如何从我的 DatePicker 片段中传输格式化的日期字符串？

Question

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？

Answer 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);

    }
    }
}

Answer 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