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У меня есть listview, и когда я нажимаю на элемент списка, пользователь будет перенаправлен на экран редактирования, который будет извлекать данные из базы данных с помощью курсора и заполнять в текстовых полях редактирования. Но я получаю NullPointerException, когда я выбираю элемент списка, и ошибка отображается на cursor.getColumnIndexOrThrow(), хотя БД не пуста.cursor.getColumnIndexOrThrow() throws NullPointerException
RemindersDbAdapter.java
public class RemindersDbAdapter {
private static final String DATABASE_NAME = "data";
private static final String DATABASE_TABLE = "reminders";
private static final int DATABASE_VERSION = 4;
public static final String KEY_TITLE = "title";
public static final String KEY_BODY = "body";
public static final String KEY_DATE_TIME = "reminder_date_time";
public static final String KEY_ROWID = "_id";
private static final String TAG = "ReminderDbAdapter";
private DatabaseHelper mDbHelper;
private SQLiteDatabase mDb;
Cursor mCursor;
private static final String DATABASE_CREATE = "create table "
+ DATABASE_TABLE + " (" + KEY_ROWID
+ " integer primary key autoincrement, " + KEY_TITLE
+ " text not null, " + KEY_BODY + " text not null, "
+ KEY_DATE_TIME + " text not null);";
private final Context mCtx;
private static class DatabaseHelper extends SQLiteOpenHelper {
DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(DATABASE_CREATE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
+ newVersion + ", which will destroy all old data");
db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);
onCreate(db);
}
}
public RemindersDbAdapter(Context ctx) {
this.mCtx = ctx;
}
public RemindersDbAdapter open() throws SQLException {
mDbHelper = new DatabaseHelper(mCtx);
mDb = mDbHelper.getWritableDatabase();
return this;
}
public void close() {
mDbHelper.close();
}
public long createReminder(String title, String body,
String reminderDateTime) {
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_TITLE, title);
initialValues.put(KEY_BODY, body);
initialValues.put(KEY_DATE_TIME, reminderDateTime);
return mDb.insert(DATABASE_TABLE, null, initialValues);
}
public boolean deleteReminder(long rowId) {
return mDb.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;
}
public Cursor fetchAllReminders() {
return mDb.query(DATABASE_TABLE, new String[] { KEY_ROWID, KEY_TITLE,
KEY_BODY, KEY_DATE_TIME }, null, null, null, null, null);
}
public Cursor fetchReminder(long rowId) throws SQLException {
if (mCursor != null && (mCursor.getCount() > 0)) {
mCursor = mDb.query(true, DATABASE_TABLE, new String[] { KEY_ROWID,
KEY_TITLE, KEY_BODY, KEY_DATE_TIME }, KEY_ROWID + "="
+ rowId, null, null, null, null, null);
}
if (mCursor != null && mCursor.getCount()>0)
{ mCursor.moveToFirst(); }
return mCursor;
}
public boolean updateReminder(long rowId, String title, String body,
String reminderDateTime) {
ContentValues args = new ContentValues();
args.put(KEY_TITLE, title);
args.put(KEY_BODY, body);
args.put(KEY_DATE_TIME, reminderDateTime);
return mDb.update(DATABASE_TABLE, args, KEY_ROWID + "=" + rowId, null) > 0;
}
}
ReminderEditActivity
public class ReminderEditActivity extends Activity {
//
// Dialog Constants
//
private static final int DATE_PICKER_DIALOG = 0;
private static final int TIME_PICKER_DIALOG = 1;
//
// Date Format
//
private static final String DATE_FORMAT = "yyyy-MM-dd";
private static final String TIME_FORMAT = "kk:mm";
public static final String DATE_TIME_FORMAT = "yyyy-MM-dd kk:mm:ss";
private EditText mTitleText;
private EditText mBodyText;
private Button mDateButton;
private Button mTimeButton;
private Button mConfirmButton;
private Long mRowId;
private RemindersDbAdapter mDbHelper;
private Calendar mCalendar;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mDbHelper = new RemindersDbAdapter(this);
setContentView(R.layout.reminder_edit);
mCalendar = Calendar.getInstance();
mTitleText = (EditText) findViewById(R.id.title);
mBodyText = (EditText) findViewById(R.id.body);
mDateButton = (Button) findViewById(R.id.reminder_date);
mTimeButton = (Button) findViewById(R.id.reminder_time);
mConfirmButton = (Button) findViewById(R.id.confirm);
mRowId = savedInstanceState != null ? savedInstanceState.getLong(RemindersDbAdapter.KEY_ROWID)
: null;
registerButtonListenersAndSetDefaultText();
}
private void setRowIdFromIntent() {
if (mRowId == null) {
Bundle extras = getIntent().getExtras();
mRowId = extras != null ? extras.getLong(RemindersDbAdapter.KEY_ROWID)
: null;
}
}
@Override
protected void onPause() {
super.onPause();
mDbHelper.close();
}
@Override
protected void onResume() {
super.onResume();
mDbHelper.open();
setRowIdFromIntent();
populateFields();
}
@Override
protected Dialog onCreateDialog(int id) {
switch(id) {
case DATE_PICKER_DIALOG:
return showDatePicker();
case TIME_PICKER_DIALOG:
return showTimePicker();
}
return super.onCreateDialog(id);
}
private DatePickerDialog showDatePicker() {
DatePickerDialog datePicker = new DatePickerDialog(ReminderEditActivity.this, new DatePickerDialog.OnDateSetListener() {
@Override
public void onDateSet(DatePicker view, int year, int monthOfYear, int dayOfMonth) {
mCalendar.set(Calendar.YEAR, year);
mCalendar.set(Calendar.MONTH, monthOfYear);
mCalendar.set(Calendar.DAY_OF_MONTH, dayOfMonth);
updateDateButtonText();
}
}, mCalendar.get(Calendar.YEAR), mCalendar.get(Calendar.MONTH), mCalendar.get(Calendar.DAY_OF_MONTH));
return datePicker;
}
частный TimePickerDialog showTimePicker() {
TimePickerDialog timePicker = new TimePickerDialog(this, new TimePickerDialog.OnTimeSetListener() {
@Override
public void onTimeSet(TimePicker view, int hourOfDay, int minute) {
mCalendar.set(Calendar.HOUR_OF_DAY, hourOfDay);
mCalendar.set(Calendar.MINUTE, minute);
updateTimeButtonText();
}
}, mCalendar.get(Calendar.HOUR_OF_DAY), mCalendar.get(Calendar.MINUTE), true);
return timePicker;
}
private void registerButtonListenersAndSetDefaultText() {
mDateButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
showDialog(DATE_PICKER_DIALOG);
}
});
mTimeButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
showDialog(TIME_PICKER_DIALOG);
}
});
mConfirmButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
saveState();
setResult(RESULT_OK);
Toast.makeText(ReminderEditActivity.this, getString(R.string.task_saved_message), Toast.LENGTH_SHORT).show();
finish();
}
});
updateDateButtonText();
updateTimeButtonText();
}
private void populateFields() {
// Only populate the text boxes and change the calendar date
// if the row is not null from the database.
if (mRowId != null) {
Cursor reminder = mDbHelper.fetchReminder(mRowId);
System.out.println("RowID "+mRowId);
startManagingCursor(reminder);
mTitleText.setText(reminder.getString(
reminder.getColumnIndexOrThrow(RemindersDbAdapter.KEY_TITLE)));
mBodyText.setText(reminder.getString(
reminder.getColumnIndexOrThrow(RemindersDbAdapter.KEY_BODY)));
// Get the date from the database and format it for our use.
SimpleDateFormat dateTimeFormat = new SimpleDateFormat(DATE_TIME_FORMAT);
Date date = null;
try {
String dateString = reminder.getString(reminder.getColumnIndexOrThrow(RemindersDbAdapter.KEY_DATE_TIME));
date = dateTimeFormat.parse(dateString);
mCalendar.setTime(date);
} catch (ParseException e) {
Log.e("ReminderEditActivity", e.getMessage(), e);
}
} else {
// This is a new task - add defaults from preferences if set.
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this);
String defaultTitleKey = getString(R.string.pref_task_title_key);
String defaultTimeKey = getString(R.string.pref_default_time_from_now_key);
String defaultTitle = prefs.getString(defaultTitleKey, null);
String defaultTime = prefs.getString(defaultTimeKey, null);
if(defaultTitle != null)
mTitleText.setText(defaultTitle);
if(defaultTime != null)
mCalendar.add(Calendar.MINUTE, Integer.parseInt(defaultTime));
}
updateDateButtonText();
updateTimeButtonText();
}
private void updateTimeButtonText() {
// Set the time button text based upon the value from the database
SimpleDateFormat timeFormat = new SimpleDateFormat(TIME_FORMAT);
String timeForButton = timeFormat.format(mCalendar.getTime());
mTimeButton.setText(timeForButton);
}
private void updateDateButtonText() {
// Set the date button text based upon the value from the database
SimpleDateFormat dateFormat = new SimpleDateFormat(DATE_FORMAT);
String dateForButton = dateFormat.format(mCalendar.getTime());
mDateButton.setText(dateForButton);
}
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putLong(RemindersDbAdapter.KEY_ROWID, mRowId);
}
private void saveState() {
String title = mTitleText.getText().toString();
String body = mBodyText.getText().toString();
SimpleDateFormat dateTimeFormat = new SimpleDateFormat(DATE_TIME_FORMAT);
String reminderDateTime = dateTimeFormat.format(mCalendar.getTime());
if (mRowId == null) {
long id = mDbHelper.createReminder(title, body, reminderDateTime);
if (id > 0) {
mRowId = id;
}
} else {
mDbHelper.updateReminder(mRowId, title, body, reminderDateTime);
}
/* Intent i=new Intent(ReminderEditActivity.this,ReminderService.class);
i.putExtra("title", title);
i.putExtra("description", body);
i.putExtra("date", reminderDateTime);
startService(i);*/
new ReminderManager(this).setReminder(mRowId, mCalendar);
}
}
Logcat
03-09 15:29:56.554: I/System.out(758): Reminders 1
03-09 15:29:56.733: D/gralloc_goldfish(758): Emulator without GPU emulation detected.
03-09 15:29:56.774: I/dalvikvm(758): threadid=3: reacting to signal 3
03-09 15:29:56.804: I/dalvikvm(758): Wrote stack traces to '/data/anr/traces.txt'
03-09 15:30:06.613: I/System.out(758): RowID 1
03-09 15:30:06.613: D/AndroidRuntime(758): Shutting down VM
03-09 15:30:06.623: W/dalvikvm(758): threadid=1: thread exiting with uncaught exception (group=0x409c01f8)
03-09 15:30:06.643: E/AndroidRuntime(758): FATAL EXCEPTION: main
03-09 15:30:06.643: E/AndroidRuntime(758): java.lang.RuntimeException: Unable to resume activity {com.dummies.android.taskreminder/com.dummies.android.taskreminder.ReminderEditActivity}: java.lang.NullPointerException
03-09 15:30:06.643: E/AndroidRuntime(758): \t at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2444)
03-09 15:30:06.643: E/AndroidRuntime(758): \t at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2472)
03-09 15:30:06.643: E/AndroidRuntime(758): \t at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1986)
03-09 15:30:06.643: E/AndroidRuntime(758): \t at android.app.ActivityThread.access$600(ActivityThread.java:123)
03-09 15:30:06.643: E/AndroidRuntime(758): \t at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
03-09 15:30:06.643: E/AndroidRuntime(758): \t at android.os.Handler.dispatchMessage(Handler.java:99)
03-09 15:30:06.643: E/AndroidRuntime(758): \t at android.os.Looper.loop(Looper.java:137)
03-09 15:30:06.643: E/AndroidRuntime(758): \t at android.app.ActivityThread.main(ActivityThread.java:4424)
03-09 15:30:06.643: E/AndroidRuntime(758): \t at java.lang.reflect.Method.invokeNative(Native Method)
03-09 15:30:06.643: E/AndroidRuntime(758): \t at java.lang.reflect.Method.invoke(Method.java:511)
03-09 15:30:06.643: E/AndroidRuntime(758): \t at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
03-09 15:30:06.643: E/AndroidRuntime(758): \t at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
03-09 15:30:06.643: E/AndroidRuntime(758): \t at dalvik.system.NativeStart.main(Native Method)
03-09 15:30:06.643: E/AndroidRuntime(758): Caused by: java.lang.NullPointerException
03-09 15:30:06.643: E/AndroidRuntime(758): \t at com.dummies.android.taskreminder.ReminderEditActivity.populateFields(ReminderEditActivity.java:181)
03-09 15:30:06.643: E/AndroidRuntime(758): \t at com.dummies.android.taskreminder.ReminderEditActivity.onResume(ReminderEditActivity.java:92)
03-09 15:30:06.643: E/AndroidRuntime(758): \t at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1154)
03-09 15:30:06.643: E/AndroidRuntime(758): \t at android.app.Activity.performResume(Activity.java:4539)
03-09 15:30:06.643: E/AndroidRuntime(758): \t at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2434)
03-09 15:30:06.643: E/AndroidRuntime(758): \t ... 12 more
03-09 15:30:06.893: I/dalvikvm(758): threadid=3: reacting to signal 3
03-09 15:30:06.993: I/dalvikvm(758): Wrote stack traces to '/data/anr/traces.txt'
03-09 15:30:07.013: D/dalvikvm(758): GC_CONCURRENT freed 146K, 3% free 12859K/13127K, paused 7ms+62ms
03-09 15:30:07.243: I/dalvikvm(758): threadid=3: reacting to signal 3
03-09 15:30:07.273: I/dalvikvm(758): Wrote stack traces to '/data/anr/traces.txt'
Можете ли вы опубликовать исключение? – vkislicins
Возможный дубликат [Что такое Исключение Null Указатель и как его исправить?] (Http://stackoverflow.com/questions/218384/what-is-a-null-pointer-exception-and-how-do -i-fix-it) – starkshang
@FireSun Ссылка указывает, что такое NullPointerException и как с этим бороться. Но мой вопрос специфичен для курсора Android – san9194