iOS UI控件没有显示时的调试技巧

1.遇到UI控件没有显示的问题,可以给这个控件设置背景色

假设这个控件是UIBUtton

如果背景色能显示,那问题就出在image和title值为空

如果背景色不能显示,重写控件的description方法,把控件的frame打印出来分析

2.以下是打印UIView的frame的分类

#import <UIKit/UIKit.h>
@interface UIView (Log)
@end

#import "UIView+Log.h"

@implementation UIView (Log)

+ (NSString *)searchAllSubviews:(UIView *)superview
{
    NSMutableString *xml = [NSMutableString string];
    
    NSString *class = NSStringFromClass(superview.class);
    // 部分控件的类名带下划线_,XML里含下划线_会报错
    class = [class stringByReplacingOccurrencesOfString:@"_" withString:@""]; 

    if ([class isEqualToString:@"UIScrollView"]) {
        UIScrollView *realView= (UIScrollView *)superview;
        [xml appendFormat:@"<%@ frame="%@" contentSize="%@" >
", class, NSStringFromCGRect(superview.frame),NSStringFromCGSize(realView.contentSize)];
    }else{
        [xml appendFormat:@"<%@ frame="%@">
", class, NSStringFromCGRect(superview.frame)];
    }

    for (UIView *childView in superview.subviews) {
        NSString *subviewXml = [self searchAllSubviews:childView];
        [xml appendString:subviewXml];
    }
    [xml appendFormat:@"</%@>
", class];
    return xml;

}

- (NSString *)description
{
    return [UIView searchAllSubviews:self];
}

@end

3. 利用上面的分类,就可以很方便的打印UI控件,把打印的信息粘在XML文件里,用火狐打开,便于浏览