hOW 从 URL 设置图像而不眨眼

Question

我正在从ImagePicker上传图像，一旦图像上传到服务器上，我就会从URL显示它。所以从本地图像到URL图像，有一个眨眼，我想避免，但我无法修复它。

我正在添加下面的代码：

- (void)setDataOnCell:(NSDictionary *)dict {
self.messageTimeLabel.text = [CommonUtils checkForNUllValue:[dict valueForKey:@"msg_time"]];
if (![[CommonUtils checkForNUllValue:[dict valueForKey:@"msg_status"]] isEqualToString:@"Read"]) {
self.messageTickImageView.image = [UIImage imageNamed:@"check_delivered_icon"];
self.messageStatusLabel.textColor = [UIColor colorWithRed:166.0f/255.0f green:166.0f/255.0f blue:166.0f/255.0f alpha:1.0];
}
else {
self.messageTickImageView.image = [UIImage imageNamed:@"check_read_icon"];
self.messageStatusLabel.textColor = [UIColor colorWithRed:254.0f/255.0f green:223.0f/255.0f blue:224.0f/255.0f alpha:1.0];
}
self.messageStatusLabel.text = [CommonUtils checkForNUllValue:[dict valueForKey:@"msg_status"]];

if ([[NSString stringWithFormat:@"%@", [dict valueForKey:@"attachment_type"]] isEqualToString:@"local_img"]){
self.messageImageview.image = [dict valueForKey:@"attachment"];
}
else {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0),
^{
NSURL *imageURL = [NSURL URLWithString:[NSString stringWithFormat:@"%@", [NSString stringWithFormat:@"%@", [dict valueForKey:@"attachment"]]]];
NSData *urlData = [NSData dataWithContentsOfURL:imageURL];
//This is your completion handler
dispatch_sync(dispatch_get_main_queue(), ^{
UIImage *image = [UIImage imageWithData:urlData];
self.messageImageview.image = image;
});
});


}
}

Answer 1

首先，您需要在此图像视图上设置默认图像，然后通过URL调用图像并在此上进行设置

NSOperationQueue *queueThumbnl = [[NSOperationQueue alloc] init];
[queueThumbnl setMaxConcurrentOperationCount:NSOperationQueueDefaultMaxConcurrentOperationCount];
[queueThumbnl addOperationWithBlock:^{
// Background work
NSURL *imageURL = [NSURL URLWithString:[NSString stringWithFormat:@"%@", [NSString stringWithFormat:@"%@", [dict valueForKey:@"attachment"]]]];
NSData *urlData = [NSData dataWithContentsOfURL:imageURL];
UIImage *image = [UIImage imageWithData:urlData];
NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:self.messageImageview, @"messageImageview", urlData, @"imageData", nil];
[self performSelectorOnMainThread:@selector(mainThreadUIUpdate:) withObject:dict waitUntilDone:YES];
//  [self updateThumbnailOnMainThread:anItem setImageTo:cell];
}];

-(void)mainThreadUIUpdate:(NSDictionary *)dict
{
UIImageView *messge = [dict objectForKey:@"messageImageview"];
UIImage *image = [dict objectForKey:@"image"];
[messge.imageView setImage:image];
[cell.imageView setNeedsDisplay:YES];
}