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

 1 #import "UIView+Log.h"
 2
 3 @implementation UIView (Log)
 4
 5 + (NSString *)searchAllSubviews:(UIView *)superview
 6 {
 7     NSMutableString *xml = [NSMutableString string];
 8
 9     NSString *class = NSStringFromClass(superview.class);
10     // 部分控件的类名带下划线_,XML里含下划线_会报错
11     class = [class stringByReplacingOccurrencesOfString:@"_" withString:@""];
12
13     if ([class isEqualToString:@"UIScrollView"]) {
14         UIScrollView *realView= (UIScrollView *)superview;
15         [xml appendFormat:@"<%@ frame=\"%@\" contentSize=\"%@\" >\n", class, NSStringFromCGRect(superview.frame),NSStringFromCGSize(realView.contentSize)];
16     }else{
17         [xml appendFormat:@"<%@ frame=\"%@\">\n", class, NSStringFromCGRect(superview.frame)];
18     }
19
20     for (UIView *childView in superview.subviews) {
21         NSString *subviewXml = [self searchAllSubviews:childView];
22         [xml appendString:subviewXml];
23     }
24     [xml appendFormat:@"</%@>\n", class];
25     return xml;
26
27 }
28
29 - (NSString *)description
30 {
31     return [UIView searchAllSubviews:self];
32 }
33
34 @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