在android studio中获取datepicker（年，月，日）日期的按钮

Question

我想从android studio中的日期选择器中获取看起来像那个（“Year-mm-DD”）的日期，并在按下按钮时将其与当前日期进行比较。

public class UserMenu extends ActionBarActivity {
    DatePicker date;
    ImageButton next;
    Date currentDate;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.user_menu);
        date = (DatePicker) findViewById(R.id.datePicker);
        next = (ImageButton) findViewById(R.id.nxt);
        currentDate = new Date();
        next.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                SimpleDateFormat dateformat = new SimpleDateFormat("yyyy-MM-dd");
                String dateFormat = dateformat.format(new Date(date.getYear(), date.getMonth(), date.getDayOfMonth()));
                String nowDate = new SimpleDateFormat("yyyy-MM-dd").format(currentDate);
                if (dateFormat.compareTo(nowDate) < 0) {
                    Toast.makeText(getApplicationContext(), "The date is too old", Toast.LENGTH_LONG);
                } else {
                    Intent i = new Intent(UserMenu.this, UserMenuTime.class);
                    i.putExtra("date", dateFormat);
                    startActivity(i);
                }
            }
        });
    }
}

Answer 1

使用before和after方法比较日期：

   Date pickerDate = new Date(date.getYear(), date.getMonth(), date.getDayOfMonth());
   if (pickerDate.before(currentDate)) {
       Toast.makeText(getApplicationContext(), "The date is too old", Toast.LENGTH_LONG);
   } else {
       Intent i = new Intent(UserMenu.this, UserMenuTime.class);
       i.putExtra("date", dateFormat);
       startActivity(i);
   }