Android：ListView 位置和 DatePicker

Question

我有 onItemClickListener 用于在单击项目时打开 DatePicker 对话框的 ListView：

list.setOnItemClickListener(new AdapterView.OnItemClickListener() {
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        showDatePickerDialog(view);
    }
});

public void showDatePickerDialog(View v) {
    DialogFragment newFragment = new DatePickerFragment();
    newFragment.show(getFragmentManager(), "datePicker");
}

在 DatePicker 中设置日期后，我有 onDateSet 方法，我想用它来更新数据库并为在 ListView 中单击的项目设置日期：

public void onDateSet(DatePicker view, int year, int month, int day) {
    ...
    dataSource.updateDate(adapter.getItemId(position), month + "/" + day + "/" + year);
    ...
} 

如何将被点击项目的 ListView 位置传递给 onDateSet，以便我的数据库助手知道要更新哪条记录？

---

编辑：这是 DatePickerFragment 类：

public static class DatePickerFragment extends DialogFragment
        implements DatePickerDialog.OnDateSetListener {

    @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) {
        ...
        dataSource.updateDate(adapter.getItemId(position), month + "/" + day + "/" + year);
        ...
    }
}

谢谢！

Answer 1

将position 发送到DatePickerFragment - 我想这是您自己的课程。通过参数发送此参数（因为这是在片段重新创建中保护代码的最佳实践）：

public class DatePickerFragment extends Fragment {

    private DatePickerListener datePickerListener;
    private int listPosition = -1;
    private static final String POSITION_ARG_KEY = "POSITION_ARG_KEY";

    public static DatePickerFragment newInstance(int position) {
        DatePickerFragment fragment = new DatePickerFragment();
        Bundle args = new Bundle();
        args.putInt(POSITION_ARG_KEY, position);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Bundle args = getArguments();
        if (args != null) {
            listPosition = args.getInt(POSITION_ARG_KEY);
        }
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        if (activity instanceof DatePickerListener) {
            datePickerListener = (DatePickerListener) activity;
        }
    }

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

    public void methodThatCallsActivity() {
        if(datePickerListener) {
            datePickerListener.onDateSet(datePicker, year, month, day, this.listPosition);
        }
    }

    // / the rest of the code

    public static interface DatePickerListener {
        public void onDateSet(DatePicker view, int year, int month, int day, int listPosition);
    }
}

然后在显示fragment的activity中，（必须实现DatePickerListener）：

A.发送列表位置：

public void showDatePickerDialog(int listPosition) {
    DialogFragment newFragment = DatePickerFragment.newInstance(listPosition);
    newFragment.show(getFragmentManager(), "datePicker");
}

B.从列表项单击调用此方法：

list.setOnItemClickListener(new AdapterView.OnItemClickListener() {
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        showDatePickerDialog(position);
    }
});

C.您在onDateSet 实现中的列表位置：

public void onDateSet(DatePicker view, int year, int month, int day, int listPosition) {
    // your relevant code
}

简述：通过参数和参数将列表位置从列表视图发送到片段，然后从那里发送到父活动。

Answer 2

通过以下方式解决：

使DatePickerFragment 成为自己的类（不嵌套在MainActivity 类中）：

public class DatePickerFragment extends DialogFragment {
    @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(), (MainActivity)getActivity(), year, month, day);
    }
}

---

这就是我的MainActivity 班级最终的样子：

public class MainActivity extends ListActivity implements DatePickerDialog.OnDateSetListener {
    private long listId = -1;
    private int listPosition = -1;
    private String date;
    ...

    protected void onCreate(Bundle savedInstanceState) {
        list.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                listId = id;
                listPosition = position;
                showDatePickerDialog(view);
    ...

    // Show DatePicker when clicking on contact in ListView
    public void showDatePickerDialog(View view) {
        DialogFragment newFragment = new DatePickerFragment();
        newFragment.show(getFragmentManager(), "datePicker");
    }

    // Update database and ListView adapter with selected date
    public void onDateSet(DatePicker view, int year, int month, int day) {
        date = (month + 1) + " " + day + ", " + year;
        ...
        dataSource.updateDate(listId, date);
        adapter.setDate(listPosition, date);
        ...
        adapter.notifyDataSetChanged();
        dataSource.close();
    }

---

旁注：按下 DatePicker 的取消按钮（和 Android 后退按钮）仍会将默认日期保存到数据库并更新适配器。这是解决此问题的帖子：https://stackoverflow.com/a/15289569/1261256