在Sqlite数据库插入和读取图片数据

最新推荐文章于 2021-02-26 16:31:45 发布

最新推荐文章于 2021-02-26 16:31:45 发布 · 874 阅读

文章标签：

#数据库 #人工智能 #移动开发

本文介绍了如何在iOS应用中利用SQLite数据库存储和检索图片。首先将图片转换为NSData格式，接着通过SQL语句插入数据库，并展示了从数据库读取图片并显示的方法。

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在iOS下用sqlite数据库存储图片，先把你的图片转换成 NSData 形式，然后在数据库添加一行 blob 数据

假定数据库中存在表 test_table(name,image), 下面代码将图片文件test.png的二进制数据写到sqlite数据库：

例1

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CHAR*name="test";
NSString*nameString=[NSString stringWithCString:name encoding:NSUTF8StringEncoding];
NSString*filePath=[[NSBundle mainBundle]pathForResource:nameString ofType:@"png"];
IF([[NSFileManager defaultManager]fileExistsAtPath:filePath])
{
NSData*imgData=UIImagePNGRepresentation([UIImage imageWithContentsOfFile:filePath]);
const CHAR*sequel="insert into test_table(name,image) values(?,?)";

sqlite3_stmt*UPDATE;
IF(sqlite3_prepare_v2(DATABASE,sequel,-1,&UPDATE,NULL)==SQLITE_OK)
{
sqlite3_bind_text(UPDATE,1,name,-1,NULL);
sqlite3_bind_blob(UPDATE,2,[imgData bytes],[imgDataLENGTH],NULL);
IF(sqlite3_step(UPDATE)==SQLITE_DONE)
{
NSLog(@"已经写入数据");
}
sqlite3_finalize(UPDATE);
}
}
ELSE
{
NSLog(@"文件不存在");
}

下面代码从数据库中读取图片二进制数据，然后显示图片：
constCHAR*sequel="select image from test_table where name=?";
sqlite3_stmt*getimg;
IF(sqlite3_prepare_v2(DATABASE,sequel,-1,&getimg,NULL)==SQLITE_OK)
{
CHAR*name="test";
sqlite3_bind_text(UPDATE,1,name,-1,NULL);
IF(sqlite3_step(getimg)==SQLITE_ROW)
{
INTbytes=sqlite3_column_bytes(getimg,0);
Byte*VALUE=(Byte*)sqlite3_column_blob(getimg,1);
IF(bytes !=0&&VALUE!=NULL)
{
NSData*DATA=[NSData dataWithBytes:VALUELENGTH:bytes];
UIImage*img=[UIImage imageWithData:DATA];
UIImageView*aview=[[UIImageView alloc]initWithFrame:
                                    CGRectMake(0.0,0.0,IMAGE_WIDTH,IMAGE_HEIGHT)];
aview.image=img;
[SELF.VIEWaddSubview:aview];
[aview release];
}
}
sqlite3_finalize(getimg);
}

例2:存储图片

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// Save Small Image Data by given main url
-(void)SaveImagesToSql:(NSData*)imgData:(NSString*)mainUrl
{
NSLog(@"\n*****Save image to SQLite*****\n");

constchar*sqliteQuery="INSERT INTO IMAGES (URL, IMAGE) VALUES (?, ?)";
sqlite3_stmt*statement;

if(sqlite3_prepare_v2(articlesDB, sqliteQuery,-1,&statement,NULL)==SQLITE_OK)
{
sqlite3_bind_text(statement,1,[mainUrl UTF8String],-1, SQLITE_TRANSIENT);
sqlite3_bind_blob(statement,2,[imgData bytes],[imgData length], SQLITE_TRANSIENT);
sqlite3_step(statement);
}
elseNSLog(@"SaveBody: Failed from sqlite3_prepare_v2. Error is: %s", sqlite3_errmsg(articlesDB));

// Finalize and close database.
sqlite3_finalize(statement);
}

读取图片:

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// Load images from data base with given image url
-(NSData*)LoadImagesFromSql:(NSString*)imageLink
{
NSData*data=nil;
NSString*sqliteQuery=[NSStringstringWithFormat:@"SELECT IMAGE FROM IMAGES WHERE URL = '%@'", imageLink];
sqlite3_stmt*statement;

if(sqlite3_prepare_v2(articlesDB,[sqliteQuery UTF8String],-1,&statement,NULL)==SQLITE_OK)
{
if(sqlite3_step(statement)==SQLITE_ROW)
{
intlength=sqlite3_column_bytes(statement,0);
data =[NSDatadataWithBytes:sqlite3_column_blob(statement,0)length:length];
}
}

// Finalize and close database.
sqlite3_finalize(statement);

returndata;

}