如何调用在 Activity 中扩展 DialogFragment 的 class 的成员函数

Question

我编写了自定义 DatePickerDialog，它扩展了 DialogFragment 并实现了 DatePickerDialog.OnDateSetListener.

public class DatePickerFragment extends DialogFragment implements DatePickerDialog.OnDateSetListener {

  @Override
  public Dialog onCreateDialog(Bundle savedInstanceState) {
    DatePickerDialog dpd = new DatePickerDialog(getActivity(),
                R.style.MyDialogTheme, this, year, month, day);
    return dpd;
  }

  public void onDateSet(DatePicker view, int year, int month, int day) {

  }

  // own  methods
  String getFormattedDate() {
  }
}

我在我的 MainActivity 中调用这个片段。

public class Booking_activity extends AppCompatActivity implements View.OnClickListener {

  public void onClick(View view) {
    if (view == imgView_from) {
      // Initialize a new date picker dialog fragment
      DialogFragment dFragment = new DatePickerFragment();
      // Show the date picker dialog fragment
      dFragment.show(getFragmentManager(), "Date Picker");

      // error 
      dFragment.getFormattedDate();
    } 
  } 
}

Answer 1

您需要初始化一个新的日期选择器对话框片段：

DatePickerFragment dFragment = new DatePickerFragment();

就像下面的代码：

public class Booking_activity extends AppCompatActivity implements View.OnClickListener {
  public void onClick(View view) {
    if (view == imgView_from) {

      // Initialize a new date picker dialog fragment
      DatePickerFragment dFragment = new DatePickerFragment(); // Changed this

      // Show the date picker dialog fragment
      dFragment.show(getFragmentManager(), "Date Picker");

      // error 
        dFragment.getFormattedDate();
    } 
  }
}

Answer 2

您可以通过简单地转换对象来调用成员函数，如下所示

((DatePickerDialog)dFragment).getFormattedDate();

Answer 3

将您的函数 getFormattedDate 访问模式设为 public，如下所示

  public String getFormattedDate() {
        }

将解决您的问题。

Answer 4

错误发生是因为您试图从 DialogFragment 访问一个无效的方法。您需要使用以下内容创建 DatePickerFragment：

DatePickerFragment dFragment = new DatePickerFragment();

或铸造它：

DialogFragment dFragment = new DatePickerFragment();
((DatePickerDialog)dFragment).getFormattedDate();

但是主要缺陷是，您尝试在 dFragment 对象之前访问 getFormattedDate() method完成实例化。请记住 show() 是一个异步调用。

所以当 dFragment 完成实例化时，您需要通知 Booking_activity activity。您可以为它使用一个接口。类似于以下内容：

在你的 DatePickerFragment 中，添加接口：

public class DatePickerFragment extends DialogFragment implements DatePickerDialog.OnDateSetListener {

  private DatePickerListener mListener;

  public interface DatePickerListener {
    void onDialogFinishInitialized();
  }

  @Override
  public Dialog onCreateDialog(Bundle savedInstanceState) {
    DatePickerDialog dpd = new DatePickerDialog(getActivity(),
            R.style.MyDialogTheme, this, year, month, day);

    // you need to inform the activity when Dialog has finish
    // initialized.
    mListener.onDialogFinishInitialized();

    return dpd;
  }

  ...

  // Need to add the activity as the listener.
  @Override 
  public void onAttach(Activity activity) {
    super.onAttach(activity);
    // This makes sure that the container activity has implemented
    // the listener interface. If not, it throws an exception
    try {
      mListener = (DatePickerListener) activity;
    } catch (ClassCastException e) {
      throw new ClassCastException(activity.toString() + " must implement DatePickerListener");
    }
  }

  ...

}

在您的 Activity 中实现接口并调用 getFormattedDate() 方法：

public class Booking_activity extends AppCompatActivity
implements View.OnClickListener, DatePickerFragment.DatePickerListener {
  ...
  private DatePickerFragment dFragment;
  ...
  @Override
  public void onDialogFinishInitialized() {
    // You can call the method here now
    dFragment.getFormattedDate();
  }
  ...
}

Answer 5

所选解决方案运行良好，但我想指出 onAttach() 函数已被弃用。我在这里找到了一些解决方案：

我认为最受欢迎的答案是：

@Override
public void onAttach(Context context) {
    super.onAttach(context);
    activity = getActivity();
}

他们正在将 onAttach(Activity activity) 更改为 onAttach(Context context)。

如何调用在 Activity 中扩展 DialogFragment 的 class 的成员函数

How to call member function of a class that extend DialogFragment in an Activity

java

android

android-dialogfragment