Android：日期选择器对话框片段：垃圾回收的大量呼吁

这是我的小程序，用于测试日期选择器对话框。

MainActivity.java

public class MainActivity extends FragmentActivity implements OnClickListener {

Button bSelectDate;



@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    bSelectDate = (Button) findViewById(R.id.bSelectDate);
    bSelectDate.setOnClickListener(this);

}

@Override
public void onClick(View v) {
    // TODO Auto-generated method stub
    DateDialogFragment date = new DateDialogFragment();
    date.setCallBack(onDate);
    date.show(getSupportFragmentManager(), "Date Picker");

}

OnDateSetListener onDate = new OnDateSetListener() {

    @Override
    public void onDateSet(DatePicker view, int year, int monthOfYear,int dayOfMonth) {
        Calendar cal = Calendar.getInstance();
        cal.set(Calendar.YEAR, year);
        cal.set(Calendar.MONTH, monthOfYear);
        cal.set(Calendar.DAY_OF_MONTH, dayOfMonth);



        Toast.makeText(MainActivity.this, ""+String.valueOf(cal.getTimeInMillis()), Toast.LENGTH_LONG).show();

    }
};

}

DateDialogFragment.java

public class DateDialogFragment extends DialogFragment{

Calendar cal;
OnDateSetListener onDateSet;
private int year,month,day;

public void setCallBack(OnDateSetListener onDateSet)
{
    this.onDateSet = onDateSet;
}


@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    Calendar cal = Calendar.getInstance();
    year=cal.get(Calendar.YEAR);
    month=cal.get(Calendar.MONTH);
    day=cal.get(Calendar.DAY_OF_MONTH);


    return new DatePickerDialog(getActivity(), onDateSet, year, month, day);
}

}

程序正常运行，但是问题是，一旦按下按钮，LogCat就会报告许多垃圾回收的调用，例如已释放的GC_CONCURRENT，已释放的GC_FOR_ALLOC，GREF已增加到201。等等。这引起了我的注意，是否存在我可以用这个小程序减少垃圾收集的数量。