我正在使用FMDB，当我想要返回一些值时，我正在使用FMDatabase，而当我不需要返回任何值时，我会使用FMDatabaseQueue。当我添加到数据库并且我使用FMDatabaseQueue时我没有错误（除非我在删除数据库时创建一个新数据库，然后创建[没有数据库要删除所以它创建一个新数据库]）。问题是当我用相同的database更新我的FMDatabaseQueue时我有一个错误：
最终确定或重置语句时出现未知错误（5：数据库已锁定）
数据库查询：UPDATE traps_table SET dist = 34721.853417，dist_to_close_point = 35734.768293 WHERE _id = 10
当我在数据库文件本身上尝试查询时，我没有错误，一切都很顺利。
代码如下：
- (void)updateTrapInDatabase:(FMDatabase*)db distance:(double)distance trapID:(int)trapID distanceToClosePoint:(double)distanceToClosePoint
{
NSString *statment = [NSString stringWithFormat:@"UPDATE %@ SET %@=?, %@=? WHERE %@=?", TRAP_TABLE, DISTANCE, DISTANCE_TO_CLOSE_POINT, ID];
BOOL update = [db executeUpdate:statment, @(distance), @(distanceToClosePoint), @(trapID)];
NSLog(@"Update trapID: %i, success: %@", trapID, update?@"YES":[NSString stringWithFormat:@"NO: %@", [db lastErrorMessage]]);
}
函数引用的代码：
- (void)UpdateDistanceToTrap_currentLocation:(CLLocation*)currentLocation old_location:(CLLocation*)old_location theAzimuth:(double)theAzimuth theSpeed:(double)theSpeed
{
NSLog(@"UpdateDistanceToTrap()");
__block double latColumn, lonColumn, idColumn, closePointLatColumn, closePointLonColumn, alarmDistanceColumn;
__block int _id = -1, alarmDistance = -1;
__block double distance;
__block CLLocation *trap_location = nil;
__block NSString *sqlStatment = [NSString stringWithFormat:@"SELECT * FROM %@", TRAP_TABLE];
FMResultSet *query = [trapsDB.db executeQuery:sqlStatment];
if ([query next]) {
latColumn = [query doubleForColumn:LAT];
lonColumn = [query doubleForColumn:LON];
closePointLatColumn = [query doubleForColumn:CLOSE_POINT_LAT];
closePointLonColumn = [query doubleForColumn:CLOSE_POINT_LON];
idColumn = [query intForColumn:@"_id"];
alarmDistanceColumn = [query intForColumn:ALARMDISTANCE];
do {
_id = [query intForColumn:@"_id"];
alarmDistance = [query intForColumn:ALARMDISTANCE];
if ([old_location distanceFromLocation:currentLocation] > kDISTANCE_THRESHOLD_FOR_CHECK_LOCATIONS) {
trap_location = [[CLLocation alloc] initWithLatitude:[query doubleForColumn:LAT]
longitude:[query doubleForColumn:LON]];
distance = [trap_location distanceFromLocation:currentLocation];
if (distance < alarmDistance + [ref integerForKey:@"DISTANCE_OFFSET"]) {
[trapsDB enterOrOutFromArea_operation:kENTER andTrapID:_id];
[self startSaveOnMyLocations:currentLocation.coordinate.latitude
lon:currentLocation.coordinate.longitude
time:CreateDate()
speed:theSpeed
azimuth:theAzimuth
trapID:_id];
}
else {
if ([trapsDB isEnterToArea_trapID:_id] == kENTER) {
[self startPostXml:_id];
[trapsDB enterOrOutFromArea_operation:kOUT andTrapID:_id];
}
}
}
if ([query doubleForColumn:CLOSE_POINT_LAT] != 0.0 || [query doubleForColumn:CLOSE_POINT_LAT] != 0) {
trap_location = [[CLLocation alloc] initWithLatitude:[query doubleForColumn:CLOSE_POINT_LAT]
longitude:[query doubleForColumn:CLOSE_POINT_LON]];
double distanceToClosePoint = [trap_location distanceFromLocation:currentLocation];
trap_location = [[CLLocation alloc] initWithLatitude:[query doubleForColumn:LAT]
longitude:[query doubleForColumn:LON]];
distance = [trap_location distanceFromLocation:currentLocation];
[trapsDB updateTrapInDatabase:trapsDB.db distance:distance trapID:_id distanceToClosePoint:distanceToClosePoint];
}
else {
trap_location = [[CLLocation alloc] initWithLatitude:[query doubleForColumn:LAT]
longitude:[query doubleForColumn:LON]];
distance = [trap_location distanceFromLocation:currentLocation];
[trapsDB updateTrapInDatabase:trapsDB.db distance:distance trapID:_id distanceToClosePoint:distance];
}
} while ([query next]);
}
}
我的代码有什么问题？
编辑：
trap service.妈妈:
- (void)UpdateDistanceToTrap_currentLocation:(CLLocation*)currentLocation old_location:(CLLocation*)old_location theAzimuth:(double)theAzimuth theSpeed:(double)theSpeed;
#define trapsDB ([SQLiteHandler sharedDatabase])
SQLiteHandler.m：
@property (strong, nonatomic) FMDatabase *db;
- (void)updateTrapInDatabase:(FMDatabase *)db distance:(double)distance trapID:(int)trapID distanceToClosePoint:(double)distanceToClosePoint;
编辑-2：更新了我的固定代码。
你在inDatabase调用内，迭代SELECT语句，然后你尝试做另一个inDatabase调用。如果您要这样做，您可能希望将FMDatabase作为参数传递给方法，而不是再次调用inDatabase：
- (void)updateTrapInDatabase:(FMDatabase *)db distance:(double)distance trapID:(int)trapID distanceToClosePoint:(double)distanceToClosePoint
{
NSString *sqlStatment = [NSString stringWithFormat:@"UPDATE %@ SET %@=?, %@=? WHERE %@=?", TRAP_TABLE, DISTANCE, DISTANCE_TO_CLOSE_POINT, ID];
BOOL update = [db executeUpdate:sqlStatment, @(distance), @(distanceTpClosePoint), @(trapID)];
NSLog(@"Update trapID: %i, success: %@", trapID, update?@"YES":[NSString stringWithFormat:@"NO: %@", [db lastErrorMessage]]);
}
并将您的电话换成：
[trapsDB updateTrapDistance:distance andTrapID:_id andDistanceToClosePoint:distanceToClosePoint];
有：
[trapsDB updateTrapInDatabase:db distance:distance trapID:_id distanceToClosePoint:distanceToClosePoint];
（顺便说一句，在SQL中使用?占位符通常是谨慎的（避免与float变量的精度相关问题，避免SQL注入问题和引用NSString变量的问题），所以我也调整了上面的SQL。另外，如果是SQL语句失败了，我总是记录lastErrorMessage，否则我只是猜测SQL失败的原因。根据你的需要使用或忽略这些无关的调整。）
但重点是，人们不应该在inDatabase中调用inDatabase。然而，令人好奇的是，在inDatabase中调用inDatabase通常会导致死锁，而不是“数据库被锁定”错误。坦率地说，FMDatabaseQueue的整个目的是调解来自不同线程的数据库请求，以便数据库永远不会忙碌。如果您有多个FMDatabaseQueue或FMDatabase对象，那么您通常会收到“数据库被锁定”错误的唯一时间。您的应用程序应该只在任何给定时间打开一个数据库对象。
对我来说，关闭FMResultSet解决了我的问题，例如：
- (BOOL)checkKeepAccounts {
NSString *sql = [NSString stringWithFormat:@"SELECT COUNT(*) FROM %@ where checked is 1", kGoodsListTable];
FMResultSet *s = [self.database executeQuery:sql];
int count = 0;
if ([s next]) {
count = [s intForColumnIndex:0];
}
**// This is the key**
[s close];
return count == 0;
}
不确定这对你有用，但我认为值得分享。