iphone - 我无法读取我预先存在的 sqlite 数据库

Question

我已将预填充的 sqlite 数据库从捆绑包复制到库路径。现在，当我尝试执行查询时，它不会读取数据库。

复制数据库的代码：

-(void)createDatabase
{
    NSString *libraryPath = [NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES) lastObject];
    NSString *targetPath = [libraryPath stringByAppendingPathComponent:@"gre.db"];


    if (![[NSFileManager defaultManager] fileExistsAtPath:targetPath]) {
        // database doesn't exist in your library path... copy it from the bundle
        NSString *sourcePath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"gre.db"];
        NSError *error = nil;

        if (![[NSFileManager defaultManager] copyItemAtPath:sourcePath toPath:targetPath error:&error]) {
            NSLog(@"Error: %@", error);
        }
    }
}

我从我的 applicationDidFinishLaunchLaunchingWithOptions 调用它并复制数据库

这是我读取数据库的查询：

-(void)readDatabase
{
    wordlist = [[NSMutableArray alloc] init];
    NSString *query =[NSString stringWithFormat:@"SELECT word FROM words WHERE word LIKE '%@%%'",selectedWord]; 
    sqlite3_stmt *statement;
    if (sqlite3_prepare_v2(database, [query UTF8String],-1, &statement, nil) == SQLITE_OK)
    {
        while (sqlite3_step(statement) == SQLITE_ROW)
        {
            char *id1 = (char *)sqlite3_column_text(statement, 0);
            [wordlist addObject:[NSString stringWithFormat:@"%s",id1]];
        }
    }
    sqlite3_finalize(statement);

    NSLog(@"%@",wordlist);

}

现在控件不进入*while (sqlite3_step(statement) == SQLITE_ROW)*循环因此不显示数据。

score 0 · Accepted Answer

使用此代码并在从中获取数据之前检查数据库是否已连接并正确打开。

-(void)readDatabase
    {
        // Set path 
        NSArray *dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);//(customize the path based on your database location)

        NSString *docsDir = [dirPaths objectAtIndex:0];

        NSString *databasePath = [[NSString alloc] initWithString: [docsDir stringByAppendingPathComponent: @"database.db"]];
     const char *dbpath = [databasePath UTF8String]; 


         //Checking connection 
         if (sqlite3_open(dbpath, &SQLitedatabase) == SQLITE_OK)
               {
                 wordlist = [[NSMutableArray alloc] init];
                 NSString *query =[NSString stringWithFormat:@"SELECT word FROM words WHERE word LIKE '%@%%'",selectedWord];
                 sqlite3_stmt *statement;
                 if (sqlite3_prepare_v2(database, [query UTF8String],-1, &statement, nil) == SQLITE_OK)
                 {
                 while (sqlite3_step(statement) == SQLITE_ROW)
                 {
                 char *id1 = (char *)sqlite3_column_text(statement, 0);
                 [wordlist addObject:[NSString stringWithFormat:@"%s",id1]];
                 }
                 }
                 sqlite3_finalize(statement);

                 }
              }  
    }

并确保数据库的初始化也是这样的：

#import <sqlite3.h>

NSString *databasePath;

sqlite3 *SQLiteDataBaseDB;

@implementation DatabaseManager
+(void)initializeDb 
{
    NSString *docsDir;
    NSArray *dirPaths;

    dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

    docsDir = [dirPaths objectAtIndex:0];

    databasePath = [[NSString alloc] initWithString: [docsDir stringByAppendingPathComponent: @"database.db"]];

    NSFileManager *filemgr = [NSFileManager defaultManager];

    if ([filemgr fileExistsAtPath: databasePath ] == NO)
    {
        const char *dbpath = [databasePath UTF8String];

        if (sqlite3_open(dbpath, &SQLiteDataBaseDB) == SQLITE_OK)
        {
            char *errMsg;
            //SELECT name FROM sqlite_master WHERE name=USER_VIDEO_INFO

            const char *sql_stmt = "CREATE TABLE IF NOT EXISTS USER_VIDEO_INFO (userIdentifier TEXT, managerName TEXT, videoPath TEXT, videoName TEXT, shotDate TEXT, session TEXT, videoCategory TEXT)";

            if (sqlite3_exec(SQLiteDataBaseDB, sql_stmt, NULL, NULL, &errMsg) != SQLITE_OK)
            {
                NSLog(@"Failed to create table");
            }

            sqlite3_close(SQLiteDataBaseDB);

        } 
        else
        {
            NSLog(@"Failed to open/create database");
        }

           }

}

并实际检查数据库是否像这样创建...

在此处输入图像描述

score 0 · Accepted Answer

如果您的数据库文件位于资源目录中，请尝试以下代码：

-(NSString*)databasePath
{
   NSString *dbPath = [[NSBundle mainBundle] pathForResource:"gre" forType:"db"];
   return dbPath;
}

实际上，您正在为数据库获取错误的路径。

score 0 · Accepted Answer

您可以测试以下代码。这对我来说可以。

if (userDB == NULL) {
        sqlite3 *newDBconnection;

        NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
        NSString *documentsDirectory = [paths objectAtIndex:0];
        NSString *path = [documentsDirectory stringByAppendingPathComponent:@"gre.sqlite"];

        // Check if the SQL database has already been saved to the users phone, if not then copy it over
        BOOL success;

        // Create a FileManager object, we will use this to check the status
        // of the database and to copy it over if required
        NSFileManager *fileManager = [NSFileManager defaultManager];

        // Check if the database has already been created in the users filesystem
        success = [fileManager fileExistsAtPath:path];

        // If the database already exists then dont do anything
        if(!success)
        {
            NSLog(@"not success");
            // If not then proceed to copy the database from the application to the users filesystem

            // Get the path to the database in the application package
            NSString *databasePathFromApp = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"pero1.sqlite"];

            // Copy the database from the package to the users filesystem
            [fileManager copyItemAtPath:databasePathFromApp toPath:path error:nil];

        }
        NSLog(@"success");

        if (sqlite3_open([path UTF8String], &newDBconnection) == SQLITE_OK) {   
            //NSLog(@"Database Successfully Opened :)");
            userDB = newDBconnection;
        } else {
            NSLog(@"Error in opening database :(");
            userDB = NULL;
    return;
        }
    }
    wordlist = [[NSMutableArray alloc] init];

NSString *query = [NSString stringWithFormat:@"SELECT word FROM words WHERE word LIKE '%@%%'",selectedWord];
        NSLog(@"query: %@",query);

        const char *sqlStatement = [query UTF8String];
        sqlite3_stmt *compiledStatement;
    NSString *listFromDB = @"";
        if(sqlite3_prepare_v2(userDB, sqlStatement, -1, &compiledStatement, NULL) == SQLITE_OK) 
        {
            // Loop through the results and add them to the feeds array
            while(sqlite3_step(compiledStatement) == SQLITE_ROW) {
                // Read the data from the result row
                char *id1 = (char *)sqlite3_column_text(statement, 0);
            [wordlist addObject:[NSString stringWithFormat:@"%s",id1]];

                }
        }
        // Release the compiled statement from memory
        sqlite3_finalize(compiledStatement);

score 0 · Accepted Answer

Ganapathy 你的代码工作得很好！但不是在每次选择查询之前打开数据库，

我在我的代码中尝试了这个，它就像一个魅力！

-(void)createDatabase
{
    NSString *libraryPath = [NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES) lastObject];
    NSString *targetPath = [libraryPath stringByAppendingPathComponent:@"gre.db"];


    if (![[NSFileManager defaultManager] fileExistsAtPath:targetPath]) {
        // database doesn't exist in your library path... copy it from the bundle
        NSString *sourcePath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"gre.db"];
        NSError *error = nil;

        if (![[NSFileManager defaultManager] copyItemAtPath:sourcePath toPath:targetPath error:&error]) {
            NSLog(@"Error: %@", error);
        }
    }

    //Open Database
    if (sqlite3_open([targetPath UTF8String], &database) != SQLITE_OK)
    {
        sqlite3_close(database);
        NSLog(@"Failed to open db.");
    }

}

iphone - 我无法读取我预先存在的 sqlite 数据库

4 回答 4

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