我尝试制作包含事件和邀请朋友的Android应用程序，所以当我开始活动时，一开始就创建好的所有因为我的静态变量 StaticAppointment.friendContactList.size() 坚持null （之前在活动中初始化），然后当我点击此活动上的按钮是，它将带我登录激活并授予Facebook创建和事件的许可，在Facebook上授予权限后按OK我假设它会将数据恢复到我的活动onActivityResults()＆lt; - CMIIW ，然后我的活动突然重启，因此我的var StaticAppointment.friendContactList.size() null再次 ..
我的问题是这是怎么发生的？当我的活动重启或者我不知道简历可能时，避免我的变量的可能解决方案是 not null ？请问我是开发Android应用程序的新手，抱歉我的英语不好因为我是亚洲人...而且还有帮助... ...
这是错误：
12-19 08:27:15.257: E/AndroidRuntime(8311): FATAL EXCEPTION: main
12-19 08:27:15.257: E/AndroidRuntime(8311): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.pjb.meetapps2/com.pjb.meetapps2.ConfirmationActivity}: java.lang.NullPointerException
12-19 08:27:15.257: E/AndroidRuntime(8311): Caused by: java.lang.NullPointerException
12-19 08:27:15.257: E/AndroidRuntime(8311): at com.pjb.meetapps2.ConfirmationActivity.onCreate(ConfirmationActivity.java:101)
这是活动（对不起，我的活动很长，我已经削减了一些不相关的部分）：
public class ConfirmationActivity extends Activity {
// =================================
// Variables
// =================================
/*
* Data
*/
private String nameAppnt = "";
private String descAppnt = "";
public int dateAppointment = -1;
public int monthAppointment = -1;
public int yearAppointment = -1;
public int hourAppointment = -1;
public int minuteAppointment = -1;
private List<Friend> friendContactList = null;
private int alarmAppnt = -1;
private boolean fbSharing = false;
private boolean smsSharing = false;
private String[] itemsFriends;
private AppointmentDAO mDao;
/*
* Views
*/
private TextView lblName;
private TextView lblDateTime;
private TextView lblAlarm;
private TextView lblFB;
private TextView lblSMS;
private Button btnShowFriend;
private Button btnYes;
private Button btnNo;
private EditText txtDesc;
private SmsManager smsMgr;
/*
* Alarm
*/
AlarmManager alarmManager;
// =================================
// Activity Life Cycle Methods
// =================================
public static final String APP_ID = "385248281609371";
protected static final String TAG = "Meets";
String message ="";
private String[] dataId;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.confirmation);
//this is line 101 the error
itemsFriends = new String[StaticAppointment.friendContactList.size()];
lblName = (TextView) findViewById(R.id.txtConfName);
lblDateTime = (TextView) findViewById(R.id.txtConfDateTime);
lblAlarm = (TextView) findViewById(R.id.txtConfAlarm);
lblFB = (TextView) findViewById(R.id.txtConfFacebook);
lblSMS = (TextView) findViewById(R.id.txtConfSMS);
btnShowFriend = (Button) findViewById(R.id.btnConfShowFriend);
btnYes = (Button) findViewById(R.id.btnConfYes);
btnNo = (Button) findViewById(R.id.btnConfNo);
txtDesc = (EditText) findViewById(R.id.txtConfDesc);
mDao = new AppointmentDAO(this);
mDao.openConnection();
smsMgr = SmsManager.getDefault();
btnYes.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
actionYes();
}
});
@Override
protected void onResume() {
if (mDao != null)
mDao.openConnection();
super.onResume();
}
@Override
protected void onRestart() {
if (mDao != null)
mDao.openConnection();
super.onRestart();
}
@Override
protected void onPause() {
if (mDao != null)
mDao.closeConnection();
super.onPause();
}
@Override
public void onBackPressed() {
// TODO Auto-generated method stub
super.onBackPressed();
}
这是actionyes方法：
private void actionYes() {
int id = 0;
if (!StaticAppointment.isEditMode) {
int lastId = mDao.getMaxID();
if (lastId < 0) {
lastId = 0;
}
id = ++lastId;
} else {
id = StaticAppointment.currentAppointment.id;
}
StaticAppointment.currentAppointment = new Appointment();
StaticAppointment.currentAppointment.id = id;
StaticAppointment.currentAppointment.nameAppointment = nameAppnt;
StaticAppointment.currentAppointment.descAppointment = descAppnt;
StaticAppointment.currentAppointment.dateAppointment = StaticAppointment.dateAppointment;
StaticAppointment.currentAppointment.monthAppointment = StaticAppointment.monthAppointment;
StaticAppointment.currentAppointment.yearAppointment = StaticAppointment.yearAppointment;
StaticAppointment.currentAppointment.hourAppointment = StaticAppointment.hourAppointment;
StaticAppointment.currentAppointment.minuteAppointment = StaticAppointment.minuteAppointment;
StaticAppointment.currentAppointment.friendContactList = StaticAppointment.friendContactList;
StaticAppointment.currentAppointment.alarmMinutes = StaticAppointment.alarmMinutes;
StaticAppointment.currentAppointment.fbSharing = StaticAppointment.fbSharing;
StaticAppointment.currentAppointment.smsSharing = StaticAppointment.smsSharing;
StaticAppointment.currentAppointment.locationName = StaticAppointment.locationName;
StaticAppointment.currentAppointment.longitude = StaticAppointment.longitude;
StaticAppointment.currentAppointment.latitude = StaticAppointment.latitude;
StaticAppointment.currentAppointment.fbEventid = StaticAppointment.fbEventId;
for (int i = 0; i < friendContactList.size(); i++) {
friendContactList.get(i).id = StaticAppointment.currentAppointment.id;
}
StaticAppointment.friendContactList = this.friendContactList;
dateTime = dateAppointment + "-" + (monthAppointment + 1) + "-"
+ yearAppointment + ", " + hourAppointment + ":"
+ minuteAppointment;
if (StaticAppointment.currentAppointment.fbSharing) {
System.out.println("fb sharing nyala");
try {
postToFB();
} catch (Exception e) {
e.printStackTrace();
}
} else {
StaticAppointment.currentAppointment.fbEventid = "noFB";
if (StaticAppointment.currentAppointment.smsSharing) {
System.out.println("sms sharing nyala");
sendSms("noFB");
}
dbAction();
}
clearTempData();
}
，这是facebook权限：
private void postToFB() {
//System.out.println("BURUK tidak bisa login");
//Utility.showAlert(this, "Warning", "You must first log in.");
List<String> permission = new ArrayList<String>();
permission.add("publish_stream");
permission.add("create_event");
permission.add("publish_checkins");
Session session = Session.getActiveSession();
if (session != null){
// Check for publish permissions
List<String> permissions = session.getPermissions();
if (!isSubsetOf(permission, permissions)) {
Session.NewPermissionsRequest newperreq = new Session.NewPermissionsRequest(this, permission);
session.requestNewPublishPermissions(newperreq);
}
// doGetEvent();
checkIn();
}
}