如何在android中设置日期选择器的最小和最大限制？

我正在开发一个应用程序,我正在使用自定义日期和时间选择器.
我已经创建了一个对话框,里面我现在分别@L_489_4@日期和时间选择器,我想设置日期选择器的最小和最大限制.
例如,一个人不应该从今天开始选择前一个日期,也不能超过一个月.
这是我的代码

AlertDialog.builder builder = new AlertDialog.builder(getActivity());
            final DatePicker picker = new DatePicker(getActivity());
            try {
                Field f[] = picker.getClass().getDeclaredFields();
                for (Field field : f) {
                    if (field.getName().equals("mYearPicker") || field.getName().equals("mYearSpinner")) {
                        field.setAccessible(true);
                        Object yearPicker = new Object();
                        yearPicker = field.get(picker);
                        ((View) yearPicker).setVisibility(View.GONE);
                    }
                }
            } catch (Exception eX) {
                ex.printStackTrace();
            }
            picker.setCalendarViewShown(false);
            picker.setMinDate(new  Date().getTime());

            builder.settitle("Please SELEct date on which you would be leaving :")
                    .setView(picker)
                    .setPositiveButton("OK",new DialogInterface.onClickListener() {
                                public void onClick(DialogInterface dialog,int whichButton) {
                                    SimpleDateFormat parseFormat = new SimpleDateFormat("EEE dd MMM");
                                    Date date1 = new Date();
                                    date1.setDate(picker.getDayOfMonth());
                                    date1.setMonth(picker.getMonth());
                                    final String s = parseFormat.format(date1);
                                    Log.e("DATE",s);
                                    SimpleDateFormat sdf=new SimpleDateFormat("MM-dd-yyyy");
                                    Date date2=new Date();
                                    date2.setDate(picker.getDayOfMonth());
                                    date2.setMonth(picker.getMonth());
                                    final String s2=sdf.format(date2);


                                    //Time picker
                                    AlertDialog.builder builder = new AlertDialog.builder(getActivity());
                                    final TimePicker picker = new TimePicker(getActivity());
                                    picker.setIs24HourView(true);
                                    builder.settitle("Please SELEct time at which you would be leaving :")
                                            .setView(picker)
                                            .setPositiveButton("OK",new DialogInterface.onClickListener() {
                                                        public void onClick(DialogInterface dialog,int whichButton) {
                                                            int hour = picker.getCurrentHour();
                                                            int minute = picker.getCurrentminute();
                                                            leaving.setTextSize(14);

                                                            leaving.setText(s + " " + hour + ":" + minutE);
                                                            inTime=s2+" "+hour+":"+minute;
                                                            Log.e("inTime ",inTimE);
                                                        }
                                                    })
                                            .setNegativeButton("Cancel",new DialogInterface.onClickListener() {
                                                public void onClick(DialogInterface dialog,int whichButton) {
                                                    leaving.setText("");
                                                    inTime="";
                                                    dialog.dismiss();
                                                }
                                            }).create().show();
                                    //Time picker
                                }
                            }
                    )
                    .setNegativeButton("Cancel",int whichButton) {
                                    leaving.setText("");
                                    inTime="";
                                    dialog.dismiss();
                                }
                            }
                    )
                    .create().show();

请帮忙.谢谢

public class MainActivity extends Activity {

    TextView txtDatePicker;
    Calendar cal,cal1;
    long maxDate;
    Date date;

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

        cal = Calendar.geTinstance();
        cal1 = Calendar.geTinstance();

        txtDatePicker = (TextView) findViewById(R.id.txtDatePicker);
        txtDatePicker.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                DatePickerDialog dialog = new DatePickerDialog(MainActivity.this,new OnDateSetListener() {

                    @Override
                    public void onDateSet(DatePicker arg0,int arg1,int arg2,int arg3) {
                        // TODO Auto-generated method stub
                        Toast.makeText(MainActivity.this,""+arg1+"/"+(arg2+1)+"/"+arg3,Toast.LENGTH_SHORT).show();
                    }
            },cal.get(Calendar.YEAR),cal.get(Calendar.MONTH),cal.get(Calendar.DAY_OF_MONTH));
            dialog.getDatePicker().setMinDate(System.currentTimeMillis());
            cal1.add(Calendar.YEAR,5);
            dialog.getDatePicker().setMaxDate(cal1.getTimeInMillis());
            dialog.show();
        }
    });
  }
}