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;  }}