开发中遇到的问题

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1.键盘透明

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textField.keyboardAppearance = UIKeyboardAppearanceAlert;

2.状态栏的网络活动风火轮是否旋转

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[UIApplication sharedApplication].networkActivityIndicatorVisible，默认值是NO。

3.NSMutableAttributedString 行间距、段落间距

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NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithString:dLabelString];  
NSMutableParagraphStyle   *paragraphStyle   = [[NSMutableParagraphStyle alloc] init];  

//行间距  
[paragraphStyle setLineSpacing:5.0];  
//段落间距  
[paragraphStyle setParagraphSpacing:10.0];  
//第一行头缩进  
[paragraphStyle setFirstLineHeadIndent:15.0];  
//头部缩进  
//[paragraphStyle setHeadIndent:15.0];  
//尾部缩进  
//[paragraphStyle setTailIndent:250.0];  
//最小行高  
//[paragraphStyle setMinimumLineHeight:20.0];  
//最大行高  
//[paragraphStyle setMaximumLineHeight:20.0];  
      
[attributedString addAttribute:NSParagraphStyleAttributeName value:paragraphStyle range:NSMakeRange(0, [dLabelString length])];  
[dLabel setAttributedText:attributedString];

4.跳转storyBoard

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1.获取第一个视图storyBoard
 /* 加载名为storyboardName的Storyboard */
 UIStoryboard *storyboard = [UIStoryboard storyboardWithName:storyboardName bundle:nil];
 
 /* 获取storyboard的InitialViewController 即根控制器*/
 FirstViewController *vc = [storyboard instantiateInitialViewController];
 其中UIViewController可以根据当前视图进行替换，替换成StoryBoard对应的视图类，然后选择跳转方式
 2.获取第二个视图storyboard的某个视图控制器的时候使用
  SecondViewController *VC= [storyboard instantiateViewControllerWithIdentifier:@"NewVC”];(这个过程需要在StoryBoard中设置目标视图的Custom Class和StoryBoard ID)
 //跳转事件的实现
 在第一个视图添加按钮跳转到第二个视图
 [self.navigationController pushViewController:VC animated:YES];(第一个视图是带有导航栏的)

5.用代码使程序转向设置页面：

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NSURL *url=[NSURL URLWithString:@"prefs:root=WIFI"];//转向->"设置wifi"页面
[[UIApplication sharedApplication] openURL:url];

6.系统判断

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#define isOperatingSystemAtLeastVersion(majorVersion, minorVersion, patchVersion)[[NSProcessInfo processInfo] isOperatingSystemAtLeastVersion: (NSOperatingSystemVersion) {
    majorVersion,
    minorVersion,
    patchVersion
}]

if (isOperatingSystemAtLeastVersion(11, 0, 0)) {
    //using new API
} else {
    //using deprecated API
}

7. web Cookies 每次退出应用都被清除解决方法( 用于实现自动登录 )https://www.jianshu.com/p/19a053e37c53

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NSHTTPCookieStorage* cookieStorage = [NSHTTPCookieStorage sharedHTTPCookieStorage];
    NSArray<NSHTTPCookie *> *cookies = [cookieStorage cookiesForURL:[NSURL URLWithString:baseUrl]];
    NSMutableArray<NSDictionary *> *propertiesList = [[NSMutableArray alloc] init];
    [cookies enumerateObjectsUsingBlock:^(NSHTTPCookie * _Nonnull cookie, NSUInteger idx, BOOL * _Nonnull stop) {
        NSMutableDictionary *properties = [[cookie properties] mutableCopy];
        //将cookie过期时间设置为一年后
        NSDate *expiresDate = [NSDate dateWithTimeIntervalSinceNow:3600*24*30*12];
        properties[NSHTTPCookieExpires] = expiresDate;
        //下面一行是关键,删除Cookies的discard字段，应用退出，会话结束的时候继续保留Cookies
        [properties removeObjectForKey:NSHTTPCookieDiscard];
         //重新设置改动后的Cookies
        [cookieStorage setCookie:[NSHTTPCookie cookieWithProperties:properties]];
    }];
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