第三方类MBProcessHUD的阅读和理解

最新推荐文章于 2018-12-25 11:04:01 发布

原创最新推荐文章于 2018-12-25 11:04:01 发布 · 1k 阅读

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本文详细解析了 MBProgressHUD 类中的 KVO (键值观察) 实现方式，包括如何注册和取消 KVO，以及如何根据观察到的属性变化更新 UI。通过分析 updateUIForKeypath 方法，展示了如何根据不同属性的变化进行相应的 UI 更新。

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平常做项目没时间是不会在意一些第三方类的具体实现，稍作了解后便直接用，这两天闲下来，具体看了看MBProcessHUD这个类。下面谈谈看法

MBProcesHUD这个类主要是实现一些消息提醒，具体的比如加载中，加载失败或者其他任何你想的提示！

在这个类的实现中，有一个值得注意的是采用的是键值观察KVO来实现的，比如代码中

#pragma mark - KVO

- (void)registerForKVO {
	for (NSString *keyPath in [self observableKeypaths]) {
		[self addObserver:self forKeyPath:keyPath options:NSKeyValueObservingOptionNew context:NULL];
	}
}

- (void)unregisterFromKVO {
	for (NSString *keyPath in [self observableKeypaths]) {
		[self removeObserver:self forKeyPath:keyPath];
	}
}

- (NSArray *)observableKeypaths {
	return [NSArray arrayWithObjects:@"mode", @"customView", @"labelText", @"labelFont", 
			@"detailsLabelText", @"detailsLabelFont", @"progress", nil];
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
	if (![NSThread isMainThread]) {
		[self performSelectorOnMainThread:@selector(updateUIForKeypath:) withObject:keyPath waitUntilDone:NO];
	} else {
		[self updateUIForKeypath:keyPath];
	}
}

通过如果对象的属性发生了改变，则通过观察者的回调函数，进行UI上面的更改，也即是updateUIForKeypath这个函数

- (void)updateUIForKeypath:(NSString *)keyPath {
	if ([keyPath isEqualToString:@"mode"] || [keyPath isEqualToString:@"customView"]) {
		[self updateIndicators];
	} else if ([keyPath isEqualToString:@"labelText"]) {
		label.text = self.labelText;
	} else if ([keyPath isEqualToString:@"labelFont"]) {
		label.font = self.labelFont;
	} else if ([keyPath isEqualToString:@"detailsLabelText"]) {
		detailsLabel.text = self.detailsLabelText;
	} else if ([keyPath isEqualToString:@"detailsLabelFont"]) {
		detailsLabel.font = self.detailsLabelFont;
	} else if ([keyPath isEqualToString:@"progress"]) {
		if ([indicator respondsToSelector:@selector(setProgress:)]) {
			[(id)indicator setProgress:progress];
		}
		return;
	}
	[self setNeedsLayout];
	[self setNeedsDisplay];
}

而在updateUIForKeypath这个函数中，主要是针对键值变化，最后进行UI上的由[self setNeedsLayout] 和[self setNeedsDisplay]进行重绘。这两个函数分别调用layoutSubviews和drawRect这两个函数UI上重绘

- (void)drawRect:(CGRect)rect {
	
	CGContextRef context = UIGraphicsGetCurrentContext();
	UIGraphicsPushContext(context);

	if (self.dimBackground) {
		//Gradient colours
		size_t gradLocationsNum = 2;
		CGFloat gradLocations[2] = {0.0f, 1.0f};
		CGFloat gradColors[8] = {0.0f,0.0f,0.0f,0.0f,0.0f,0.0f,0.0f,0.75f}; 
		CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
		CGGradientRef gradient = CGGradientCreateWithColorComponents(colorSpace, gradColors, gradLocations, gradLocationsNum);
		CGColorSpaceRelease(colorSpace);
		//Gradient center
		CGPoint gradCenter= CGPointMake(self.bounds.size.width/2, self.bounds.size.height/2);
		//Gradient radius
		float gradRadius = MIN(self.bounds.size.width , self.bounds.size.height) ;
		//Gradient draw
		CGContextDrawRadialGradient (context, gradient, gradCenter,
									 0, gradCenter, gradRadius,
									 kCGGradientDrawsAfterEndLocation);
		CGGradientRelease(gradient);
	}

    // Set background rect color
    if (self.color) {
        CGContextSetFillColorWithColor(context, self.color.CGColor);
    } else {
        CGContextSetGrayFillColor(context, 0.0f, self.opacity);
    }

	
	// Center HUD
	CGRect allRect = self.bounds;
	// Draw rounded HUD backgroud rect
	CGRect boxRect = CGRectMake(roundf((allRect.size.width - size.width) / 2) + self.xOffset,
								roundf((allRect.size.height - size.height) / 2) + self.yOffset, size.width, size.height);
	float radius = 10.0f;
	CGContextBeginPath(context);
	CGContextMoveToPoint(context, CGRectGetMinX(boxRect) + radius, CGRectGetMinY(boxRect));
	CGContextAddArc(context, CGRectGetMaxX(boxRect) - radius, CGRectGetMinY(boxRect) + radius, radius, 3 * (float)M_PI / 2, 0, 0);
	CGContextAddArc(context, CGRectGetMaxX(boxRect) - radius, CGRectGetMaxY(boxRect) - radius, radius, 0, (float)M_PI / 2, 0);
	CGContextAddArc(context, CGRectGetMinX(boxRect) + radius, CGRectGetMaxY(boxRect) - radius, radius, (float)M_PI / 2, (float)M_PI, 0);
	CGContextAddArc(context, CGRectGetMinX(boxRect) + radius, CGRectGetMinY(boxRect) + radius, radius, (float)M_PI, 3 * (float)M_PI / 2, 0);
	CGContextClosePath(context);
	CGContextFillPath(context);

	UIGraphicsPopContext();
}

- (void)layoutSubviews {
	
	// Entirely cover the parent view
	UIView *parent = self.superview;
	if (parent) {
		self.frame = parent.bounds;
	}
	CGRect bounds = self.bounds;
	
	// Determine the total widt and height needed
	CGFloat maxWidth = bounds.size.width - 4 * margin;
	CGSize totalSize = CGSizeZero;
	
	CGRect indicatorF = indicator.bounds;
	indicatorF.size.width = MIN(indicatorF.size.width, maxWidth);
	totalSize.width = MAX(totalSize.width, indicatorF.size.width);
	totalSize.height += indicatorF.size.height;
	
	CGSize labelSize = [label.text sizeWithFont:label.font];
	labelSize.width = MIN(labelSize.width, maxWidth);
	totalSize.width = MAX(totalSize.width, labelSize.width);
	totalSize.height += labelSize.height;
	if (labelSize.height > 0.f && indicatorF.size.height > 0.f) {
		totalSize.height += kPadding;
	}

	CGFloat remainingHeight = bounds.size.height - totalSize.height - kPadding - 4 * margin; 
	CGSize maxSize = CGSizeMake(maxWidth, remainingHeight);
	CGSize detailsLabelSize = [detailsLabel.text sizeWithFont:detailsLabel.font 
								constrainedToSize:maxSize lineBreakMode:detailsLabel.lineBreakMode];
	totalSize.width = MAX(totalSize.width, detailsLabelSize.width);
	totalSize.height += detailsLabelSize.height;
	if (detailsLabelSize.height > 0.f && (indicatorF.size.height > 0.f || labelSize.height > 0.f)) {
		totalSize.height += kPadding;
	}
	
	totalSize.width += 2 * margin;
	totalSize.height += 2 * margin;
	
	// Position elements
	CGFloat yPos = roundf(((bounds.size.height - totalSize.height) / 2)) + margin + yOffset;
	CGFloat xPos = xOffset;
	indicatorF.origin.y = yPos;
	indicatorF.origin.x = roundf((bounds.size.width - indicatorF.size.width) / 2) + xPos;
	indicator.frame = indicatorF;
	yPos += indicatorF.size.height;
	
	if (labelSize.height > 0.f && indicatorF.size.height > 0.f) {
		yPos += kPadding;
	}
	CGRect labelF;
	labelF.origin.y = yPos;
	labelF.origin.x = roundf((bounds.size.width - labelSize.width) / 2) + xPos;
	labelF.size = labelSize;
	label.frame = labelF;
	yPos += labelF.size.height;
	
	if (detailsLabelSize.height > 0.f && (indicatorF.size.height > 0.f || labelSize.height > 0.f)) {
		yPos += kPadding;
	}
	CGRect detailsLabelF;
	detailsLabelF.origin.y = yPos;
	detailsLabelF.origin.x = roundf((bounds.size.width - detailsLabelSize.width) / 2) + xPos;
	detailsLabelF.size = detailsLabelSize;
	detailsLabel.frame = detailsLabelF;
	
	// Enforce minsize and quare rules
	if (square) {
		CGFloat max = MAX(totalSize.width, totalSize.height);
		if (max <= bounds.size.width - 2 * margin) {
			totalSize.width = max;
		}
		if (max <= bounds.size.height - 2 * margin) {
			totalSize.height = max;
		}
	}
	if (totalSize.width < minSize.width) {
		totalSize.width = minSize.width;
	} 
	if (totalSize.height < minSize.height) {
		totalSize.height = minSize.height;
	}
	
	self.size = totalSize;
}