2018.7.9
方法定义#
- (NSRect)boundingRectWithSize:(NSSize)size
options:(NSStringDrawingOptions)options
attributes:(NSDictionary<NSAttributedStringKey, id> *)attributes
context:(NSStringDrawingContext *)context;参数定义#
size#
绘制的限制size，计算出来的值不会超过这个大小。
options#
一些配置项。定义如下：
typedef NS_OPTIONS(NSInteger, NSStringDrawingOptions) {
NSStringDrawingUsesLineFragmentOrigin = 1 << 0, // The specified origin is the line fragment origin, not the base line origin
NSStringDrawingUsesFontLeading = 1 << 1, // Uses the font leading for calculating line heights
NSStringDrawingUsesDeviceMetrics = 1 << 3, // Uses image glyph bounds instead of typographic bounds
NSStringDrawingTruncatesLastVisibleLine NS_ENUM_AVAILABLE(10_5, 6_0) = 1 << 5, // Truncates and adds the ellipsis character to the last visible line if the text doesn't fit into the bounds specified. Ignored if NSStringDrawingUsesLineFragmentOrigin is not also set.
} NS_ENUM_AVAILABLE(10_0, 6_0);实际测试使用NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading可以满足需求，NSStringDrawingUsesLineFragmentOrigin是必须的，NSStringDrawingUsesFontLeading加不加在测试的时候没发现区别，但是在stackoverflow相关讨论里加上了，留个坑，后面知道为什么了来补充吧。
attributes#
字体
context#
上下文
注意事项#
- 如果是多行文字，options要加上
NSStringDrawingUsesLineFragmentOrigin - 返回的值是小数，需要调用
ceil向上取整 - 得到的宽度可能比实际宽
代码示例#
+ (CGSize)getTextLabelSize:(NSString *)message {
if ([message length] > 0) {
// 文本框的最大宽度
float maxWidth = 200;
CGRect textRect = [message
boundingRectWithSize:CGSizeMake(maxWidth, CGFLOAT_MAX)
options:(NSStringDrawingUsesLineFragmentOrigin |
NSStringDrawingUsesFontLeading)
attributes:@{
NSFontAttributeName :
[UIFont systemFontOfSize:16]
}
context:nil];
textRect.size.height = ceilf(textRect.size.height);
textRect.size.width = ceilf(textRect.size.width);
return CGSizeMake(textRect.size.width, textRect.size.height);
} else {
return CGSizeZero;
}
}
