效果图
@property (weak,nonatomic)IBOutletUILabel *downLabelInfo;
@property (weak,nonatomic)IBOutletUIImageView *imageView;
@end
@implementationViewController
- (void)viewDidLoad
{
[super viewDidLoad];
NSString *url =@"http://d.hiphotos.baidu.com/image/w%3D1366%3Bcrop%3D0%2C0%2C1366%2C768/sign=6cbcab9dabec8a13141a53e3c135aaec/aa64034f78f0f7369453c3730855b319ebc41316.jpg";
@autoreleasepool {
NSThread *thread = [[NSThreadalloc]initWithTarget:selfselector:@selector(downloadImage:)object:url];
[thread start];
}
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
}
-(void) downloadImage:(NSString *)url {
// 要把显示的内容放到同步方法前面即可
self->_downLabelInfo.text =@"正在下载图片中...";
// 同步方法 会卡线程直到完成位置
NSData *imageData = [NSDatadataWithContentsOfURL:[NSURLURLWithString:url]];
UIImage *image =[UIImageimageWithData:imageData];
if(image==nil)
{
}
else
{
//self->_downLabelInfo.text = @"正在下载图片中...";所以这条语句写了也没用
[self performSelectorOnMainThread:@selector(updateImageView:)withObject:(image)waitUntilDone:YES];
}
}
-(void) updateImageView:(UIImage *)image
{
self->_imageView.image = image;
self->_imageView.frame=CGRectMake(self.view.frame.size.width/2-100,self.view.frame.size.height/2-100,200, 200);
self->_downLabelInfo.textColor = [UIColorredColor];
self->_downLabelInfo.text =@"图片下载完成";
}
@end
第二种方式使用 NSURLConnection sendSynchronousRequest 同步方式获取图片内容并显示
将downloadImage方法修改如下
-(void) downloadImage:(NSString *)url
{
self->_downLabelInfo.text =@"正在下载图片中...";
NSURLRequest *request = [NSURLRequestrequestWithURL:[NSURLURLWithString:url]];
NSError *error;
// 此处将会造成阻塞
NSData *data = [NSURLConnectionsendSynchronousRequest:requestreturningResponse:nilerror:&error];
if(data ==nil)
{
NSLog(@"nil");
}
else
{
UIImage *image =[UIImageimageWithData:data];
self->_imageView.image = image;
self->_downLabelInfo.textColor = [UIColorredColor];
self->_downLabelInfo.text =@"图片下载完成";
}
}