将图片转换成二进制写入sqlite

先看看网上找的例子代码：

写入：

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask,YES);
NSString *dataPath = [[paths objectAtIndex:0] stringByAppendingPathComponent:@”sqlite.sqlite”];

NSData *image=UIImagePNGRepresentation([UIImage imageNamed:@"01_02.png"]);
NSString *aaa=[[NSString alloc]initWithFormat:@”update cards set c_image=? where id=1″];

sqlite3 *database;

if (sqlite3_open([dataPath UTF8String],&database) == SQLITE_OK){
sqlite3_stmt * compliedStatement;
sqlite3_prepare(database,[aaa UTF8String],-1,&compliedStatement,0);
sqlite3_bind_blob(compliedStatement,1,[image bytes],[image length],NULL);
int result=sqlite3_step(compliedStatement);
if (result==SQLITE_DONE) {
}
sqlite3_finalize(compliedStatement);

}
sqlite3_close(database);
[aaa release];

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,YES);
NSString *dataPath = [[paths objectAtIndex:0] stringByAppendingPathComponent:@”sqlite.sqlite”];
sqlite3 *database;
if (sqlite3_open([dataPath UTF8String],&database) == SQLITE_OK){
const char *sqlStatement=”select c_image from cards where id=1″;
sqlite3_stmt *compliedStatement;
if(sqlite3_prepare(database,sqlStatement,NULL)==SQLITE_OK)
{
while (sqlite3_step(compliedStatement)==SQLITE_ROW) {
int bytes = sqlite3_column_bytes(compliedStatement,0);
const void *value = sqlite3_column_blob(compliedStatement,0);
if( value != NULL && bytes != 0 ){
NSData *data = [NSData dataWithBytes:value length:bytes];
UIImage *image=[UIImage imageWithData:data];
[imageView setImage:image];

}
else{

}
}
}
sqlite3_finalize(compliedStatement);
}
sqlite3_close(database);

以上，思路就是：sqlite可以存放二进制的字段（blob），故可将图片转成NSData再写入sqlite。读取则是一个逆向过程。

在这里值得一说的是，自己尝试的时候，数据能写入，但是读出却是null。。搞了一个早上，原来是查询语句写错了。。。要细心啊

（编辑：李大同）

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