How to create a date and time picker in Android?

Use this function it will enable you to pic date and time one by one then set it to global variable date. No library no XML.

Calendar date;
public void showDateTimePicker() {
   final Calendar currentDate = Calendar.getInstance();
   date = Calendar.getInstance();
   new DatePickerDialog(context, new DatePickerDialog.OnDateSetListener() {
       @Override
       public void onDateSet(DatePicker view, int year, int monthOfYear, int dayOfMonth) {
            date.set(year, monthOfYear, dayOfMonth);
            new TimePickerDialog(context, new TimePickerDialog.OnTimeSetListener() {
                @Override
                public void onTimeSet(TimePicker view, int hourOfDay, int minute) {
                    date.set(Calendar.HOUR_OF_DAY, hourOfDay);
                    date.set(Calendar.MINUTE, minute);
                    Log.v(TAG, "The choosen one " + date.getTime());
                }
            }, currentDate.get(Calendar.HOUR_OF_DAY), currentDate.get(Calendar.MINUTE), false).show();
       }
   }, currentDate.get(Calendar.YEAR), currentDate.get(Calendar.MONTH), currentDate.get(Calendar.DATE)).show();
}

Put both DatePicker and TimePicker in a layout XML.

date_time_picker.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:padding="8dp"
    android:layout_height="match_parent">

    <DatePicker
        android:id="@+id/date_picker"
        android:layout_width="match_parent"
        android:calendarViewShown="true"
        android:spinnersShown="false"
        android:layout_weight="4"
        android:layout_height="0dp" />

    <TimePicker
        android:id="@+id/time_picker"
        android:layout_weight="4"
        android:layout_width="match_parent"
        android:layout_height="0dp" />

    <Button
        android:id="@+id/date_time_set"
        android:layout_weight="1"
        android:layout_width="match_parent"
        android:text="Set"
        android:layout_height="0dp" />

</LinearLayout>

The code:

final View dialogView = View.inflate(activity, R.layout.date_time_picker, null);
final AlertDialog alertDialog = new AlertDialog.Builder(activity).create();

dialogView.findViewById(R.id.date_time_set).setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {

         DatePicker datePicker = (DatePicker) dialogView.findViewById(R.id.date_picker);
         TimePicker timePicker = (TimePicker) dialogView.findViewById(R.id.time_picker);

         Calendar calendar = new GregorianCalendar(datePicker.getYear(),
                            datePicker.getMonth(),
                            datePicker.getDayOfMonth(),
                            timePicker.getCurrentHour(),
                            timePicker.getCurrentMinute());

         time = calendar.getTimeInMillis();
         alertDialog.dismiss();
    }});
alertDialog.setView(dialogView);
alertDialog.show();