我正在使用FMDB，FMDatabase当我想返回一些值时，以及FMDatabaseQueue当我不需要返回任何值时，我都在使用。当我添加到数据库并使用时，FMDatabaseQueue我没有任何错误（除非在删除数据库然后创建[没有要删除的数据库，以便创建一个新数据库]的开始时创建新数据库）。问题是当我database用相同的内容更新我时FMDatabaseQueue出现错误：
未知错误完成或重置语句（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
当我尝试对数据库文件本身进行查询时，我没有收到任何错误，并且一切顺利。
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]]);
}
该函数引用的代码：
- (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：
TrapService.mm：
- (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。
您正在inDatabase通话中，遍历SELECT语句，然后尝试进行另一个inDatabase通话。如果要执行此操作，则可能需要将FMDatabase作为参数传递给方法，而不要inDatabase再次调用：
- (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]]);
}
并替换为：
[trapsDB updateTrapDistance:distance andTrapID:_id andDistanceToClosePoint:distanceToClosePoint];
与：
[trapsDB updateTrapInDatabase:db distance:distance trapID:_id distanceToClosePoint:distanceToClosePoint];
（顺便说一句，?在您的SQL中通常使用占位符（避免与float变量相关的精度问题，避免SQL注入问题和NSString变量引用问题），因此我也对上述SQL进行了调整。此外，如果SQL语句失败，我始终记录日志lastErrorMessage，否则我只是在猜测SQL为什么失败。请根据需要使用或忽略这些无关的调整。）
但是主要的一点是，inDatabase在已经进入通话状态的时候不要打电话inDatabase。不过，令人好奇的是，通常inDatabase在已经存在的inDatabase情况下进行调用会导致死锁，而不是“数据库已锁定”错误。坦白地说，的全部目的FMDatabaseQueue是调解来自不同线程的数据库请求，以使数据库永远不会繁忙。你通常会得到唯一的一次“数据库被锁定”如果你有一个以上的错误FMDatabaseQueue或FMDatabase对象。您的应用在任何给定时间都只能打开一个数据库对象。
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