在Android中从DatePickerFragment获取Date对象

Question

我已经在我的android应用程序中定义了DatePickerFragment，下面是它的代码：

public class DatePickerFragment extends DialogFragment implements
        DatePickerDialog.OnDateSetListener {

    private int year;
    private int month;
    private int day;


    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        // Use the current date as the default date in the picker
        final Calendar c = Calendar.getInstance();
        int year = c.get(Calendar.YEAR);
        int month = c.get(Calendar.MONTH);
        int day = c.get(Calendar.DAY_OF_MONTH);

        // Create a new instance of DatePickerDialog and return it
        return new DatePickerDialog(getActivity(), this, year, month, day);

    }

    @Override
    public void onDateSet(DatePicker view, int year, int month, int day) {
        this.year = year;
        this.month = month;
        this.day = day;
    }

    public Date getDateFromDatePicker(){
        Calendar calendar = Calendar.getInstance();
        calendar.set(year, month, day);
        return calendar.getTime();
    }
}

我想从TaskFragment中从这个日期选取器中检索日期，并将我的类任务中的“date”属性设置为等于选定的日期

        // Method for date picker to appear once the "Due Date" button is clicked.
    datePickerButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            FragmentManager fm = getActivity().getFragmentManager();
            DatePickerFragment datePicker = new DatePickerFragment();
            datePicker.show(fm, "datePicker");

            task.setDate(datePicker.getDateFromDatePicker());
           //test
           System.out.println(task.getDate());


        }
    });

单击该按钮时将显示日期选择器。但是，日期设置不正确，实际上是在按下日期按钮时设置的，而不是在从选择器中选择日期时设置的。此外，在打印日期时，无论选择什么日期，我都会得到以下结果：I/system.out：Wed Dec 31 10:47:38 GMT+00:002阅读这里的一些解决方案指示我定义onDateSet和getDateFromDatePicker方法，但它们似乎不能正常工作。非常感谢任何帮助，谢谢！

Answer 1

经过一番挖掘，我遵循了我在《Android Programming：the Big Nerd Ranch Guide》一书中读到的方法，该方法明确规定了如何在两个片段之间传递数据。下面是我遵循的步骤：

1. 设置目标片段：在这里，我通过setTargetFragment方法将接收日期的片段（在我的示例中为TaskFragment）设置为DatePickerFragment的目标片段

    // set taskFragment as the target fragment of DatePickerFragment
    datePicker.setTargetFragment(TaskFragment.this, 0);
    datePicker.show(fm, "datePicker");

    public void onDateSet(DatePicker view, int year, int month, int day) {
        // create date object using date set by user
        Calendar calendar = Calendar.getInstance();
        calendar.set(year, month, day);
        Date date = calendar.getTime();

        if (getTargetFragment() == null)
            return;

        Intent intent = new Intent();
        intent.putExtra(DATE, date);

        // pass intent to target fragment
        getTargetFragment().onActivityResult(getTargetRequestCode(), Activity.RESULT_OK, intent);

    @Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (resultCode != Activity.RESULT_OK){
            return;
        }

        if (requestCode == REQUEST_DATE){
            Date date = (Date) data.getSerializableExtra(DatePickerFragment.DATE);
            task.setDate(date);

        }
    }