ios - 为什么我的 NSString 不适合使用我的 NSString 宽度创建的框架？

Question

在我看来，我正在处理的代码应该是这样写的:

    if (!instructions)
{
    instructions = [[UITextView alloc] init];
    instructions.backgroundColor=[UIColor clearColor];
    instructions.font = [UIFont fontWithName:@"Helvetica Neue" size:12];
    instructions.editable=NO;
    instructions.text = @"\nFor millennia, the Japanese haiku has allowed great\nthinkers to express their ideas about the world in three\nlines of five, seven, and five syllables respectively.";

//THIS IS THE RELEVANT LINE:
    NSString *t = @"thinkers to express their ideas about the world in three"; //Using this to set width since it's the longest line of the string.

    CGSize thisSize = [t sizeWithFont:[UIFont fontWithName:@"Helvetica Neue" size:12]];
    float textWidth = thisSize.width;
    const int INSTRUCTIONS_HEIGHT=10; //I know this is an ugly hack.
    float textHeight = thisSize.height*INSTRUCTIONS_HEIGHT;
    instructions.frame = CGRectMake(screenWidth/2-textWidth/2, screenHeight/2-textHeight/2, textWidth, textHeight);
}

但输出看起来像这样，行必须环绕:



当我调整代码以在设置宽度的行中添加一些字符时:

    {
    instructions = [[UITextView alloc] init];
    instructions.backgroundColor=[UIColor clearColor];
    instructions.font = [UIFont fontWithName:@"Helvetica Neue" size:12];
    instructions.editable=NO;
    instructions.text = @"\nFor millennia, the Japanese haiku has allowed great\nthinkers to express their ideas about the world in three\nlines of five, seven, and five syllables respectively.";

//THIS IS THE LINE I CHANGED:
    NSString *t = @"thinkers to express their ideas about the world in three lin"; //

    CGSize thisSize = [t sizeWithFont:[UIFont fontWithName:@"Helvetica Neue" size:12]];
    float textWidth = thisSize.width;
    const int INSTRUCTIONS_HEIGHT=6; //Since there's no wraparound here I could reduce this number.
    float textHeight = thisSize.height*INSTRUCTIONS_HEIGHT;
    instructions.frame = CGRectMake(screenWidth/2-textWidth/2, screenHeight/2-textHeight/2, textWidth, textHeight);
}

输出看起来像我想要的:



为什么“思想家在三个方面表达他们对世界的想法”这一行不适合设置在“思想家在三个方面表达他们对世界的想法”这一行宽度处的 TextView ？

(显然我需要学习如何在屏幕上定位事物。例如，我还没有弄清楚“中心”，我怀疑这会解决我的很多问题。但这就是我正在使用的现在，我很好奇。)

Answer 1

您需要将 sizeWithFont 限制为 TextView 的宽度。

就像是:

drawnSize = [t sizeWithFont:[UIFont fontWithName:@"Helvetica Neue" size:12]
                 constrainedToSize:CGSizeMake(instructions.frame.size.width, 3000)
                 lineBreakMode:NSLineBreakByWordWrapping ] ;

您可能还需要从 TextView 中获取插图并从宽度中减去它们:

UIEdgeInsets edgeInsets = instructions.contentInset;
CGFloat totalwidth = instructions.frame.size.width - edgeInsets.left - edgeInsets.right;