iphone - 加载 ScrollView 性能不佳

Question

我有一个 View Controller ，其 View 由一个由 2 个按钮(上一个和下一个)控制的分页 ScrollView 组成。在这个 ScrollView 中有几个自定义 View ，每个都是一页的大小。

当我加载主视图时， ScrollView 被设置为包含所有这些 subview 。我的应用程序的性能目前在这方面是 Not Acceptable ，因为加载 View 大约需要 3 秒。我注意到如果我在我的自定义 View 上注释掉我的 drawrect 方法，性能会显着提高。有人可以看一下这段代码，看看我在做什么，这太耗费资源了吗？我对核心图形真的很陌生，怀疑我做的事情显然是错误的。

谢谢

- (void)drawRect:(CGRect)rect {
    UILabel *questionNumberLabel = [[UILabel alloc] initWithFrame:CGRectMake(10, 40, 200, 50)];
    [questionNumberLabel setBackgroundColor:[UIColor clearColor]];
    [questionNumberLabel setText:[NSString stringWithFormat:@"Question %i", surveyQuestionNumber]];
    [questionNumberLabel setTextAlignment:UITextAlignmentCenter];
    [questionNumberLabel setFont:[UIFont boldSystemFontOfSize:28.0]];
    [questionNumberLabel setTextColor:[UIColor whiteColor]];
    [questionNumberLabel setShadowOffset:CGSizeMake(0, -1.0)];
    [questionNumberLabel setShadowColor:[UIColor colorWithRed:0.0 green:0.0 blue:0.0 alpha:0.5]];
    [self addSubview:questionNumberLabel];
    [questionNumberLabel release];

    CGContextRef context = UIGraphicsGetCurrentContext();

    CGColorRef whiteColor = [UIColor colorWithRed:1.0 green:1.0 blue:1.0 alpha:1.0].CGColor; 
    CGColorRef lightGrayColor = [UIColor colorWithRed:230.0/255.0 green:230.0/255.0 blue:230.0/255.0 alpha:1.0].CGColor;
    CGColorRef shadowColor = [UIColor colorWithRed:0.2 green:0.2 blue:0.2 alpha:0.5].CGColor;
    CGColorRef lightGreenColor = [[UIColor colorWithRed:158.0/255.0 green:192.0/255.0 blue:72.0/255.0 alpha:1.0] CGColor];
    CGColorRef darkGreenColor = [[UIColor colorWithRed:102.0/255.0 green:142.0/255.0 blue:66.0/255.0 alpha:1.0] CGColor];
    CGColorRef shadowGreenColor = [[UIColor colorWithRed:71.0/255.0 green:100.0/255.0 blue:66.0/255.0 alpha:1.0] CGColor];

    CGFloat outerMargin = 20.0f;
    CGRect outerRect = CGRectInset(self.bounds, outerMargin, outerMargin);
    CGMutablePathRef outerPath = createRoundedRectForRect(outerRect, 15.0);

    CGContextSaveGState(context);
    CGContextSetFillColorWithColor(context, whiteColor);
    CGContextSetShadowWithColor(context, CGSizeMake(0, 5), 5.0, shadowColor);
    CGContextAddPath(context, outerPath);
    CGContextFillPath(context);
    CGContextRestoreGState(context);

    CGContextSaveGState(context);
    CGContextAddPath(context, outerPath);
    CGContextClip(context);
    drawLinearGradient(context, outerRect, whiteColor, lightGrayColor);
    CGContextRestoreGState(context);

    CGContextSaveGState(context);
    CGContextSetLineWidth(context, 2.0);
    CGContextSetStrokeColorWithColor(context, whiteColor);
    CGContextAddPath(context, outerPath);
    CGContextStrokePath(context);
    CGContextRestoreGState(context);

    CGRect ribbonyRect = CGRectMake(10, 40, 220, 50);
    CGContextSaveGState(context);
    CGMutablePathRef ribbonPath = CGPathCreateMutable();
    CGPathMoveToPoint(ribbonPath, NULL, ribbonyRect.origin.x, ribbonyRect.origin.y);
    CGPathAddLineToPoint(ribbonPath, NULL, ribbonyRect.origin.x+ribbonyRect.size.width, ribbonyRect.origin.y);
    CGPathAddLineToPoint(ribbonPath, NULL, ribbonyRect.origin.x+ribbonyRect.size.width-20, ribbonyRect.origin.y+((ribbonyRect.size.height)/2));
    CGPathAddLineToPoint(ribbonPath, NULL, ribbonyRect.origin.x+ribbonyRect.size.width, ribbonyRect.origin.y+ribbonyRect.size.height);
    CGPathAddLineToPoint(ribbonPath, NULL, ribbonyRect.origin.x, ribbonyRect.origin.y+ribbonyRect.size.height);
    CGPathCloseSubpath(ribbonPath);


    CGContextSaveGState(context);
    CGContextSetShadowWithColor(context, CGSizeMake(0, 5), 5.0, shadowColor);
    CGContextAddPath(context, ribbonPath);
    CGContextFillPath(context);
    CGContextRestoreGState(context);

    CGContextAddPath(context, ribbonPath);
    CGContextClip(context);
    drawLinearGradient(context, ribbonyRect, lightGreenColor, darkGreenColor);
    CGContextRestoreGState(context);



    CGContextSaveGState(context);
    CGContextAddPath(context, ribbonPath);
    CGContextSetLineWidth(context, 2.0);
    CGContextSetStrokeColorWithColor(context, lightGreenColor);
    CGContextStrokePath(context);
    CGContextRestoreGState(context);

    CGContextSaveGState(context);
    CGContextAddPath(context, ribbonPath);
    CGContextSetLineWidth(context, 1.5);
    CGContextSetStrokeColorWithColor(context, darkGreenColor);
    CGContextStrokePath(context);
    CGContextRestoreGState(context);


    CGContextMoveToPoint(context, ribbonyRect.origin.x, ribbonyRect.origin.y+ribbonyRect.size.height+1.5);
    CGContextAddLineToPoint(context, 19.0, ribbonyRect.origin.y+ribbonyRect.size.height+1.5);
    CGContextAddLineToPoint(context, 19.0, ribbonyRect.origin.y+ribbonyRect.size.height+12.0);
    CGContextSetFillColorWithColor(context, shadowGreenColor);
    CGContextFillPath(context);

    CFRelease(ribbonPath);
    CFRelease(outerPath);

    questionTitleLabel = [[UILabel alloc] initWithFrame:CGRectMake(100.0, 110.0, 568.0, 100.0)];
    [questionTitleLabel setBackgroundColor:[UIColor clearColor]];
    [questionTitleLabel setText:[currentQuestion questionTitle]];
    [questionTitleLabel setFont:[UIFont systemFontOfSize:30.0]];
    [questionTitleLabel setTextAlignment:UITextAlignmentCenter];
    [questionTitleLabel setTextColor:[UIColor grayColor]];
    [questionTitleLabel setShadowColor:[UIColor whiteColor]];
    [questionTitleLabel setShadowOffset:CGSizeMake(0, -1.0)];
    [questionTitleLabel setLineBreakMode:UILineBreakModeWordWrap];
    [questionTitleLabel setNumberOfLines:0];
    [self addSubview:questionTitleLabel];


    questionHintLabel = [[UILabel alloc] initWithFrame:CGRectMake(100.0, 215.0, 568.0, 30.0)];
    [questionHintLabel setBackgroundColor:[UIColor clearColor]];
    [questionHintLabel setText:[currentQuestion questionHint]];
    [questionHintLabel setFont:[UIFont italicSystemFontOfSize:15.0]];
    [questionHintLabel setTextAlignment:UITextAlignmentCenter];
    [questionHintLabel setTextColor:[UIColor grayColor]];
    [questionHintLabel setShadowColor:[UIColor whiteColor]];
    [questionHintLabel setShadowOffset:CGSizeMake(0, -1.0)];
    [self addSubview:questionHintLabel];
}

我已经对我的最新代码做了一个要点。如果有人能看一下here , 我真的很感激

Answer 1

我突然想到两件事。

1.) 在别处实例化您的 UILabels - 可能在 -viewDidLoad 中。并在 -viewDidLoad 中对 UILabels 进行必要的设置。更新对象需要时间。因此，将 questionXxxLabel 对象设置为 ivars。

2.) 按照相同的思路，在其他地方创建那些 CGColorRefs。它们可以是静态类变量或 ivars - 但它们应该只定义一次。

例如，您可以创建一个 colors.h 文件，该文件可以包含在可能使用这些颜色的位置。

 /*
 * colors.h
 */

//  use _COLORS_ to insure that colors.h is not included multiple times
//  i.e., ANSI standard way of constructing an inclusion guard.

#ifndef _COLORS_
#define _COLORS_

CGColorRef whiteColor = [UIColor colorWithRed:1.0 green:1.0 blue:1.0 alpha:1.0].CGColor; 
CGColorRef lightGrayColor = [UIColor colorWithRed:230.0/255.0 green:230.0/255.0 blue:230.0/255.0 alpha:1.0].CGColor;
CGColorRef shadowColor = [UIColor colorWithRed:0.2 green:0.2 blue:0.2 alpha:0.5].CGColor;
CGColorRef lightGreenColor = [[UIColor colorWithRed:158.0/255.0 green:192.0/255.0 blue:72.0/255.0 alpha:1.0] CGColor];
CGColorRef darkGreenColor = [[UIColor colorWithRed:102.0/255.0 green:142.0/255.0 blue:66.0/255.0 alpha:1.0] CGColor];
CGColorRef shadowGreenColor = [[UIColor colorWithRed:71.0/255.0 green:100.0/255.0 blue:66.0/255.0 alpha:1.0] CGColor];

#endif // _COLORS_