我正在解决最常见的数据库锁定问题。
当我的应用程序运行时，会点击api来获取数据。然后将此数据插入数据库表中。我在带有串行队列的后台线程中执行此操作。同时，如果用户按下按钮切换到下一个屏幕，则选择查询工作（在主线程上）以获取要显示的数据。这就是我遇到这个问题的关键所在。甚至应用程序有时也会崩溃。
我已经搜索过这个问题，但每当我看到关于“同步”的教程链接时，我都会看到这个问题。或使用FMDB。
由于时间不多了，有人可以帮助我提供一个简单而详细的解决方案。另外，我发布了用于插入和检索数据的代码。 Plz关心我是否在某个地方出错了。
-(void)insertIntoTable_VENUES_WithData:(NSArray*)dataArray{
sqlite3_stmt *statement = nil;
const char *dbpath = [_databasePath UTF8String];
if (sqlite3_open(dbpath, &_database) == SQLITE_OK) {
const char *sql = "INSERT OR REPLACE INTO venues (gig_date, start_time, doors_open, end_time, gig_title, main_artist, gig_type, promoter, band_members, venue, tel_no, postcode, img_url, ticket_price, booking_url, sold_out, venue_url, venue_biog, sync_flag) VALUES (?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)";
NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
[dateFormat setLocale:[[StaticHelper sharedObject] usLocale]];
if (sqlite3_prepare_v2(_database, sql, -1, &statement, NULL) == SQLITE_OK) {
for (int i=0; i<dataArray.count; i++) {
NSDictionary *dataDic = [NSDictionary dictionaryWithDictionary:[dataArray objectAtIndex:i]];
if (![[dataDic objectForKey:kGigDate] isEqual:[NSNull null]]){
NSString *dateStr = [dataDic objectForKey:kGigDate];
[dateFormat setDateFormat:@"dd/MM/yyyy"];
NSDate *dateFromString = [[NSDate alloc] init];
dateFromString = [dateFormat dateFromString:dateStr];
NSDate *dateWithoutTime = [[StaticHelper sharedObject] getDateWithOutTime:dateFromString];
float dateToStore = [dateWithoutTime timeIntervalSince1970];
sqlite3_bind_double(statement, 1, dateToStore);
}
else
sqlite3_bind_null(statement,1);
if (![[dataDic objectForKey:kStartTime] isEqual:[NSNull null]])
sqlite3_bind_text(statement,2,[[dataDic objectForKey:kStartTime] UTF8String],-1,SQLITE_TRANSIENT);
else
sqlite3_bind_null(statement,2);
if (![[dataDic objectForKey:kDoorsOpen] isEqual:[NSNull null]])
sqlite3_bind_text(statement,3,[[dataDic objectForKey:kDoorsOpen] UTF8String],-1,SQLITE_TRANSIENT);
else
sqlite3_bind_null(statement,3);
if (![[dataDic objectForKey:kEndTime] isEqual:[NSNull null]])
sqlite3_bind_text(statement,4,[[dataDic objectForKey:kEndTime] UTF8String],-1,SQLITE_TRANSIENT);
else
sqlite3_bind_null(statement,4);
if (![[dataDic objectForKey:kGigTitle] isEqual:[NSNull null]])
sqlite3_bind_text(statement,5,[[dataDic objectForKey:kGigTitle] UTF8String],-1,SQLITE_TRANSIENT);
else
sqlite3_bind_null(statement,5);
if (![[dataDic objectForKey:kMainArtist] isEqual:[NSNull null]])
sqlite3_bind_text(statement,6,[[dataDic objectForKey:kMainArtist] UTF8String],-1,SQLITE_TRANSIENT);
else
sqlite3_bind_null(statement,6);
if (![[dataDic objectForKey:kGigType] isEqual:[NSNull null]])
sqlite3_bind_text(statement,7,[[dataDic objectForKey:kGigType] UTF8String],-1,SQLITE_TRANSIENT);
else
sqlite3_bind_null(statement,7);
if (![[dataDic objectForKey:kPromoter] isEqual:[NSNull null]])
sqlite3_bind_text(statement,8,[[dataDic objectForKey:kPromoter] UTF8String],-1,SQLITE_TRANSIENT);
else
sqlite3_bind_null(statement,8);
if (![[dataDic objectForKey:kBandMembers] isEqual:[NSNull null]])
sqlite3_bind_text(statement,9,[[dataDic objectForKey:kBandMembers] UTF8String],-1,SQLITE_TRANSIENT);
else
sqlite3_bind_null(statement,9);
if (![[dataDic objectForKey:kVenue] isEqual:[NSNull null]])
sqlite3_bind_text(statement,10,[[dataDic objectForKey:kVenue] UTF8String],-1,SQLITE_TRANSIENT);
else
sqlite3_bind_null(statement,10);
if (![[dataDic objectForKey:kTelNo] isEqual:[NSNull null]])
sqlite3_bind_text(statement,11,[[dataDic objectForKey:kTelNo] UTF8String],-1,SQLITE_TRANSIENT);
else
sqlite3_bind_null(statement,11);
if (![[dataDic objectForKey:kPostCode] isEqual:[NSNull null]])
sqlite3_bind_text(statement,12,[[dataDic objectForKey:kPostCode] UTF8String],-1,SQLITE_TRANSIENT);
else
sqlite3_bind_null(statement,12);
if (![[dataDic objectForKey:kImgUrl] isEqual:[NSNull null]])
sqlite3_bind_text(statement,13,[[dataDic objectForKey:kImgUrl] UTF8String],-1,SQLITE_TRANSIENT);
else
sqlite3_bind_null(statement,13);
if (![[dataDic objectForKey:kTicketPrice] isEqual:[NSNull null]])
sqlite3_bind_text(statement,14,[[dataDic objectForKey:kTicketPrice] UTF8String],-1,SQLITE_TRANSIENT);
else
sqlite3_bind_null(statement,14);
if (![[dataDic objectForKey:kBookingUrl] isEqual:[NSNull null]])
sqlite3_bind_text(statement,15,[[dataDic objectForKey:kBookingUrl] UTF8String],-1,SQLITE_TRANSIENT);
else
sqlite3_bind_null(statement,15);
if (![[dataDic objectForKey:kSoldOut] isEqual:[NSNull null]])
sqlite3_bind_text(statement,16,[[dataDic objectForKey:kSoldOut] UTF8String],-1,SQLITE_TRANSIENT);
else
sqlite3_bind_null(statement,16);
if (![[dataDic objectForKey:kVenueUrl] isEqual:[NSNull null]])
sqlite3_bind_text(statement,17,[[dataDic objectForKey:kVenueUrl] UTF8String],-1,SQLITE_TRANSIENT);
else
sqlite3_bind_null(statement,17);
if (![[dataDic objectForKey:kVenueBlog] isEqual:[NSNull null]])
sqlite3_bind_text(statement,18,[[dataDic objectForKey:kVenueBlog] UTF8String],-1,SQLITE_TRANSIENT);
else
sqlite3_bind_null(statement,18);
sqlite3_bind_int(statement, 19, 0);////
if (sqlite3_step(statement) != SQLITE_DONE) {
NSLog(@"SQL execution failed in ZADDED_FOOD_ITEMS: %s", sqlite3_errmsg(_database));
}
if (sqlite3_step(statement) == SQLITE_DONE) {
if (i == (dataArray.count - 1))
sqlite3_finalize(statement);
}else{
sqlite3_reset(statement);
NSLog(@"SQL execution failed: %s", sqlite3_errmsg(_database));
}
}//for
sqlite3_finalize(statement);
}else{
NSLog(@"Row insertion error(error in prepare!)");
}
sqlite3_finalize(statement);//finalize is to sqlite3_prepare_v2 as close is to sqlite3_open
sqlite3_close(_database);;
}else{
NSLog(@"error in opening db");
}
}
-(NSMutableArray *)getDataFromTable_VENUES_WhereGigDateIsEqualTo:(NSDate*)gigDate
{
NSDate *dateWithoutTime = [[StaticHelper sharedObject] getDateWithOutTime:gigDate];
NSTimeInterval dateInterval = [dateWithoutTime timeIntervalSince1970] ;
NSInteger intDateInterval = dateInterval;
const char *dbpath = [_databasePath UTF8String];
NSMutableArray *queryResult = [NSMutableArray array];
sqlite3_stmt *statement = nil;
NSMutableDictionary *dic;
if (sqlite3_open(dbpath, &_database) == SQLITE_OK)
{
NSString *query = [NSString stringWithFormat:@" SELECT * FROM %@ WHERE %@='%ld' AND %@=1 ORDER BY %@ ASC ",kVenues, kGigDate, intDateInterval, kSyncFlag, kStartTime];
if(sqlite3_prepare_v2(_database,[query UTF8String],-1,&statement,NULL)==SQLITE_OK)
{
while (sqlite3_step(statement)<=SQLITE_ROW)
{
dic = [NSMutableDictionary dictionary];
float dbDataAsDouble0 = sqlite3_column_double(statement, 0);
NSDate *dateRetrieved = [NSDate dateWithTimeIntervalSince1970:dbDataAsDouble0];
NSString *strDate = [[StaticHelper sharedObject] getStringFromDate:dateRetrieved];
//char *dbDataAsChars0 = (char*)sqlite3_column_text(statement, 0);
if (strDate != nil)
[dic setObject:strDate forKey:kGigDate];
else{
[dic setObject:@"" forKey:kGigDate];
}
char *dbDataAsChars1 = (char*)sqlite3_column_text(statement, 1);
if (dbDataAsChars1 != NULL)
[dic setObject:[NSString stringWithUTF8String:dbDataAsChars1] forKey:kStartTime];
else{
[dic setObject:@"" forKey:kStartTime];
}
char *dbDataAsChars2 = (char*)sqlite3_column_text(statement, 2);
if (dbDataAsChars2 != NULL)
[dic setObject:[NSString stringWithUTF8String:dbDataAsChars2] forKey:kDoorsOpen];
else{
[dic setObject:@"" forKey:kDoorsOpen];
}
char *dbDataAsChars3 = (char*)sqlite3_column_text(statement, 3);
if (dbDataAsChars3 != NULL)
[dic setObject:[NSString stringWithUTF8String:dbDataAsChars3] forKey:kEndTime];
else{
[dic setObject:@"" forKey:kEndTime];
}
char *dbDataAsChars4 = (char*)sqlite3_column_text(statement, 4);
if (dbDataAsChars4 != NULL)
[dic setObject:[NSString stringWithUTF8String:dbDataAsChars4] forKey:kGigTitle];
else{
[dic setObject:@"" forKey:kGigTitle];
}
char *dbDataAsChars5 = (char*)sqlite3_column_text(statement, 5);
if (dbDataAsChars5 != NULL)
[dic setObject:[NSString stringWithUTF8String:dbDataAsChars5] forKey:kMainArtist];
else{
[dic setObject:@"" forKey:kMainArtist];
}
char *dbDataAsChars6 = (char*)sqlite3_column_text(statement, 6);
if (dbDataAsChars6 != NULL)
[dic setObject:[NSString stringWithUTF8String:dbDataAsChars6] forKey:kGigType];
else{
[dic setObject:@"" forKey:kGigType];
}
char *dbDataAsChars7 = (char*)sqlite3_column_text(statement, 7);
if (dbDataAsChars7 != NULL)
[dic setObject:[NSString stringWithUTF8String:dbDataAsChars7] forKey:kPromoter];
else{
[dic setObject:@"" forKey:kPromoter];
}
char *dbDataAsChars8 = (char*)sqlite3_column_text(statement, 8);
if (dbDataAsChars8 != NULL)
[dic setObject:[NSString stringWithUTF8String:dbDataAsChars8] forKey:kBandMembers];
else{
[dic setObject:@"" forKey:kBandMembers];
}
char *dbDataAsChars9 = (char*)sqlite3_column_text(statement, 9);
if (dbDataAsChars9 != NULL)
[dic setObject:[NSString stringWithUTF8String:dbDataAsChars9] forKey:kVenue];
else{
[dic setObject:@"" forKey:kVenue];
}
char *dbDataAsChars10 = (char*)sqlite3_column_text(statement, 10);
if (dbDataAsChars10 != NULL)
[dic setObject:[NSString stringWithUTF8String:dbDataAsChars10] forKey:kTelNo];
else{
[dic setObject:@"" forKey:kTelNo];
}
char *dbDataAsChars11 = (char*)sqlite3_column_text(statement, 11);
if (dbDataAsChars11 != NULL)
[dic setObject:[NSString stringWithUTF8String:dbDataAsChars11] forKey:kPostCode];
else{
[dic setObject:@"" forKey:kPostCode];
}
char *dbDataAsChars12 = (char*)sqlite3_column_text(statement, 12);
if (dbDataAsChars12 != NULL)
[dic setObject:[NSString stringWithUTF8String:dbDataAsChars12] forKey:kImgUrl];
else{
[dic setObject:@"" forKey:kImgUrl];
}
char *dbDataAsChars13 = (char*)sqlite3_column_text(statement, 13);
if (dbDataAsChars13 != NULL)
[dic setObject:[NSString stringWithUTF8String:dbDataAsChars13] forKey:kTicketPrice];
else{
[dic setObject:@"" forKey:kTicketPrice];
}
char *dbDataAsChars14 = (char*)sqlite3_column_text(statement, 14);
if (dbDataAsChars14 != NULL)
[dic setObject:[NSString stringWithUTF8String:dbDataAsChars14] forKey:kBookingUrl];
else{
[dic setObject:@"" forKey:kBookingUrl];
}
char *dbDataAsChars15 = (char*)sqlite3_column_text(statement, 15);
if (dbDataAsChars15 != NULL)
[dic setObject:[NSString stringWithUTF8String:dbDataAsChars15] forKey:kSoldOut];
else{
[dic setObject:@"" forKey:kSoldOut];
}
char *dbDataAsChars16 = (char*)sqlite3_column_text(statement, 16);
if (dbDataAsChars16 != NULL)
[dic setObject:[NSString stringWithUTF8String:dbDataAsChars16] forKey:kVenueUrl];
else{
[dic setObject:@"" forKey:kVenueUrl];
}
char *dbDataAsChars17 = (char*)sqlite3_column_text(statement, 17);
if (dbDataAsChars17 != NULL)
[dic setObject:[NSString stringWithUTF8String:dbDataAsChars17] forKey:kVenueBlog];
else{
[dic setObject:@"" forKey:kVenueBlog];
}
[queryResult addObject:dic];
}
sqlite3_finalize(statement);
}
else{
////NSLog(@"Error msg : %s ", sqlite3_errmsg(_database));
return nil;
}
sqlite3_close(_database);
}
else{
NSLog(@"database not open : %s",sqlite3_errmsg(_database));
}
return queryResult;
}
答案 0 :(得分：1)
您在任何查询之前每次都打开数据库。制作一种方法来打开数据库并在应用启动时打开您的连接。
- (void) openDatabaseConnection
{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
path = [documentsDirectory stringByAppendingPathComponent:yourDB];
if (sqlite3_open_v2([path UTF8String], &databaseName, SQLITE_OPEN_READWRITE, NULL) == SQLITE_OK)
{
NSLog(@"Data base connection opened %@",path);
}
else
{
NSLog(@"Error in opening database :(");
}
}
不要每次都打开它。它将锁定您的数据库以便频繁地打开和关闭连接。
答案 1 :(得分：1)
如果数据库已经打开并使用某个thread-process锁定，则在您尝试打开它时会出现此错误（尝试打开锁定的数据库）
在getDataFromTable_VENUES_WhereGigDateIsEqualTo方法中，请检查以下内容：
else{
////NSLog(@"Error msg : %s ", sqlite3_errmsg(_database));
return nil;
}
在这里，您在使用
解锁开放式数据库时正在撤退sqlite3_close(_database);
在返回此处之前关闭数据库。还要检查代码中其他地方的类似问题。
else{
sqlite3_close(_database);
////NSLog(@"Error msg : %s ", sqlite3_errmsg(_database));
return nil;
}
为了避免类似的错误，创建用于处理数据库函数的类并创建它的共享实例。
#import <Foundation/Foundation.h>
#import <sqlite3.h>
@interface DBManager : NSObject
{
NSString *databasePath;
}
+(DBManager*)getSharedInstance;
@end
#import "DBManager.h"
static DBManager *sharedInstance = nil;
static sqlite3 *database = nil;
static sqlite3_stmt *statement = nil;
@implementation DBManager
+(DBManager*)getSharedInstance{
if (!sharedInstance) {
sharedInstance = [[super allocWithZone:NULL]init];
[sharedInstance openDB];
}
return sharedInstance;
}
-(BOOL)openDB{
//打开数据库的代码，将其分配给database，返回状态
}