实际上我有两个java类，其中一个是 Activity 类。现在，从该 Activity 类中，我想调用不在 Activity 类中的第二类函数。因此，一切正常，但当我在该函数内使用 SharedPreferences 时，它显示错误 Unable to start Activity ComponentInfo java.lang.NullPointerException。请任何人帮忙。
第一个 java 文件的代码:
public class SplashScreen extends Activity
{
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.splash_screen);
CycleManager.getSingletonObject().test();//call functions of another class
}
}
第二个java文件的代码:
public class CycleManager
{
private static CycleManager cycleMangrObject;
private CycleManager() {
onInitialization();
//Compute averages using data loaded from register
ComputeAverages();
}
public static synchronized CycleManager getSingletonObject() {
if (cycleMangrObject == null) {
cycleMangrObject = new CycleManager();
}
return cycleMangrObject;
}
public Object clone() throws CloneNotSupportedException {
throw new CloneNotSupportedException();
}
public void test()
{
SharedPreferences preferences1 =getSharedPreferences("myPreferences", 0);
}
public void setAlertOnDevice(){
//Delete data
Uri EVENTS_URI = Uri.parse(getCalendarUriBase(this) + "events");
int id = 1; // calendar entry ID
ContentResolver cr = getContentResolver();
EVENTS_URI= ContentUris.withAppendedId(EVENTS_URI, id);
cr.delete(EVENTS_URI, "calendar_id=1", null);
Resources res=getResources();
//set Alerts in device calendar
Date dtStartDate = CycleManager.getSingletonObject().getStartDate();
boolean bDeleteAndReturn = false;
Calendar cal = Calendar.getInstance();
if (dtStartDate.getTime() == CycleManager.getSingletonObject().getDefaultDate().getTime())
{
bDeleteAndReturn = true;
dtStartDate = cal.getTime();
}
getOffsetsForCycleStages(CycleManager.getSingletonObject().iAvgCycleTime);
if(bDeleteAndReturn==false)
{
if (CycleManager.getSingletonObject().bNextCycleAlert && iStart>0)
{
cal.setTime(dtStartDate);
cal.add(Calendar.DATE, iStart);
// ContentResolver cr = getContentResolver();
String str=res.getString(R.string.alert_start);
String strDescription=res.getString(R.string.alert_start_msg);
ContentValues values = new ContentValues();
values.put("calendar_id", 1);
values.put("title", str);
values.put("description", strDescription);
values.put("dtstart", cal.getTimeInMillis());
values.put("dtend", cal.getTimeInMillis());
cr.insert(EVENTS_URI, values);
}
if (CycleManager.getSingletonObject().bSafeAlert)
{
if (iSafe1>0)
{
cal.setTime(dtStartDate);
cal.add(Calendar.DATE, iSafe1);
// ContentResolver cr = getContentResolver();
String str=res.getString(R.string.alert_safe);
String strDescription=res.getString(R.string.alert_safe_msg) + " " + new Integer(iUnsafe1-iSafe1-1);
ContentValues values = new ContentValues();
values.put("calendar_id", 1);
values.put("title", str);
values.put("description", strDescription);
values.put("dtstart", cal.getTimeInMillis());
values.put("dtend", cal.getTimeInMillis());
cr.insert(EVENTS_URI, values);
}
if (iSafe2>0)
{
cal.setTime(dtStartDate);
cal.add(Calendar.DATE, iSafe2);
// ContentResolver cr = getContentResolver();
String str=res.getString(R.string.alert_safe);
String strDescription=res.getString(R.string.alert_safe_msg) + " " + new Integer(CycleManager.getSingletonObject().iAvgCycleTime-iSafe2-1);
ContentValues values = new ContentValues();
values.put("calendar_id", 1);
values.put("title", str);
values.put("description", strDescription);
values.put("dtstart", cal.getTimeInMillis());
values.put("dtend", cal.getTimeInMillis());
cr.insert(EVENTS_URI, values);
}
}
if (CycleManager.getSingletonObject().bUnsafeAlert)
{
if (iUnsafe1>0)
{
cal.setTime(dtStartDate);
cal.add(Calendar.DATE, iUnsafe1);
// ContentResolver cr = getContentResolver();
String str=res.getString(R.string.alert_unsafe);
String strDescription=res.getString(R.string.alert_unsafe_msg) + " " + new Integer(iFertile-iUnsafe1-1);
ContentValues values = new ContentValues();
values.put("calendar_id", 1);
values.put("title", str);
values.put("description", strDescription);
values.put("dtstart", cal.getTimeInMillis());
values.put("dtend", cal.getTimeInMillis());
cr.insert(EVENTS_URI, values);
}
if (iUnsafe2>0)
{
cal.setTime(dtStartDate);
cal.add(Calendar.DATE, iUnsafe2);
// ContentResolver cr = getContentResolver();
String str=res.getString(R.string.alert_unsafe);
String strDescription=res.getString(R.string.alert_unsafe_msg) + " " + new Integer(iSafe2-iUnsafe2-1);
ContentValues values = new ContentValues();
values.put("calendar_id", 1);
values.put("title", str);
values.put("description", strDescription);
values.put("dtstart", cal.getTimeInMillis());
values.put("dtend", cal.getTimeInMillis());
cr.insert(EVENTS_URI, values);
}
}
if (CycleManager.getSingletonObject().bFertileAlert && iFertile>0)
{
cal.setTime(dtStartDate);
cal.add(Calendar.DATE, iFertile);
// ContentResolver cr = getContentResolver();
String str=res.getString(R.string.alert_fertile);
String strDescription=res.getString(R.string.alert_fertile_msg) + " " + new Integer(iUnsafe2-iFertile-1);
ContentValues values = new ContentValues();
values.put("calendar_id", 1);
values.put("title", str);
values.put("description", strDescription);
values.put("dtstart", cal.getTimeInMillis());
values.put("dtend", cal.getTimeInMillis());
cr.insert(EVENTS_URI, values);
}
if (CycleManager.getSingletonObject().bPMSAlert)
{
cal.setTime(dtStartDate);
cal.add(Calendar.DATE, iStart-7);
// ContentResolver cr = getContentResolver();
String str=res.getString(R.string.alert_pms);
String strDescription=res.getString(R.string.alert_pms_msg);
ContentValues values = new ContentValues();
values.put("calendar_id", 1);
values.put("title", str);
values.put("description", strDescription);
values.put("dtstart", cal.getTimeInMillis());
values.put("dtend", cal.getTimeInMillis());
cr.insert(EVENTS_URI, values);
}
}
}
private String getCalendarUriBase(Activity act){
String calendarUriBase = null;
Uri calendars = Uri.parse("content://calendar/calendars");
Cursor managedCursor = null;
try
{
managedCursor = act.managedQuery(calendars, null, null, null, null);
}
catch (Exception e) {}
if (managedCursor != null)
{
calendarUriBase = "content://calendar/";
}
else
{
calendars = Uri.parse("content://com.android.calendar/calendars");
try
{
managedCursor = act.managedQuery(calendars, null, null, null, null);
}
catch (Exception e){}
if (managedCursor != null)
{
calendarUriBase = "content://com.android.calendar/";
}
}
return calendarUriBase;
}
最佳答案
这是不可能的，因为另一个类不知道有一个叫做 SharedPreference 的东西..所以
public void test(Context c)
{
SharedPreferences preferences1 =c.getSharedPreferences("myPreferences", 0);
}
通话时
CycleManager.getSingletonObject().test(this);//call functions of another class
再一次
c.getContentResolver().delete(EVENTS_URI, null, null);
关于android - 无法启动 Activity ComponentInfo java.lang.NullPointerException，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/6922495/