开发过程中遇到的一些小问题。
这两天做滤镜的代码，总是会概率性出现全局动画失效的情况。stackOverFlow 和 cocoaChina搜索了一下，得出结论可能是非主线程调用UI所致。仔细检查了一遍代码，并没有在非主线程调用UI,注释加断点，最后发现是在非主线程对image设置了滤镜所致。代码如下：
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0);
dispatch_queue_t syncqueue = dispatch_queue_create("com.snapsliderfilters.app",nil);
dispatch_apply(filters.count, queue, ^(size_t index){
SNFilter *filterComputed = [originalImage applyFilter:filters[index]];
dispatch_sync(syncqueue, ^{
[finalFilters addObject:filterComputed];
return;
});});
- (SNFilter*)applyFilter:(NSString*)filterName
{
SNFilter*filter = [selfcopy];
filter.name= filterName;
if(![self.filterNameListcontainsObject:filterName]) {
NSLog(@"这个滤镜不存在");
returnfilter;
}elseif([filterNameisEqualToString:@"No Filter"]) {
returnfilter;
}else{
CIImage*sourceImage = [[CIImagealloc]initWithCGImage:filter.image.CGImageoptions:nil];
CIFilter*myFilter = [CIFilterfilterWithName:filterName];
[myFiltersetDefaults];
[myFiltersetValue:sourceImageforKey:kCIInputImageKey];
CIContext*context = [CIContextcontextWithOptions:nil];
CGImageRefoutputCGImage = [contextcreateCGImage:myFilter.outputImagefromRect:myFilter.outputImage.extent];
UIImage* filteredImage = [UIImageimageWithCGImage:outputCGImage];
filter.image= filteredImage;
returnfilter;
}
returnnil;
}
其实这些ui并没有显示在屏幕上。因此渲染UI一定要在主线程不止是指显示在屏幕上的，也指ui的离屏处理。（会不会是线程安全问题？线程不安全最多造成数据错乱，而不应该是动画失效。也不很确定，对苹果底层动画渲染机制了解的不够多。）
处理方法：简单粗暴，直接for
for(inti =0; i < filters.count; i++) {
SNFilter*filterComputed = [originalImageapplyFilter:filters[i]];
[finalFiltersaddObject:filterComputed];
}