自己看了下MBProgressHUD的源码实现，由于自己用过MBProgressHUD知道里面的UI子控件。所以记录的点因各人而异。
1.打开.m文件看
发现源码的逻辑还是很清晰的，一打开我看到的就是常量的定义，
55012397-0F71-4560-8898-00E661CCB9F0.png
当时看到这里很疑惑1与2方式不是都是常量么，能有什么不一样呢？到后来全局一搜MBProgressMaxOffset，在MBProgressHUD.h中定义了
extern CGFloat const MBProgressMaxOffset;才懂得1是定义了一个外部文件可访问的常量。自己还扩展了
static const 与 #define的区别
相同点：都不能再被修改;一次在定义的地方改了，就全被修改了。
不同点：static const修饰变量只有一份内存。宏定义只是简单的替换；宏可以定义一些方法，运用更加灵活，而const不行。
使用static const修饰更加高效，以后在文件定义常量的地方少写宏。（嘻嘻~）
核心用的方法
+ (instancetype)showHUDAddedTo:(UIView *)view animated:(BOOL)animated;
/// @name Showing and hiding
+ (BOOL)hideHUDForView:(UIView *)view animated:(BOOL)animated;
+ (nullable MBProgressHUD *)HUDForView:(UIView *)view;
2.找到初使化方法入口
有3个初使化方法如下：
- (instancetype)initWithFrame:(CGRect)frame
- (instancetype)initWithCoder:(NSCoder *)aDecoder
- (id)initWithView:(UIView *)view
调用默认配置
- (void)commonInit {
// Set default values for properties
_animationType = MBProgressHUDAnimationFade;
_mode = MBProgressHUDModeIndeterminate;
_margin = 20.0f;
_opacity = 1.f;
_defaultMotionEffectsEnabled = YES;
// Default color, depending on the current iOS version
BOOL isLegacy = kCFCoreFoundationVersionNumber < kCFCoreFoundationVersionNumber_iOS_7_0;
_contentColor = isLegacy ? [UIColor whiteColor] : [UIColor colorWithWhite:0.f alpha:0.7f];
// Transparent background
self.opaque = NO;
self.backgroundColor = [UIColor clearColor];
// Make it invisible for now
self.alpha = 0.0f;
self.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
self.layer.allowsGroupOpacity = NO;
[self setupViews];
[self updateIndicators];
[self registerForNotifications];
}
3.UI布局
- (void)setupViews {
UIColor *defaultColor = self.contentColor;
MBBackgroundView *backgroundView = [[MBBackgroundView alloc] initWithFrame:self.bounds];
backgroundView.style = MBProgressHUDBackgroundStyleSolidColor;
backgroundView.backgroundColor = [UIColor clearColor];
backgroundView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
backgroundView.alpha = 0.f;
[self addSubview:backgroundView];
_backgroundView = backgroundView;
MBBackgroundView *bezelView = [MBBackgroundView new];
bezelView.translatesAutoresizingMaskIntoConstraints = NO;
bezelView.layer.cornerRadius = 5.f;
bezelView.alpha = 0.f;
[self addSubview:bezelView];
_bezelView = bezelView;
[self updateBezelMotionEffects];
UILabel *label = [UILabel new];
label.adjustsFontSizeToFitWidth = NO;
label.textAlignment = NSTextAlignmentCenter;
label.textColor = defaultColor;
label.font = [UIFont boldSystemFontOfSize:MBDefaultLabelFontSize];
label.opaque = NO;
label.backgroundColor = [UIColor clearColor];
_label = label;
UILabel *detailsLabel = [UILabel new];
detailsLabel.adjustsFontSizeToFitWidth = NO;
detailsLabel.textAlignment = NSTextAlignmentCenter;
detailsLabel.textColor = defaultColor;
detailsLabel.numberOfLines = 0;
detailsLabel.font = [UIFont boldSystemFontOfSize:MBDefaultDetailsLabelFontSize];
detailsLabel.opaque = NO;
detailsLabel.backgroundColor = [UIColor clearColor];
_detailsLabel = detailsLabel;
UIButton *button = [MBProgressHUDRoundedButton buttonWithType:UIButtonTypeCustom];
button.titleLabel.textAlignment = NSTextAlignmentCenter;
button.titleLabel.font = [UIFont boldSystemFontOfSize:MBDefaultDetailsLabelFontSize];
[button setTitleColor:defaultColor forState:UIControlStateNormal];
_button = button;
//设置Autolayout优先级
for (UIView *view in @[label, detailsLabel, button]) {
view.translatesAutoresizingMaskIntoConstraints = NO;
[view setContentCompressionResistancePriority:998.f forAxis:UILayoutConstraintAxisHorizontal];
[view setContentCompressionResistancePriority:998.f forAxis:UILayoutConstraintAxisVertical];
[bezelView addSubview:view];
}
UIView *topSpacer = [UIView new];
topSpacer.translatesAutoresizingMaskIntoConstraints = NO;
topSpacer.hidden = YES;
[bezelView addSubview:topSpacer];
_topSpacer = topSpacer;
UIView *bottomSpacer = [UIView new];
bottomSpacer.translatesAutoresizingMaskIntoConstraints = NO;
bottomSpacer.hidden = YES;
[bezelView addSubview:bottomSpacer];
_bottomSpacer = bottomSpacer;
}
然后根据 不同mode的类型相应的设置indicator的视图样式
- (void)updateIndicators
- (void)updateIndicators {
…………
indicator.translatesAutoresizingMaskIntoConstraints = NO;
self.indicator = indicator;
if ([indicator respondsToSelector:@selector(setProgress:)]) {
[(id)indicator setValue:@(self.progress) forKey:@"progress"];
}
//设置视图约束优先级
[indicator setContentCompressionResistancePriority:998.f forAxis:UILayoutConstraintAxisHorizontal];
[indicator setContentCompressionResistancePriority:998.f forAxis:UILayoutConstraintAxisVertical];
[self updateViewsForColor:self.contentColor];//统一设置颜色
[self setNeedsUpdateConstraints];
}
布局重要的部分
约束更新
#pragma mark - Layout
- (void)updateConstraints {
UIView *bezel = self.bezelView; //主要显示的view
UIView *topSpacer = self.topSpacer;
UIView *bottomSpacer = self.bottomSpacer;
CGFloat margin = self.margin;
NSMutableArray *bezelConstraints = [NSMutableArray array];
NSDictionary *metrics = @{@"margin": @(margin)};
//所有view的集合
NSMutableArray *subviews = [NSMutableArray arrayWithObjects:self.topSpacer, self.label, self.detailsLabel, self.button, self.bottomSpacer, nil];
if (self.indicator) [subviews insertObject:self.indicator atIndex:1];
// Remove existing constraints 移除所有存在的约束
[self removeConstraints:self.constraints];
[topSpacer removeConstraints:topSpacer.constraints];
[bottomSpacer removeConstraints:bottomSpacer.constraints];
if (self.bezelConstraints) {
[bezel removeConstraints:self.bezelConstraints];
self.bezelConstraints = nil;
}
// Center bezel in container (self), applying the offset if set
//bezel居中约束，如果设置了offset，就偏移offset
CGPoint offset = self.offset;
NSMutableArray *centeringConstraints = [NSMutableArray array];
[centeringConstraints addObject:[NSLayoutConstraint constraintWithItem:bezel attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeCenterX multiplier:1.f constant:offset.x]];
[centeringConstraints addObject:[NSLayoutConstraint constraintWithItem:bezel attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeCenterY multiplier:1.f constant:offset.y]];
[self applyPriority:998.f toConstraints:centeringConstraints];
[self addConstraints:centeringConstraints];
// Ensure minimum side margin is kept
NSMutableArray *sideConstraints = [NSMutableArray array];
[sideConstraints addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"|-(>=margin)-[bezel]-(>=margin)-|" options:0 metrics:metrics views:NSDictionaryOfVariableBindings(bezel)]];//约束的另一种表现形式，VFL语法
[sideConstraints addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-(>=margin)-[bezel]-(>=margin)-|" options:0 metrics:metrics views:NSDictionaryOfVariableBindings(bezel)]];
[self applyPriority:999.f toConstraints:sideConstraints];
[self addConstraints:sideConstraints];
// Minimum bezel size, if set
CGSize minimumSize = self.minSize;
if (!CGSizeEqualToSize(minimumSize, CGSizeZero)) {
NSMutableArray *minSizeConstraints = [NSMutableArray array];
[minSizeConstraints addObject:[NSLayoutConstraint constraintWithItem:bezel attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationGreaterThanOrEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.f constant:minimumSize.width]];
[minSizeConstraints addObject:[NSLayoutConstraint constraintWithItem:bezel attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationGreaterThanOrEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.f constant:minimumSize.height]];
[self applyPriority:997.f toConstraints:minSizeConstraints];
[bezelConstraints addObjectsFromArray:minSizeConstraints];
}
// Square aspect ratio, if set
if (self.square) {
NSLayoutConstraint *square = [NSLayoutConstraint constraintWithItem:bezel attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:bezel attribute:NSLayoutAttributeWidth multiplier:1.f constant:0];
square.priority = 997.f;
[bezelConstraints addObject:square];
}
// Top and bottom spacing
[topSpacer addConstraint:[NSLayoutConstraint constraintWithItem:topSpacer attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationGreaterThanOrEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.f constant:margin]];
[bottomSpacer addConstraint:[NSLayoutConstraint constraintWithItem:bottomSpacer attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationGreaterThanOrEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.f constant:margin]];
// Top and bottom spaces should be equal
[bezelConstraints addObject:[NSLayoutConstraint constraintWithItem:topSpacer attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:bottomSpacer attribute:NSLayoutAttributeHeight multiplier:1.f constant:0.f]];
// Layout subviews in bezel
//subViews主要有这些子控件 self.topSpacer, self.label, self.detailsLabel, self.button, self.bottomSpacer,
//如果有self.indicator，那这个数组就是这样的顺序 self.topSpacer, self.indicator,self.label, self.detailsLabel, self.button, self.bottomSpacer,
NSMutableArray *paddingConstraints = [NSMutableArray new];
[subviews enumerateObjectsUsingBlock:^(UIView *view, NSUInteger idx, BOOL *stop) {
// Center in bezel
[bezelConstraints addObject:[NSLayoutConstraint constraintWithItem:view attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:bezel attribute:NSLayoutAttributeCenterX multiplier:1.f constant:0.f]];
// Ensure the minimum edge margin is kept
[bezelConstraints addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"|-(>=margin)-[view]-(>=margin)-|" options:0 metrics:metrics views:NSDictionaryOfVariableBindings(view)]];
// Element spacing
if (idx == 0) {
// First, ensure spacing to bezel edge
[bezelConstraints addObject:[NSLayoutConstraint constraintWithItem:view attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:bezel attribute:NSLayoutAttributeTop multiplier:1.f constant:0.f]];
} else if (idx == subviews.count - 1) {
// Last, ensure spacing to bezel edge
[bezelConstraints addObject:[NSLayoutConstraint constraintWithItem:view attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual toItem:bezel attribute:NSLayoutAttributeBottom multiplier:1.f constant:0.f]];
}
if (idx > 0) {
// Has previous
NSLayoutConstraint *padding = [NSLayoutConstraint constraintWithItem:view attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:subviews[idx - 1] attribute:NSLayoutAttributeBottom multiplier:1.f constant:0.f];
[bezelConstraints addObject:padding];
[paddingConstraints addObject:padding];
}
}];
[bezel addConstraints:bezelConstraints];
self.bezelConstraints = bezelConstraints;
self.paddingConstraints = [paddingConstraints copy];
[self updatePaddingConstraints];
[super updateConstraints];
}
- (void)layoutSubviews {
// There is no need to update constraints if they are going to
// be recreated in [super layoutSubviews] due to needsUpdateConstraints being set.
// This also avoids an issue on iOS 8, where updatePaddingConstraints
// would trigger a zombie object access.
if (!self.needsUpdateConstraints) {
[self updatePaddingConstraints];
}
[super layoutSubviews];
}
4. CADisplayLink的运用
CADisplayLink是一个能让我们以和频率刷新率同步的频率将特定的内容画到屏幕上的定时器类。CADisplayLink以特定模式注册到runloop后，每当屏幕刷新结束的时候，runloop就会向CADisplayLink指定的target发送一次指定的selector消息， CADisplayLink类对应的selector就会被调用一次。
在设置progress进度条进度时，作者是采用CADisplayLink 来定时刷新的
#pragma mark - NSProgress
- (void)setNSProgressDisplayLinkEnabled:(BOOL)enabled {
// We're using CADisplayLink, because NSProgress can change very quickly and observing it may starve the main thread,
// so we're refreshing the progress only every frame draw
if (enabled && self.progressObject) {
// Only create if not already active.
if (!self.progressObjectDisplayLink) {
self.progressObjectDisplayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(updateProgressFromProgressObject)];
}
} else {
self.progressObjectDisplayLink = nil;
}
}
- (void)updateProgressFromProgressObject {
self.progress = self.progressObject.fractionCompleted;
}
3个timer的运用
@property (nonatomic, weak) NSTimer *graceTimer;
@property (nonatomic, weak) NSTimer *minShowTimer;
@property (nonatomic, weak) NSTimer *hideDelayTimer;
graceTimer: 在源码中如果设置了graceTime（默认是0的），它会推迟将要显示的HUD动画，graceTime时间到了它才会执行HUD动画。设置这个graceTime主要是避免HUD显示时间太短,造成一闪而过的差体验。
/*
* Grace period is the time (in seconds) that the invoked method may be run without
* showing the HUD. If the task finishes before the grace time runs out, the HUD will
* not be shown at all.
* This may be used to prevent HUD display for very short tasks.
* Defaults to 0 (no grace time).
*/
@property (assign, nonatomic) NSTimeInterval graceTime;
#pragma mark - Show & hide
- (void)showAnimated:(BOOL)animated {
MBMainThreadAssert();
[self.minShowTimer invalidate];
self.useAnimation = animated;
self.finished = NO;
// If the grace time is set, postpone the HUD display
if (self.graceTime > 0.0) {
NSTimer *timer = [NSTimer timerWithTimeInterval:self.graceTime target:self selector:@selector(handleGraceTimer:) userInfo:nil repeats:NO];
[[NSRunLoop currentRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];
self.graceTimer = timer;
}
// ... otherwise show the HUD immediately
else {
[self showUsingAnimation:self.useAnimation];
}
}
#pragma mark - Timer callbacks
- (void)handleGraceTimer:(NSTimer *)theTimer {
// Show the HUD only if the task is still running
if (!self.hasFinished) {
[self showUsingAnimation:self.useAnimation];
}
}
minShowTimer：从源码中可以看出来，如果设定了minShowTime，就会在-hideAnimated:(BOOL)animated方法触发后判断任务执行的时间是否短于minShowTime。即使任务在minShowTime之前完成了，HUD也不会立即消失，它会在走完minShowTime之后才消失，这也是一种提升体验的操作。
- (void)hideAnimated:(BOOL)animated {
MBMainThreadAssert();
[self.graceTimer invalidate];
self.useAnimation = animated;
self.finished = YES;
// If the minShow time is set, calculate how long the HUD was shown,
// and postpone the hiding operation if necessary
if (self.minShowTime > 0.0 && self.showStarted) {
NSTimeInterval interv = [[NSDate date] timeIntervalSinceDate:self.showStarted];
if (interv < self.minShowTime) {
NSTimer *timer = [NSTimer timerWithTimeInterval:(self.minShowTime - interv) target:self selector:@selector(handleMinShowTimer:) userInfo:nil repeats:NO];
[[NSRunLoop currentRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];
self.minShowTimer = timer;
return;
}
}
// ... otherwise hide the HUD immediately
[self hideUsingAnimation:self.useAnimation];
}
hideDelayTimer：用来推迟HUD的隐藏。具体分析可以看源码
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