ios - 正确使用 DrawRect 覆盖 - 我可以防止 View 拉伸(stretch)吗？

Question

编辑:下面详细问题的简化版本:您可以通过子类 drawRect 更新 UIView 的边界而不导致 View 内容拉伸(stretch)吗？

我正在构建一个新闻阅读器应用程序，并且一直在研究如何将 UIView 拆分为列并仍然对内容进行分页。我相信我已经对列进行了基本编码(将 XML 节点内容按段落拆分为数组，然后通过检测不切断段落所需的总面积进行解析。)

我遇到的问题是我无法在没有文本拉伸(stretch)的情况下更新 ContentBounds，即使里面的内容足够大以支持未拉伸(stretch)的 View 。

基本上是这样的:

contentBounds = CGSizeMake(self.bounds.size.width, self.bounds.size.height+COLUMN_YPOS);

[renderer updateContentBounds:contentBounds];

导致这个:(下图的完整代码)

- (void)drawRect:(CGRect)rect
{

NSString *string = contentString;
[string stringByReplacingOccurrencesOfString:@"<br>" withString:@"\n\n"];

// column width
int COLUMN_WIDTH = self.bounds.size.width/2-40;
int COLUMN_HEIGHT = self.bounds.size.height-100;

int COLUMN_XPOS = 20;
int COLUMN_YPOS = 0;

int PAGE_HEIGHT = COLUMN_HEIGHT + 40;

CGSize maximumSize = CGSizeMake(COLUMN_WIDTH, COLUMN_HEIGHT-20);

NSArray *paragraphs = [string componentsSeparatedByString:@"\n"];

NSString *textBuffer = @"";
NSString *preBuffer = @"";
NSString *currentStringSegment;

for (int i=0; i<[paragraphs count]; i++) {

    currentStringSegment = [paragraphs objectAtIndex:i];

    preBuffer = textBuffer;
    textBuffer = [textBuffer stringByAppendingString:@"\n\n"];
    textBuffer = [textBuffer stringByAppendingString:currentStringSegment];

    CGSize expectedSize = [textBuffer sizeWithFont:[UIFont fontWithName:@"Times New Roman" size:16] constrainedToSize:CGSizeMake(COLUMN_WIDTH, COLUMN_HEIGHT) lineBreakMode:NSLineBreakByWordWrapping];

    if(expectedSize.height > maximumSize.height){

        [preBuffer drawInRect:CGRectMake(COLUMN_XPOS, COLUMN_YPOS, COLUMN_WIDTH, COLUMN_HEIGHT) withFont:[UIFont fontWithName:@"Times New Roman" size:16] lineBreakMode:NSLineBreakByWordWrapping alignment:NSTextAlignmentLeft];
        i--;
        textBuffer = @"";
        preBuffer = @"";

        if(COLUMN_XPOS > 20) {

            COLUMN_XPOS = 20;
            COLUMN_YPOS += PAGE_HEIGHT;

        } else {

            COLUMN_XPOS = COLUMN_WIDTH + 60;

        }

    }

}

if(![preBuffer isEqualToString:@""] && preBuffer != nil){

    [preBuffer drawInRect:CGRectMake(COLUMN_XPOS, COLUMN_YPOS, COLUMN_WIDTH, COLUMN_HEIGHT) withFont:[UIFont fontWithName:@"Times New Roman" size:16] lineBreakMode:NSLineBreakByWordWrapping alignment:NSTextAlignmentLeft];

}

contentBounds = CGSizeMake(self.bounds.size.width, self.bounds.size.height);

[renderer updateContentBounds:contentBounds];

}

Answer 1

UIView 的行为当边界变化由 contentMode 确定时属性(property)。

如果你看看 documentation你会读到:

the value in the contentMode property determines whether the bitmap should be scaled to fit the new bounds or simply pinned to one corner or edge of the view.

默认 contentMode设置为 UIViewContentModeScaleToFill正如您可以在同一个文档页面中阅读的那样，

causes the view’s contents to be scaled to fit the new frame size.

您可能想要更改 contentMode您对非扭曲行为的看法，例如 UIViewContentModeTop ，这将使对齐在 View 边界顶部的内容居中。

您可以找到 contentMode 的所有可能值 here .