如何从我的 DatePicker 片段中传输格式化的日期字符串？

Posted 2023-04-19

【中文标题】如何从我的 DatePicker 片段中传输格式化的日期字符串？

【英文标题】：How to transfer the formatted date string from my DatePickerFragment?

【发布时间】：2013-08-15 05:19:56

【问题描述】：

关注官方文档http://developer.android.com/guide/topics/ui/controls/pickers.html#DatePicker。

我只使用了相同的代码，并且只在onDateSet 方法中添加了结果格式：

public 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);
    

    @Override
    public void onDateSet(DatePicker view, int year, int month, int day) 
        Calendar c = Calendar.getInstance();
        c.set(year, month, day);

        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        String formattedDate = sdf.format(c.getTime());

        // How to get the string from here to the caller?

    

为了测试，调用者活动只显示TextView，并在用户触摸小部件时调用选择器：

public class OrderHeadEditActivity extends Activity 

    private TextView mDTDelivery;
    ...

    @Override
    protected void onCreate(Bundle bundle) 
        ...
        mDTDelivery = (TextView) findViewById(R.id.order_head_view_dt_delivery);
        ...
        mDTDelivery.setOnClickListener(new View.OnClickListener() 
            @Override
            public void onClick(View v) 
                DialogFragment picker = new DatePickerFragment();
                picker.show(getFragmentManager(), "datePicker");
            
        );
    
...

显示日期选择器，在结果格式化为字符串的地方设置断点后，我可以看到它起作用了。

但是，我不知道如何将字符串值传回mtDTDelivery 小部件？

【问题讨论】：

让你的数据选择器类成为你的活动类的内部类

您尝试过以下方法吗？？接口方法将起作用。

我还没试过。我会在今天晚些时候尝试。我想先了解一下。 （我是 Java 及其 iterfaces 的新手，也是 Android 的新手。）

【参考方案1】：

正如 tyczj 指出的那样，您可以使用接口方法，或者您可以将 datapicker 类设为活动类的内部类，在这种情况下，它应该是静态的，并且您需要外部类的弱引用

使用界面。

在DatePickerFragment 中定义一个接口。在您的活动类中实现接口并将日期设置为 textview。

public class DatePickerFragment extends DialogFragment
implements DatePickerDialog.OnDateSetListener 

    TheListener listener;

public interface TheListener
    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 = (TheListener) getActivity(); 

// 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) 
Calendar c = Calendar.getInstance();
c.set(year, month, day);

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
String formattedDate = sdf.format(c.getTime());
if (listener != null) 

  listener.returnDate(formattedDate); 

主活动

public class MainActivity extends Activity implements DatePickerFragment.TheListener

    Button b;
    TextView tv;
    @Override
    protected void onCreate(Bundle savedInstanceState) 
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        b= (Button) findViewById(R.id.button1);
        tv= (TextView) findViewById(R.id.textView1);
        b.setOnClickListener(new OnClickListener()
        

            @Override
            public void onClick(View arg0) 
                // TODO Auto-generated method stub
                DialogFragment picker = new DatePickerFragment();
                picker.show(getFragmentManager(), "datePicker");
            

        );
    

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

    @Override
    public void returnDate(String date) 
        // TODO Auto-generated method stub
        tv.setText(date);
    

第二种方法不确定这是否是最好的方法。我会推荐上面的接口方法。

public class MainActivity extends Activity //implements DatePickerFragment.TheListener

    Button b;
    TextView tv;
    @Override
    protected void onCreate(Bundle savedInstanceState) 
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        b= (Button) findViewById(R.id.button1);
        tv= (TextView) findViewById(R.id.textView1);
        b.setOnClickListener(new OnClickListener()
        

            @Override
            public void onClick(View arg0) 
                // TODO Auto-generated method stub
                DialogFragment picker = new DatePickerFragment();
                picker.show(getFragmentManager(), "datePicker");
            

        );
    

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


    public static class DatePickerFragment extends DialogFragment
    implements DatePickerDialog.OnDateSetListener 

        private WeakReference<MainActivity> mActivity;

    @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);
    mActivity = new WeakReference<MainActivity>((MainActivity) getActivity());

    // 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) 
    Calendar c = Calendar.getInstance();
    c.set(year, month, day);

    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
    String formattedDate = sdf.format(c.getTime());
      MainActivity target = mActivity.get(); 
      if (target != null) target.tv.setText(formattedDate);

    
    

【讨论】：

我得再研究一下。无论如何，DatePickerFragment 中的listener 是如何获得其非空值的？

你在DatePickerFragment中定义了一个接口。然后在您的活动类中实现接口。您将值设置为接口方法。由于您的活动类实现了接口，因此您在那里获得了价值。检查主题为活动创建事件回调 developer.android.com/guide/components/…

@pepr 了解接口。 docs.oracle.com/javase/tutorial/java/concepts/interface.html

谢谢，它有效。我之前没有注意到listener = (TheListener) getActivity(); :) 也感谢您的链接。

@Raghunandan 当我添加此行 listener = (TheListener) getActivity(); 并单击 EditTextBox 时，应用程序停止工作并自动关闭

【参考方案2】：

正确的方法是为传递字符串的活动创建回调。

看看Communicating with an Activity