日期选择器对话框中的日期未在弹出 android 的文本视图中设置

Question

我的问题是 onDateSet 方法，我如何从我的 textview 字段上的 datepicker 对话框中检索选定的日期，这是一个嵌入在弹出窗口中的活动。我得到空指针异常： ((TextView) getActivity().findViewById(R.id.spinner_date)).setText("Date"+year);

DatePickerFragment.java

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);
}


public void onDateSet(DatePicker view, int year, int month, int day) {
     Log.w("DatePicker", "Date = " + year);
  ((TextView) getActivity().findViewById(R.id.spinner_date)).setText("Date"+year);
}

}

在 MainActivity.java 中

     public void createVideoEvent(View arg0) {
    LayoutInflater layoutInflater
            = (LayoutInflater) getBaseContext()
            .getSystemService(LAYOUT_INFLATER_SERVICE);
    popupView = layoutInflater.inflate(R.layout.activity_event_create,          null);
    final PopupWindow popupWindow = new PopupWindow(
            popupView,
           400,
            LayoutParams.WRAP_CONTENT);
    View new_event_button = (View) findViewById(R.id.button);
    popupWindow.showAsDropDown(new_event_button);

   dateSpinner = (TextView) popupView.findViewById(R.id.spinner_date);

    View.OnTouchListener Spinner_OnTouch = new View.OnTouchListener() {
        public boolean onTouch(View v, MotionEvent event) {
            if (event.getAction() == MotionEvent.ACTION_UP) {
                showDatePickerDialog(v);
            }
            return true;
        }
    };
    View.OnKeyListener Spinner_OnKey = new View.OnKeyListener() {
        public boolean onKey(View v, int keyCode, KeyEvent event) {
            if (keyCode == KeyEvent.KEYCODE_DPAD_CENTER) {
                showDatePickerDialog(v);
                return true;
            } else {
                return false;
            }
        }
    };

    dateSpinner.setOnTouchListener(Spinner_OnTouch);
    dateSpinner.setOnKeyListener(Spinner_OnKey);
     SimpleDateFormat sdf = new SimpleDateFormat("cccc, MMMM dd, yyyy", Locale.US);
    dateSpinner.setText(sdf.format(myCalendar.getTime()));

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

}

Answer 1

首先您要在 DialogFragment 中创建一个接口并将数据发送到该接口。接下来，您要在活动中实现该接口的侦听器。在该侦听器中，您将设置文本。应该没有任何问题，但如果有，请告诉我，我会尽力提供帮助。

DatePickerFragment首先要在这个类中创建一个接口，然后在活动中实现它。

import android.app.Activity;
import android.app.DatePickerDialog;
import android.app.Dialog;
import android.os.Bundle;
import android.support.v4.app.DialogFragment;
import android.widget.DatePicker;

import java.util.Calendar;


public class DatePickerFragment extends DialogFragment
        implements DatePickerDialog.OnDateSetListener {

    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        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);
        return new DatePickerDialog(getActivity(), this, year, month, day);
    }


    public void onDateSet(DatePicker view, int year, int month, int day) {
        mCallbacks.setTextDate(year, month, day);
    }

    /**
     * Interface to communicate to the parent activity (MainActivity.java)
     */
    private FragmentCallbacks mCallbacks;

    public interface FragmentCallbacks {
        void setTextDate(int year, int month, int day);
    }

    @Override
    public void onAttach(Activity activity) { // Attach it to the activity
        super.onAttach(activity);
        try {
            mCallbacks = (FragmentCallbacks) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException("Activity must implement Fragment One.");
        }
    }

    @Override
    public void onDetach() { // Remove the listener
        super.onDetach();
        mCallbacks = null;
    }
}

MainActivity 确保在扩展类之后调用 implements DatePickerFragment.FragmentCallbacks！

import android.os.Bundle;
import android.support.v4.app.DialogFragment;
import android.support.v7.app.AppCompatActivity;
import android.widget.TextView;

// Make sure you implement the listener in the DatePickerFragment()
public class MainActivity extends AppCompatActivity implements DatePickerFragment.FragmentCallbacks {
    private TextView dateSpinner;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // Removed the touch listeners for this example to make it simple.
        // Show dialog on start for this example
        showDatePickerDialog();

        dateSpinner = (TextView) findViewById(R.id.spinner_date);
    }

    // Changed it to getSupportFragmentManager(),
    // You might need to change yours back to getFragmentManager()
    public void showDatePickerDialog() {
        DialogFragment newFragment = new DatePickerFragment();
        newFragment.show(getSupportFragmentManager(), "Date");
    }

    // The interface listener created in the DatePickerFragment()
    @Override
    public void setTextDate(int year, int month, int day) {
        dateSpinner.setText("Date Year: " + year);
    }
}