android之datepicker控件的用法

<?xml version="1.0" encoding="utf-8"?>
<linearlayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  >
<textview 
  android:id="@+id/textviewdatedisplay" 
  android:layout_width="wrap_content" 
  android:layout_height="wrap_content" 
  />
<button 
  android:id="@+id/btnpickdate"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:text="change the date"
  />
</linearlayout>

package com.example.mars_2200_datepicker;

import java.util.calendar;

import android.support.v7.app.actionbaractivity;
import android.support.v7.app.actionbar;
import android.support.v4.app.fragment;
import android.app.datepickerdialog;
import android.app.dialog;
import android.os.bundle;
import android.view.layoutinflater;
import android.view.menu;
import android.view.menuitem;
import android.view.view;
import android.view.viewgroup;
import android.widget.button;
import android.widget.datepicker;
import android.widget.textview;
import android.os.build;

public class mainactivity extends actionbaractivity {
  private textview textviewdatedisplay;
  private button btnpickdate;
  private int myear;
  private int mmonth;
  private int mday;

  static final int date_dialog_id = 0;

  @override
  protected void oncreate(bundle savedinstancestate) {
    super.oncreate(savedinstancestate);
    setcontentview(r.layout.activity_main);

    textviewdatedisplay = (textview) findviewbyid(r.id.textviewdatedisplay);
    btnpickdate = (button) findviewbyid(r.id.btnpickdate);

    btnpickdate.setonclicklistener(new view.onclicklistener() {
      public void onclick(view v) {
        showdialog(date_dialog_id);
      }
    });
    final calendar c = calendar.getinstance();
    myear = c.get(calendar.year);
    mmonth = c.get(calendar.month);
    mday = c.get(calendar.day_of_month);

    updatedisplay();
  }

  @override
  public boolean oncreateoptionsmenu(menu menu) {

    // inflate the menu; this adds items to the action bar if it is present.
    getmenuinflater().inflate(r.menu.main, menu);
    return true;
  }

  @override
  public boolean onoptionsitemselected(menuitem item) {
    // handle action bar item clicks here. the action bar will
    // automatically handle clicks on the home/up button, so long
    // as you specify a parent activity in androidmanifest.xml.
    int id = item.getitemid();
    if (id == r.id.action_settings) {
      return true;
    }
    return super.onoptionsitemselected(item);
  }

  /**
   * a placeholder fragment containing a simple view.
   */
  public static class placeholderfragment extends fragment {

    public placeholderfragment() {
    }

    @override
    public view oncreateview(layoutinflater inflater, viewgroup container,
        bundle savedinstancestate) {
      view rootview = inflater.inflate(r.layout.fragment_main, container,
          false);
      return rootview;
    }
  }

  private void updatedisplay() {
    textviewdatedisplay.settext(new stringbuilder().append(myear).append("-")
        .append(mmonth + 1).append("-").append(mday).append(" "));
  }

  private datepickerdialog.ondatesetlistener mdatesetlistener = new datepickerdialog.ondatesetlistener() {
    public void ondateset(datepicker view, int year, int monthofyear,
        int dayofmonth) {
      myear = year;
      mmonth = monthofyear;
      mday = dayofmonth;
      updatedisplay();
    }
  };

  protected dialog oncreatedialog(int id) {
    switch (id) {
    case date_dialog_id:
      return new datepickerdialog(this, mdatesetlistener, myear, mmonth,
          mday);
    }
    return null;
  }
}