android 4 - 对话框片段 - 空指针异常

Question

我有一个Android 4和我的对话框片段的问题。我可以打开Dialogs，但是如果我取消对话框或每次提交时都会提交NullPointerException。在更新的Android版本，如5或6，一切都很好。 这很烦人。为什么google为什么？我搜索了多天，并测试了一些东西，但我无法得到这个工作。

public class BirthdatePickerDialogFragment extends DialogFragment implements DatePickerDialog.OnDateSetListener { 

//region Variables 



//Listener Object 
private BirthdatePickerDialogFragment.OnCompleteBabyBirthdateListener setDateListener; 

Context sourceActivityContext = null; 

//endregion 



@Override 
public Dialog onCreateDialog(Bundle savedInstanceState) { 

    String savedBirthdateString = SharedPreferenceHelper.getSharedPreferenceString(sourceActivityContext,SharedPreferenceHelper.Birthdate,""); 

    int year = 0; 
    int month = 0; 
    int day = 0; 


    if(savedBirthdateString != "") 
    { 
     String[] splitBirthdateString = savedBirthdateString.split("\\."); 


     int strYear = Integer.parseInt(splitBirthdateString[2]); 
     int strMonth = (Integer.parseInt(splitBirthdateString[1])) - 1 ; 
     int strDay = Integer.parseInt(splitBirthdateString[0]); 

     Calendar c = Calendar.getInstance(); 
     c.set(strYear,strMonth,strDay); 


     year = c.get(Calendar.YEAR); 
     month = c.get(Calendar.MONTH); 
     day = c.get(Calendar.DAY_OF_MONTH); 

    }   
    else{ 
     // Use the current date as the default date in the picker 
     final Calendar c = Calendar.getInstance(); 
     year = c.get(Calendar.YEAR); 
     month = c.get(Calendar.MONTH); 
     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 dayOfMonth) { 
    String strYear = String.valueOf(year); 
    String strDayOfMonth = String.valueOf(dayOfMonth); 
    String strMonth = String.valueOf(month + 1); 

    setDateListener.onCompleteBirthDatePicker(MessageFormat.format("{0}.{1}.{2}", strDayOfMonth, strMonth, strYear)); 
} 


public static interface OnCompleteBabyBirthdateListener { 
    public abstract void onCompleteBirthDatePicker(String babyBirthDate); 

} 

@Override 
public void onAttach(Context context) { 
    super.onAttach(context); 

    try { 
     this.setDateListener = (BirthdatePickerDialogFragment.OnCompleteBabyBirthdateListener)context; 
     this.sourceActivityContext = context; 
    } 
    catch (final ClassCastException e) { 
     throw new ClassCastException(context.toString() + " must implement OnCompleteListener"); 
    }  

} 

}

这是出生日期对话框。它打开，但如果我提交或取消引发的异常。 我希望有人能帮助我。 Exceptionlog：

E/AndroidRuntime: FATAL EXCEPTION: main 
       java.lang.NullPointerException 
        at com.jalbmagic.test.Dialogs.BirthdatePickerDialogFragment.onDateSet(BirthdatePickerDialogFragment.java:93) 
        at android.app.DatePickerDialog.tryNotifyDateSet(DatePickerDialog.java:148) 
        at android.app.DatePickerDialog.onStop(DatePickerDialog.java:155) 
        at android.app.Dialog.dismissDialog(Dialog.java:326) 
        at android.app.Dialog.dismiss(Dialog.java:302) 
        at android.app.Dialog.cancel(Dialog.java:1104) 
        at android.app.Dialog.onTouchEvent(Dialog.java:617) 
        at android.app.Dialog.dispatchTouchEvent(Dialog.java:739) 
        at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1873) 
        at android.view.View.dispatchPointerEvent(View.java:7307) 
        at android.view.ViewRootImpl.deliverPointerEvent(ViewRootImpl.java:3174) 
        at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:3119) 
        at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:4155) 
        at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:4134) 
        at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:4226) 
        at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:171) 
        at android.os.MessageQueue.nativePollOnce(Native Method) 
        at android.os.MessageQueue.next(MessageQueue.java:125) 
        at android.os.Looper.loop(Looper.java:124) 
        at android.app.ActivityThread.main(ActivityThread.java:4745) 
        at java.lang.reflect.Method.invokeNative(Native Method) 
        at java.lang.reflect.Method.invoke(Method.java:511) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
        at dalvik.system.NativeStart.main(Native Method) 

Answer 1

，我发现我的问题取代。从API Level 23开始，onAttach（Activity activity）方法被交换，新版本onAttach（Context context）。 我一直使用Android 6进行测试，并且只在onAttach（上下文上下文）上实现，所以较低的API级别，然后23不能使用此方法，我从不将活动附加到片段。所以问题很清楚。在我实施旧的方法后，一切正常。

Answer 2

尝试与此

if(!savedBirthdateString.equals("")) 
{ 
    String[] splitBirthdateString = savedBirthdateString.split("\\."); 


    int strYear = Integer.parseInt(splitBirthdateString[2]); 
    int strMonth = (Integer.parseInt(splitBirthdateString[1])) - 1 ; 
    int strDay = Integer.parseInt(splitBirthdateString[0]); 

    Calendar c = Calendar.getInstance(); 
    c.set(strYear,strMonth,strDay); 


    year = c.get(Calendar.YEAR); 
    month = c.get(Calendar.MONTH); 
    day = c.get(Calendar.DAY_OF_MONTH); 

}   
else{ 
    // Use the current date as the default date in the picker 
    final Calendar c = Calendar.getInstance(); 
    year = c.get(Calendar.YEAR); 
    month = c.get(Calendar.MONTH); 
    day = c.get(Calendar.DAY_OF_MONTH); 

}