帮我生成一个Android日期多选的代码

以下是一个简单的 Android 日期多选的示例代码，使用了 DatePickerDialog 和 Calendar 对象实现：

public class MainActivity extends AppCompatActivity {

    private TextView selectedDatesTextView;
    private Button pickDatesButton;

    private Calendar calendar;
    private int year, month, day;
    private HashSet<String> selectedDates;

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

        selectedDatesTextView = findViewById(R.id.selected_dates_text_view);
        pickDatesButton = findViewById(R.id.pick_dates_button);

        selectedDates = new HashSet<>();

        pickDatesButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                calendar = Calendar.getInstance();
                year = calendar.get(Calendar.YEAR);
                month = calendar.get(Calendar.MONTH);
                day = calendar.get(Calendar.DAY_OF_MONTH);

                DatePickerDialog datePickerDialog = new DatePickerDialog(MainActivity.this,
                        R.style.DatePickerTheme,
                        new DatePickerDialog.OnDateSetListener() {
                            @Override
                            public void onDateSet(DatePicker datePicker, int selectedYear, int selectedMonth, int selectedDay) {
                                calendar.set(selectedYear, selectedMonth, selectedDay);
                                SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
                                String selectedDate = sdf.format(calendar.getTime());
                                if (selectedDates.contains(selectedDate)) {
                                    selectedDates.remove(selectedDate);
                                } else {
                                    selectedDates.add(selectedDate);
                                }
                                updateSelectedDatesTextView();
                            }
                        }, year, month, day);
                datePickerDialog.getDatePicker().setCalendarViewShown(false);
                datePickerDialog.setCancelable(false);
                datePickerDialog.show();
            }
        });
    }

    private void updateSelectedDatesTextView() {
        if (selectedDates.isEmpty()) {
            selectedDatesTextView.setText("No dates selected.");
        } else {
            StringBuilder stringBuilder = new StringBuilder();
            for (String date : selectedDates) {
                stringBuilder.append(date).append("\n");
            }
            selectedDatesTextView.setText(stringBuilder.toString());
        }
    }
}

在布局文件中，可以添加一个 TextView 和一个 Button：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:id="@+id/pick_dates_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Pick Dates"
        android:layout_centerInParent="true"/>

    <TextView
        android:id="@+id/selected_dates_text_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="18sp"
        android:textStyle="bold"
        android:layout_below="@+id/pick_dates_button"
        android:layout_marginTop="16dp"
        android:layout_centerHorizontal="true"/>
</RelativeLayout>

这份代码会在用户点击按钮时弹出一个日期选择器，用户可以选择多个日期，选择的日期会显示在 TextView 中。你可以根据需要进行修改和优化。