DatePickerDialog的应用中的使用

public class MainActivity extends Activity implements OnClickListener {private Button btn;private TextView tv;Calendar calendar =Calendar.getInstance(Locale.CHINA);//全局使用的calendar final int DATE = 1;  @Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);btn=(Button)this.findViewById(R.id.button1);tv=(TextView)this.findViewById(R.id.tv);btn.setOnClickListener(this);}@Overridepublic void onClick(View v) {switch(v.getId()){case R.id.button1:new DatePickerDialog(MainActivity.this,listener,calendar.get(Calendar.YEAR),calendar.get(Calendar.MONTH),calendar.get(Calendar.DAY_OF_MONTH )).show();}}private DatePickerDialog.OnDateSetListener listener=new DatePickerDialog.OnDateSetListener(){@Overridepublic void onDateSet(DatePicker view, int year, int monthOfYear,int dayOfMonth) {calendar.set(Calendar. YEAR , year);//重置年份calendar.set(Calendar. MONTH , monthOfYear);//重置月份  calendar.set(Calendar. DAY_OF_MONTH , dayOfMonth);//重置日期  update(DATE);//调用更新日期显示  }};private void update(int dt){switch (dt) {case DATE:SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");tv.setText(simpleDateFormat.format(calendar.getTime()));break;default:break;}}