Question

我只是想从我在网上找到的许多android datepicker教程中创建的一个datepicker对话框中获取日期。一旦选中，我在实际检索文本日期的某个地方似乎出错了。我有一个DatePickerFragment类，它从一个CreateEvent片段调用，该片段嵌套在我的MainActivity活动类中。这是DatePicker：

public class DatePickerFragment extends DialogFragment
        implements DatePickerDialog.OnDateSetListener {

    private EditText txtDate;
    @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);
    }

    public void onDateSet(DatePicker view, int year, int month, int day) {
        txtDate = (EditText)view.findViewById(R.id.txtDate);
        txtDate.setText(day + " " + (month + 1) + " " + year);
    }
}

当我实际尝试设置日期时，我得到Attempt to invoke virtual method 'void android.widget.EditText.setText(java.lang.CharSequence) on a null object reference，我理解这意味着它实际上无法在我的创建事件片段xml文件中找到edittext元素。

我应该如何设置{edit}元素的文本来自onDateSet，还是我必须改变我的方法？

我试了this way，但无济于事。

Answer 1

我是通过以下代码行完成的：

public class DatePickerDialogMy extends DialogFragment {
    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        DateSetting dateSetting=new DateSetting(getActivity());
        Calendar calendar= Calendar.getInstance();
        int year= calendar.get(calendar.YEAR);
        int month=calendar.get(calendar.MONTH);
        int day=calendar.get(calendar.DAY_OF_MONTH);
        DatePickerDialog dialog;
        dialog=new DatePickerDialog(getActivity(),dateSetting,year,month,day);
        return dialog;
    }
}

第二课：

        public class DateSetting implements android.app.DatePickerDialog.OnDateSetListener {
            Context context;
            public DateSetting(Context context){
                this.context=context;

            }
            @Override
            public void onDateSet(DatePicker view, int year, int dateSetting, int dayOfMonth) {
                Toast.makeText(context, "selected date:" + dateSetting + "/" + dayOfMonth + "/" + year, Toast.LENGTH_LONG).show();
        //        MainActivity.test.setText(String.valueOf(dateSetting));
                MyActivity.dobEditText.setText(dateSetting+"/"+dayOfMonth+ "/" + year);
            }
        }

如何致电：

 DatePickerDialogMy datePickerDialog = new DatePickerDialogMy();
                datePickerDialog.show(getSupportFragmentManager(), "date_picker");

Answer 2

您需要使用界面来获取datepicker到来电者fragment的数据：

public interface DateListener {
    void passDate(String date);
}

创建名为mListener的成员变量：

private DateListener mListener;

覆盖onAttach＆amp; onDetach fragment方法：

@Override
public void onAttach(Activity activity) {
    super.onAttach(activity);
    try {
        mListener = (DateListener) activity;
    } catch (ClassCastException e) {
        throw new ClassCastException(activity.toString() + " must implement DateListener");
    }
}

@Override
public void onDetach() {
    super.onDetach();
    mListener = null;
}

接下来，在来电者interface中实施此fragment并覆盖passDate方法：

@Override
public void passDate(String date) {
    // Do something with 'date', yourEditText.setText(date) for the example
}

你应该好好去。

尝试从DatePicker DialogFragment设置EditText的文本

2 个答案: