number: %s", person.phone));
        ((TextView) viewPerson.findViewById(R.id.txtGender)).setText(String.format("Gender: %s", person.gender));
        ((TextView) viewPerson.findViewById(R.id.txtVaccine)).setText(String.format("Vaccine: %s", person.vaccine));
        ((TextView) viewPerson.findViewById(R.id.txtDate)).setText(String.format("Date: %s", person.date));

        return viewPerson;
    }
}
}

Answer 1

您可以将 listPerson 保存在共享首选项中，并在 PersonView Activity 中的 oncreate 方法中检索它。

Answer 2

您可以使用 viewModel 并将其附加到您的 Activity 来保存您的列表，并且该列表将一直处于活动状态，直到您的应用程序实例处于活动状态。
或者，您可以创建一个伴生对象列表，并且伴生对象也会保持活动状态，直到应用程序的实例处于活动状态。

从以上两个选项来看，viewModel 是最好的选择，因为伴随对象会导致内存泄漏问题。

但是，如果您想永久存储数据，则必须使用数据库或sharedPrefences来永久保存您的值。