有时候我们会遇到在同一个页面发起多个网络请求的情况。普遍的做法是采用dispatch_group，当组内的所有方法都完成之后执行reloadData，达到只显示一次加载动画的效果。
先来看看代码:
- (void)viewDidLoad {
[super viewDidLoad];
[self.progressHUD showAnimated:YES];
dispatch_group_t group = dispatch_group_create();
[self request1:group];
[self request2:group];
dispatch_group_notify(group, dispatch_get_main_queue(), ^{
//所有请求完成，结束动画
[self.progressHUD hideAnimated:YES];
});
}
- (void)request1:(dispatch_group_t)group {
dispatch_group_enter(group);
[manager GET:@"https://xxx.json" parameters:@{} progress:^(NSProgress * _Nonnull downloadProgress) {
} success:^(NSURLSessionDataTask * _Nonnull task, id _Nullable responseObject) {
dispatch_group_leave(group);
} failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
dispatch_group_leave(group);
}];
}
- (void)request2:(dispatch_group_t)group {
dispatch_group_enter(group);
[manager GET:@"https://xxx.json" parameters:@{} progress:^(NSProgress * _Nonnull downloadProgress) {
} success:^(NSURLSessionDataTask * _Nonnull task, id _Nullable responseObject) {
dispatch_group_leave(group);
} failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
dispatch_group_leave(group);
}];
}
这种做法，在网络请求不是很多，并且网速良好的情况，用户体验很好，但是当网络请求很多，同时网络差的时候，用户会一直看到MBProgressHUD的等待动画。我们希望，在加载完一个请求之后，展示UI，同时MBProgressHUD的等待动画继续，以此类推，当所有的请求完成之后，结束MBProgressHUD等待动画。
下面是代码演示，代码很粗糙，大家可以根据思想自己去实现。
#import <Foundation/Foundation.h>
#import "MBProgressHUD.h"
@interface IdiotSentinelProgressHUD : NSObject
+ (void)showHUDAddedTo:(UIView *)view animated:(BOOL)animated;
+ (void)showHUDAddedTo:(UIView *)view withCount:(NSInteger)count animated:(BOOL)animated;
+ (void)hideHUDForView:(UIView *)view animated:(BOOL)animated endBlock:(void (^)(NSInteger i))end;
+ (void)finalHideHUDForView:(UIView *)view animated:(BOOL)animated endBlock:(void (^)(NSInteger i))end;
@end
@interface UIView (Sentinel)
/**
设置Sentinel数量
@param i 数
*/
- (void)setSentinel:(NSInteger)i;
/**
获取Sentinel数量
@return Sentinel数量
*/
- (NSInteger)getSentinel;
/**
如果当前展示了HUD 设置为YES 反之NO
@param show BOOL
*/
- (void)setShowHUD:(BOOL)show;
/**
当前是否展示HUD
@return YES正在展示，反之不在展示
*/
- (BOOL)getShowHUD;
@end
#import "IdiotSentinelProgressHUD.h"
#import <objc/runtime.h>
@implementation IdiotSentinelProgressHUD
+ (void)showHUDAddedTo:(UIView *)view animated:(BOOL)animated {
[IdiotSentinelProgressHUD showHUDAddedTo:view withCount:1 animated:animated];
}
+ (void)showHUDAddedTo:(UIView *)view withCount:(NSInteger)count animated:(BOOL)animated {
NSInteger i = [view getSentinel] + count;
[view setSentinel:i];
if ([view getShowHUD]) {
return;
}
if (i > 0) {
[MBProgressHUD showHUDAddedTo:view animated:animated];
[view setShowHUD:YES];
}
}
+ (void)hideHUDForView:(UIView *)view animated:(BOOL)animated endBlock:(void (^)(NSInteger i))end {
NSInteger i = [view getSentinel] - 1;
[view setSentinel:MAX(i,0)];
i = [view getSentinel];
if (i <= 0) {
[MBProgressHUD hideHUDForView:view animated:animated];
[view setShowHUD:NO];
if (end) {
end(i);
}
return;
}
if (end) {
end(i);
}
}
+ (void)finalHideHUDForView:(UIView *)view animated:(BOOL)animated endBlock:(void (^)(NSInteger i))end {
[MBProgressHUD hideHUDForView:view animated:animated];
[view setSentinel:0];
[view setShowHUD:NO];
if (end) {
end(0);
}
}
@end
static NSString *SentinelCount = @"SentinelCount";
static NSString *SentinelShowHUD = @"SentinelShowHUD";
@implementation UIView (Sentinel)
- (void)setSentinel:(NSInteger)i {
@synchronized(self) {
objc_setAssociatedObject(self, &SentinelCount, [NSNumber numberWithInteger:i], OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
}
- (NSInteger)getSentinel {
@synchronized(self) {
NSNumber *i = objc_getAssociatedObject(self, &SentinelCount);
return i==nil?0:[i integerValue];
}
}
- (void)setShowHUD:(BOOL)show {
@synchronized(self) {
objc_setAssociatedObject(self, &SentinelShowHUD, [NSNumber numberWithBool:show], OBJC_ASSOCIATION_ASSIGN);
}
}
- (BOOL)getShowHUD {
@synchronized(self) {
NSNumber *show = objc_getAssociatedObject(self, &SentinelShowHUD);
return show==nil?NO:[show boolValue];
}
}
@end
使用效果:
gif5新文件.gif
