ios开发中计算字符串的高度

NSString *aString =@"真正爱上一个人的时候，一切都那么值得，包括不可避免的伤害.";

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UIFont *font = [UIFont systemFontOfSize:17];

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//第一种算法，ios7.0后已经废弃

CGSize titleSize = [aString sizeWithFont:font constrainedToSize:CGSizeMake(@"label的宽度", MAXFLOAT) lineBreakMode:UILineBreakModeWordWrap];

//第二种算法ios7.0 后计算字符串的高度

CGRect rect = [aString boundingRectWithSize:CGSizeMake(@"label的宽度", MAXFLOAT) options:NSStringDrawingUsesLineFragmentOrigin attributes:@{NSFontAttributeName : font} context:nil];

 NSLog(@"Height:::%f",rect.size.height);

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//自己封装的方法

-(CGSize)sizeWithFont:(UIFont *)font maxSize:(CGSize)maxSize string:(NSString *)string{

NSDictionary *attrs = @{NSFontAttributeName:font};

return [string boundingRectWithSize:maxSize options:NSStringDrawingUsesLineFragmentOrigin attributes:attrs context:nil].size;

}

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//例子

//此处1000为高度 还可以换为：MAXFLOAT

-(void)ViewDidload{

CGSizestringSize=[self sizeWithFont:font maxSize:CGSizeMake(SCREEN_WIDTH-20, 1000)string:aString];

float  textH= stringSize.height;

NSLog(@"textH:::%f",textH);

}

补：如果要自适应label高度，label还应该设置：label.numberOfLines =0;