DataPickerDialog

.xml

    <Button
        android:text="날짜 선택"
        android:id="@+id/buttonDate"

.java

        Calendar calendar = Calendar.getInstance();
        int year = calendar.get(Calendar.YEAR);
        int month = calendar.get(Calendar.MONTH);
        int day = calendar.get(Calendar.DAY_OF_MONTH);
        final DatePickerDialog dateDialog =
                new DatePickerDialog(this, new DatePickerDialog.OnDateSetListener() {
            @Override
            public void onDateSet(DatePicker view, int year, int monthOfYear, int dayOfMonth) {
                String msg = String.format("%d/%d/%d", year, monthOfYear + 1, dayOfMonth);
                Toast.makeText(MainActivity.this, msg, Toast.LENGTH_SHORT).show();
            }
        }, year, month, day);

        Button buttonDate = (Button)findViewById(R.id.buttonDate);
        buttonDate.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                dateDialog.show();
            }
        });