描述：
列表没有数据、无网络状态下显示占位图处理
场景：
列表没有数据、无网络状态
原理：
捕捉UITableView/UICollectionView的reloadData事件，判断列表有无数据，处理展示占位图逻辑
介绍：
- EmpySet使用分类UIScrollView+CYEmptySet实现
- 对无任何侵入性，不依赖于任何三方库
使用：
Paste_Image.png
Demo展示：
CYEmptySet.gif
部分代码：
static char CYEmptySetCustomViewKey;
static char CYEmptySetContentViewKey;
static char CYEmptySetEmptyEnabledKey;
@interface UIScrollView ()
@property (nonatomic, weak) UIView *contentView;
@end
@implementation UIScrollView (CYEmptySet)
- (void)exchangeSeletor1:(SEL)selector1 selector2:(SEL)selector2 {
Class class = [self class];
Method originalMethod = class_getInstanceMethod(class, selector1);
Method swizzledMethod = class_getInstanceMethod(class, selector2);
// Change implementation
BOOL success = class_addMethod(class, selector1, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod));
if (success) {
class_replaceMethod(class, selector2, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod));
} else {
method_exchangeImplementations(originalMethod, swizzledMethod);
}
}
- (void)setContentView:(UIView *)contentView {
objc_setAssociatedObject(self, &CYEmptySetContentViewKey, contentView, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
- (UIView *)contentView {
UIView *contentView = objc_getAssociatedObject(self, &CYEmptySetContentViewKey);
if (!contentView) {
contentView = [UIView new];
contentView.backgroundColor = [UIColor clearColor];
self.contentView = contentView;
}
contentView.translatesAutoresizingMaskIntoConstraints = false;
return contentView;
}
- (void)cy_reloadData {
[self cy_reloadData];
if (!self.emptyEnabled) return;
UIView *contentView = self.contentView;
if ([self rowCount] == 0) {
if (([self isKindOfClass:[UITableView class]] || [self isKindOfClass:[UICollectionView class]])
&& !contentView.superview
&& self.subviews.count > 1) {
[self addSubview:contentView];
[self insertSubview:contentView atIndex:0];
if (self.customEmptyView) {
self.customEmptyView.translatesAutoresizingMaskIntoConstraints = false;
[contentView addSubview:self.customEmptyView];
}
[self addConstraint:[NSLayoutConstraint constraintWithItem:self.contentView
attribute:NSLayoutAttributeWidth
relatedBy:NSLayoutRelationEqual
toItem:self
attribute:NSLayoutAttributeWidth
multiplier:1.0
constant:0.0]];
[self addConstraint:[NSLayoutConstraint constraintWithItem:self.contentView
attribute:NSLayoutAttributeHeight
relatedBy:NSLayoutRelationEqual
toItem:self
attribute:NSLayoutAttributeHeight
multiplier:1.0
constant:0.0]];
[self addConstraintWithLayoutAttributes:@[@(NSLayoutAttributeLeft),
@(NSLayoutAttributeBottom),
@(NSLayoutAttributeRight)] view:self.contentView equalToSuperView:self];
[self addConstraint:[NSLayoutConstraint constraintWithItem:self.contentView
attribute:NSLayoutAttributeTop
relatedBy:NSLayoutRelationEqual
toItem:self
attribute:NSLayoutAttributeTop
multiplier:1.0 constant:-self.contentInset.top]];
[self addConstraintWithLayoutAttributes:@[@(NSLayoutAttributeTop),
@(NSLayoutAttributeLeft),
@(NSLayoutAttributeBottom),
@(NSLayoutAttributeRight)] view:self.customEmptyView equalToSuperView:self.contentView];
}
} else {
[contentView.subviews makeObjectsPerformSelector:@selector(removeFromSuperview)];
[contentView removeFromSuperview];
self.contentView = nil;
}
}
- (void)addConstraintWithLayoutAttributes:(NSArray *)attributes view:(UIView *)view equalToSuperView:(UIView *)superView {
if (!superView || !view) return;
for (NSNumber *attribute in attributes) {
NSLayoutAttribute att = attribute.integerValue;
NSLayoutConstraint *constraint = [NSLayoutConstraint constraintWithItem:view
attribute:att
relatedBy:NSLayoutRelationEqual
toItem:superView
attribute:att
multiplier:1.0
constant:0.0];
[superView addConstraint:constraint];
}
}
- (NSInteger)rowCount {
NSInteger rowCount = 0;
if ([self isKindOfClass:[UITableView class]]) {
UITableView *tableView = (UITableView *)self;
for (NSInteger section = 0; section < tableView.numberOfSections; section++) {
rowCount += [tableView numberOfRowsInSection:section];
}
} else if ([self isKindOfClass:[UICollectionView class]]) {
UICollectionView *collectionView = (UICollectionView *)self;
for (NSInteger section = 0; section < collectionView.numberOfSections; section++) {
rowCount += [collectionView numberOfItemsInSection:section];
}
}
return rowCount;
}
- (UIView *)customEmptyView {
return objc_getAssociatedObject(self, &CYEmptySetCustomViewKey);
}
- (void)setCustomEmptyView:(UIView *)customEmptyView {
objc_setAssociatedObject(self, &CYEmptySetCustomViewKey, customEmptyView, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
- (BOOL)emptyEnabled {
return [objc_getAssociatedObject(self, &CYEmptySetEmptyEnabledKey) boolValue];
}
- (void)setEmptyEnabled:(BOOL)emptyEnabled {
if (emptyEnabled) {
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
[self exchangeSeletor1:@selector(reloadData) selector2:@selector(cy_reloadData)];
});
}
objc_setAssociatedObject(self, &CYEmptySetEmptyEnabledKey, @(emptyEnabled), OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}