android datepickerfragment 将信息传递给主要 Activity

Question

我是编程和 Android 方面的新手。我在使用 datePickerfragment 时遇到问题。在 mainActivity 上实现 DatePickerFragment.OnFragmentInteractionListener 时出错，它说“MainActivity 类必须声明为抽象或在‘OnFragmentInteractionListener’中实现抽象方法‘returnDate(String)’。”

我使用了 datePicker，如 http://developer.android.com/guide/topics/ui/controls/pickers.html 所示.

datePicker 可以工作，但我想将选择的值传输到 mainActivity，我在另一篇文章中得到了一些提示:How to transfer the formatted date string from my DatePickerFragment? .

我真的不知道我错过了什么。我还想知道是否可以传输日期值而不是字符串值。我想在 mainActivity 中操作日期。希望可以有人帮帮我。这是我的代码:

package com.example.android.datepickertest;

import android.app.Activity;
import android.os.Bundle;
import android.support.v4.app.DialogFragment;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.TextView;

public class MainActivity extends FragmentActivity
        implements DatePickerFragment.OnFragmentInteractionListener
        {
 private TextView dataSelecionada;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        dataSelecionada = (TextView)findViewById(R.id.data_selecionada);
    }

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

    }

@Override
    public void setTextDate (int year, int month, int day) {
        TextView displayDataSelecionada = (TextView) findViewById(R.id.data_selecionada);
        dataSelecionada.setText(day + "/" + month +"/" + year);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

---

和datePickerFragment:n

package com.example.android.datepickertest;

import android.app.Activity;
import android.app.DatePickerDialog;
import android.app.Dialog;
import android.app.Fragment;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.DialogFragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.DatePicker;
import android.widget.TextView;

import java.text.SimpleDateFormat;
import java.util.Calendar;


/**
 * A simple {@link Fragment} subclass.
 * Activities that contain this fragment must implement the
 * {@link DatePickerFragment.OnFragmentInteractionListener} interface
 * to handle interaction events.
 * Use the {@link DatePickerFragment#newInstance} factory method to
 * create an instance of this fragment.
 */
public class DatePickerFragment extends DialogFragment
        implements DatePickerDialog.OnDateSetListener {

    OnFragmentInteractionListener listener;

    public interface OnFragmentInteractionListener {
        public void returnDate(String date);

    };

    @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);
        listener=(OnFragmentInteractionListener)getActivity();

        // 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) {
        // Do something with the date chosen by the user
        Calendar c= Calendar.getInstance();
        c.set(year,month,day);
        SimpleDateFormat date = new SimpleDateFormat();
        String dateSet = date.format(c.getTime());
        if (listener !=null){
            listener.returnDate(dateSet);
        }

    }
}

Answer 1

错误有答案，当你实现一个接口(interface)时，你应该实现接口(interface)中的所有方法。

在您的情况下，您的 mainactivity 中没有方法 returndate。

1.创建方法 returnDate 或者如果您使用 Android studio，只需转到文件 MainActivity 并将光标放在“public class MainActivity”上，然后按 Alt+Enter，系统将自动创建该方法，您将在其中输入日期你的主要 Activity 通过这个方法。

1. 如果您需要日期而不是字符串，请将 returndate 方法的参数更改为 Date，并删除 Simpledateformat 而是使用

新日期(c.getTime())