android 的DatePicker怎么取出 年月日的值

private TextView t;//定义一个textview控件
private DatePicker dp;//日期控件
dp=(DatePicker)findViewById(R.id.datePicker1);取得id
t=(TextView)findViewById(R.id.text)取得id
dp.init(ca.get(Calendar.YEAR),ca.get(Calendar.MONTH),
ca.get(Calendar.DAY_OF_MONTH),
new DatePicker.OnDateChangedListener() {
//监听选择的出生日期
@Override
public void onDateChanged(DatePicker view, int year, int monthOfYear,
int dayOfMonth) {
// TODO Auto-generated method stub
ca.set(year, monthOfYear,dayOfMonth);//改变日期

t.setText(year+"年"+monthOfYear+"月"+dayOfMonth+"日");
//取得值
}
});