关于iPhone-从文件夹中显示图片

显示保存在文件夹中的图片。只返回了文件名字，没显示。

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
            NSString *documentsDirectory = [paths objectAtIndex:0];  
            NSString*patientlastName;    
            NSString*test=@"nicej";
           patientlastName=[test stringByReplacingOccurrencesOfString:@" " withString:@""];
        NSString * filePath = [NSString stringWithFormat:@"%@/Documents//%@.png", NSHomeDirectory(),patientlastName];
        BOOL fileExists = [[NSFileManager defaultManager] fileExistsAtPath:filePath];
        if (fileExists == 0) 
        { 
            NSLog(@"File is Not exists");
            appDelegate.imageURL=@"File Not Exists";
        }
        NSString *userfile=[NSString stringWithFormat:@"%@",patientlastName];
        appDelegate.imageURL=userfile;

           PictureDisplayViewController *targetController = [[PictureDisplayViewController alloc] initWithNibName:@"PictureDisplayViewController" bundle:nil];
        targetController.modalPresentationStyle = UIModalPresentationFullScreen;
        [self.splitViewController presentViewController:targetController animated:YES completion:nil];


PictureDisplayViewController中：
       imageView.image=[UIImage imageNamed:@"nicej.png"];