在Android应用中设置日期时发生NullPointerException

如何解决在Android应用中设置日期时发生NullPointerException

我正在遵循此tutorial来实现点击编辑文本的日期和时间。

    import pickle
import os
#defining save,add any variables to this that you want to save following the same format
def save():
    pickle.dump(race,open(r'C:\Users\%username%\Desktop\test\race.dat','wb'))
    print("Saved!")
    return
#checking if a save file already exists
race_exist=os.path.isfile(r'C:\Users\%username%\Desktop\test\race.dat')
#if the save file exists,start from here
if race_exist==True:
    race=pickle.load(open(r'C:\Users\%username%\Desktop\test\race.dat','rb'))
    if race=='human':
        direction=input("You arrive at a crossroads during your travel,would you like to go left or right")
        if direction=='save':
            save()
    else:print('someone stabbed you because theyre racist.')
#if save file does not exist,start from here:
elif race_exist==False:
    race=input("Are you an orc or human?")
    pickle.dump(race,'wb'))
    if race=='orc':
        print("People dislike orcs,you get stabbed during your sleep and die!")
    elif race=='human':
        direction=input("You arrive at a crossroads during your travel,would you like to go left or right")
        if direction=='save':
            save()

我可以在public class LoadActivity extends AppCompatActivity { @SuppressLint("StaticFieldLeak") static EditText DateEdit; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_load); Toolbar toolbar = findViewById(R.id.toolbar); setSupportActionBar(toolbar); EditText startTimeEditText = (EditText) findViewById(R.id.start_time); startTimeEditText.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { showTruitonTimePickerDialog(v); showTruitonDatePickerDialog(v); } }); } // end onCreate public void showTruitonDatePickerDialog(View v) { DialogFragment newFragment = new DatePickerFragment(); newFragment.show(getSupportFragmentManager(),"datePicker"); } public static class DatePickerFragment extends DialogFragment implements DatePickerDialog.OnDateSetListener { @NonNull @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(requireActivity(),this,year,month,day); } } @SuppressLint("SetTextI18n") public void onDateSet(DatePicker view,int year,int month,int day) { // Do something with the date chosen by the user DateEdit.setText(day + ":" + (month + 1) + ":" + year); } }// end main class 中看到日期片段，但是当我按下app按钮时，应用崩溃了，并且出现了错误

java.lang.NullPointerException：尝试在空对象引用上调用虚拟方法'void android.widget.EditText.setText（java.lang.CharSequence）' 在com.thumbsol.accuratemobileassetsmanagament.LoadActivity $ DatePickerFragment.onDateSet（LoadActivity.java:300） 在android.app.DatePickerDialog.onClick（DatePickerDialog.java:134）

行号ok是300

如何摆脱这个错误？任何帮助将不胜感激。

解决方法

您仅定义static EditText DateEdit，并且还需要通过findViewById来获取它。 例如：

DateEdit = (EditText) findViewById(R.id.date_edit);

,

那是因为您没有在代码中的任何地方设置DateEdit的值。

提示：尽量不要将视图用​​作静态视图。可能会导致泄漏。