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;

@Override
protected 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);

}

@Override
public 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(){

@Override
public 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;
}
}