無法從類實例調用方法Android

我創建了一個更新類變量的類。我創建了一個新的類實例，然後試圖調用get方法。但是我得到了'canno't解決方法錯誤，我不知道爲什麼。無法從類實例調用方法Android

public static 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); 
    } 
    int selectedDate; 
    public void onDateSet(DatePicker view, int year, int month, int day) { 
     // Do something with the date chosen by the user 
     selectedDate = day+month+year; 
    } 
    public int getSelectedDate() { 
     return selectedDate; 
    } 

} 
public void showDatePickerDialog(View view) { 
    DialogFragment newFragment = new DatePickerFragment(); 
    newFragment.show(getFragmentManager(), "datePicker"); 
    int output = newFragment.getSelectedDate(); 
}

來源

2014-03-19 David Finder

也發佈logcat錯誤。 –

哪種方法引發錯誤？顯示你的logcat。 – Piyush

哪種方法無法解決？ – donfuxx

的錯誤是在這裏：

public void showDatePickerDialog(View view) { 
    DialogFragment newFragment = new DatePickerFragment(); 
    newFragment.show(getFragmentManager(), "datePicker"); 
    int output = newFragment.getSelectedDate(); 
}

您的變量newFragment是DialogFragment。所以，你必須轉換的變量或者改變這樣的聲明：

DatePickerFragment newFragment = new DatePickerFragment();

或

int output = ((DatePickerFragment)newFragment).getSelectedDate();

編輯：爲得到你必須使用監聽器選定的日期，而不是同步方法。所以你必須以這種方式來改變你的代碼：

public static class DatePickerFragment extends DialogFragment 
implements DatePickerDialog.OnDateSetListener { 
private MyListener listener; 
public DatePickerFragment(MyListener listener){ 
    this.listener = listener; 
} 

@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); 
} 
int selectedDate; 
public void onDateSet(DatePicker view, int year, int month, int day) { 
    // Do something with the date chosen by the user 
    selectedDate = day+month+year; 
    if(listener!=null){ 
     listener.theDateHasChanged(selectedDate); 
    } 
} 
public int getSelectedDate() { 
    return selectedDate; 
}

然後你的活動必須實現MyListener接口和實現theDateHasChanged和最終你必須實例您從您的activity所以fragment：

DatePickerFragment newFragment = new DatePickerFragment(this);

來源

2014-03-19 13:52:39

好，所以代碼工作。謝謝。我在做什麼？我的理解是，該方法將返回一個int，然後可以將其傳遞給變量。 –

檢查出：我已更新我的回答 –

您能推薦一個好的資源嗎？我不清楚爲什麼我要使用一個監聽器。方法的重點不在於處理選定的日期嗎？ –

-1

也許這是因爲你的班級是靜態的。在java中，你不能創建一個定義爲靜態的類的實例。對於靜態類，您可以直接使用。（）;

DatePickerFragment.show(getFragmentManager(),"datePicker");

希望這會有所幫助。 :)

來源

2014-03-19 13:54:22 Aradhna

無法從類實例調用方法Android

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