iOS - 将我的 CATextLayer 框架添加到 UIScrollView 的问题

Posted 2023-03-16

【中文标题】iOS - 将我的 CATextLayer 框架添加到 UIScrollView 的问题

【英文标题】：iOS - Issue adding my CATextLayer frame to a UIScrollView

【发布时间】：2013-01-29 02:14:19

【问题描述】：

我正在尝试将我的 CATextLayer 框架添加到 UIScrollView 以获得一些滚动。我一直在尝试使用此处提到的技术 (How can i make my CATextLayer object Scrollable like UITextView?)，但没有成功。

实际上，由于我在代码中添加了（建议的）3 行代码，我的 CATextLayer 不再显示。

我在下面附上了我的代码并注意到了这 3 行。也许有人可以帮我解决这个问题，甚至提出一个更好的方法来解决这个问题:-)

// Create the scrool view (FIRST LINE ADDED)
UIScrollView* scrollLayer = [[UIScrollView alloc] initWithFrame:CGRectMake(0.0, 0.0, 500.0, 500.0)];

// Create the new layer object
boxLayer = [[CATextLayer alloc] init];

// Give it a size
[boxLayer setBounds:CGRectMake(0.0, 0.0, 500.0, 500.0)];

// Give it a location
[boxLayer setPosition:CGPointMake(300.0, 350.0)];

// Make half-transparent red the background color for the layer
UIColor *reddish = [UIColor colorWithRed:0.0 green:0.0 blue:0.0 alpha:0.1];

// Get CGColor object with the same color values
CGColorRef cgReddish = [reddish CGColor];
[boxLayer setBackgroundColor:cgReddish];

// Make it a sublayer on the view's layer
[self.view.layer addSublayer:boxLayer];

// Create string
NSString *text2 = @"The article was about employment.\nHe leafed through it in an instant.\nHis feeling of anxiety resurfaced and he closed the magazine.\n\n-Hm…, he breathed.\n\n-Have you been looking for work long?, asked the stranger at his side.\nThe article was about employment.\nHe leafed through it in an instant.\nHis feeling of anxiety resurfaced and he closed the magazine.\n\n-Hm…, he breathed.\n\n-Have you been looking for work long?, asked the stranger at his side.\nThe article was about employment.\nHe leafed through it in an instant.\nHis feeling of anxiety resurfaced and he closed the magazine.\n\n-Hm…, he breathed.\n\n-Have you been looking for work long?, asked the stranger at his side.";


// Set font type
[boxLayer setFont:@"MarkerFelt-Thin"];

// Set font size
[boxLayer setFontSize:20.0];

// Text is left justified
[boxLayer setAlignmentMode:kCAAlignmentLeft];

// Text is wrapped
boxLayer.wrapped = YES;

// Assign string to layer
[boxLayer setString:text2];

// Define the text size (SECOND LINE ADDED)
scrollLayer.contentSize = CGSizeMake(500, 1000);

// Set the text layer as a sub layer of the scroll view (THIRD LINE ADDED)
[scrollLayer.layer addSublayer:boxLayer];

【参考方案1】：

根据我们对另一个讨论的讨论，我想知道您是否应该添加CATextLayer 对象。例如，您可以添加 UILabel 对象。例如，让我们在滚动视图中添加一系列UILabel 对象：

- (void)viewDidAppear:(BOOL)animated

    [super viewDidAppear:animated];

    if (!self.addedLabels)
    
        [self addLabelsToScrollView:self.scrollView];
        self.addedLabels = YES;
    


- (void)addLabelsToScrollView:(UIScrollView *)scrollView

    NSArray *gettysburgAddress = @[
                                   @"Four score and seven years ago our fathers brought forth on this continent a new nation, conceived in liberty, and dedicated to the proposition that all men are created equal.",
                                   @"Now we are engaged in a great civil war, testing whether that nation, or any nation, so conceived and so dedicated, can long endure. We are met on a great battle-field of that war. We have come to dedicate a portion of that field, as a final resting place for those who here gave their lives that that nation might live. It is altogether fitting and proper that we should do this.",
                                   @"But, in a larger sense, we can not dedicate, we can not consecrate, we can not hallow this ground. The brave men, living and dead, who struggled here, have consecrated it, far above our poor power to add or detract. The world will little note, nor long remember what we say here, but it can never forget what they did here. It is for us the living, rather, to be dedicated here to the unfinished work which they who fought here have thus far so nobly advanced. It is rather for us to be here dedicated to the great task remaining before us—that from these honored dead we take increased devotion to that cause for which they gave the last full measure of devotion—that we here highly resolve that these dead shall not have died in vain—that this nation, under God, shall have a new birth of freedom—and that government of the people, by the people, for the people, shall not perish from the earth."
                                  ];

    CGFloat y = 0.0;
    UIFont *font = [UIFont fontWithName:@"MarkerFelt-Thin" size:20.0];
    CGSize maxSize = CGSizeMake(scrollView.frame.size.width, 10000.0);

    for (NSString *line in gettysburgAddress)
    
        CGSize labelSize = [line sizeWithFont:font constrainedToSize:maxSize lineBreakMode:NSLineBreakByWordWrapping];
        CGRect labelFrame = CGRectMake(0.0, y, labelSize.width, labelSize.height);
        UILabel *label = [[UILabel alloc] initWithFrame:labelFrame];
        label.font = font;
        label.text = line;
        label.numberOfLines = 0;
        [scrollView addSubview:label];

        y += labelSize.height + 16.0;
    

    scrollView.contentSize = CGSizeMake(scrollView.contentSize.width, y);

或者更简单，而不是将UILabel 对象添加到UIScrollView，您可以只使用UITextView：

- (void)updateTextView

    NSArray *gettysburgAddress = @[
                                   @"Four score and seven years ago our fathers brought forth on this continent a new nation, conceived in liberty, and dedicated to the proposition that all men are created equal.",
                                   @"Now we are engaged in a great civil war, testing whether that nation, or any nation, so conceived and so dedicated, can long endure. We are met on a great battle-field of that war. We have come to dedicate a portion of that field, as a final resting place for those who here gave their lives that that nation might live. It is altogether fitting and proper that we should do this.",
                                   @"But, in a larger sense, we can not dedicate, we can not consecrate, we can not hallow this ground. The brave men, living and dead, who struggled here, have consecrated it, far above our poor power to add or detract. The world will little note, nor long remember what we say here, but it can never forget what they did here. It is for us the living, rather, to be dedicated here to the unfinished work which they who fought here have thus far so nobly advanced. It is rather for us to be here dedicated to the great task remaining before us—that from these honored dead we take increased devotion to that cause for which they gave the last full measure of devotion—that we here highly resolve that these dead shall not have died in vain—that this nation, under God, shall have a new birth of freedom—and that government of the people, by the people, for the people, shall not perish from the earth."
                                  ];

    NSString *text = [gettysburgAddress componentsJoinedByString:@"\n\n"];

    self.textView.text = text;
    self.textView.font = [UIFont fontWithName:@"MarkerFelt-Thin" size:20.0];
    self.textView.editable = NO;

这一切都取决于您是否真的需要使用CATextLayer。

【讨论】：

谢谢...我将取消 CATextLayer。这是我们讨论之前我知道的唯一技术:-)