iOS 11.0 iPhone X safeArea适配

• 使用安全区域的情况
  当视图部分处于非安全区域内时，SafeAreaInsets会返回非0的数值，若整个视图已经处在安全区域中，则SafeAreaInsets会返回UIEdgeInsetsZero

• iOS 11.0之后系统新增安全区域改变时的回调方法

UIViewController中新增：
- (void)viewSafeAreaInsetsDidChange;
UIView中新增：
- (void)viewSafeAreaInsetsDidChange；

• 通过安全区域变化来改变视图的位置

如果屏幕旋转，相应的安全区域也会变化，所以不比担心。
- (void)viewSafeAreaInsetsDidChange {
    [super viewSafeAreaInsetsDidChange];
    
    NSLog(@"viewSafeAreaInsetsDidChange-%@",NSStringFromUIEdgeInsets(self.view.safeAreaInsets));
    
    [self updateOrientation];
}

/**
 更新屏幕safearea frame
 */
- (void)updateOrientation {
    if (@available(iOS 11.0, *)) {
        CGRect frame = self.customerView.frame;
        frame.origin.x = self.view.safeAreaInsets.left;
        frame.size.width = self.view.frame.size.width - self.view.safeAreaInsets.left - self.view.safeAreaInsets.right;
        frame.size.height = self.view.frame.size.height - self.view.safeAreaInsets.bottom;
        self.customerView.frame = frame;
    } else {
        // Fallback on earlier versions
    }
}

safeArea.gif

说明：使用xib创建视图，工程适配8.0以上系统，xib inspector中未勾选Safe Aear Layout Guide选项(iOS 9.0前无Safe Area Layout Guide)。其中粉色为当前viewcontroller的view，紫色的部分属于安全区域内部分（自定义视图）。

• 增大安全区域
  iOS 11.0还有一个属性additionalSafeAreaInsets，可以用来扩展安全区域的大小，如：

if (@available(iOS 11.0, *)) {
        self.additionalSafeAreaInsets = UIEdgeInsetsMake(50, 50, 50, 50);
        NSLog(@"additionalSafeAreaInsets-%@",NSStringFromUIEdgeInsets(self.additionalSafeAreaInsets));
        NSLog(@"safeAreaInsets-%@",NSStringFromUIEdgeInsets(self.view.safeAreaInsets));
    } else {
        // Fallback on earlier versions
    }

打印结果如下：

2017-11-07 10:28:04.012543+0800 XIBLayoutDemo[78269:6690668] additionalSafeAreaInsets-{50, 50, 50, 50}
2017-11-07 10:28:04.012737+0800 XIBLayoutDemo[78269:6690668] safeAreaInsets-{0, 0, 0, 0}

但在viewSafeAreaInsetsDidChange方法中监测，已经得到相应的改变：

2017-11-07 10:32:49.425656+0800 XIBLayoutDemo[78269:6690668] viewSafeAreaInsetsDidChange-{50, 50, 84, 50}
2017-11-07 10:32:49.426402+0800 XIBLayoutDemo[78269:6690668] viewSafeAreaInsetsDidChange-{94, 50, 84, 50}
2017-11-07 10:32:49.427091+0800 XIBLayoutDemo[78269:6690668] viewSafeAreaInsetsDidChange-{50, 50, 84, 50}

已经在原来{0,0,34,0}的基础上变为{50,50,84,50}，上左下右各增加了50，上图变为下图所示：

iPhone X.png

• 在iOS 11中给navigationItem添加搜索框也是正确的

if (@available(iOS 11.0, *)) {        
        UISearchController *searchVC = [[UISearchController alloc] initWithSearchResultsController:nil];
        searchVC.searchResultsUpdater = self;
        searchVC.searchBar.delegate = self;
        searchVC.searchBar.placeholder = @"填写搜索文字";
        searchVC.searchBar.showsCancelButton = YES;
                
        UITextField *searchField = [searchVC.searchBar valueForKey:@"_searchField"];
        searchField.textColor = [UIColor redColor];
        searchField.returnKeyType = UIReturnKeyGo;
        
        self.navigationItem.searchController = searchVC;
        self.navigationItem.hidesSearchBarWhenScrolling = YES;
    }

进入页面日志打印如下：

2017-11-08 10:27:56.488194+0800 XIBLayoutDemo[82378:7134741] viewSafeAreaInsetsDidChange-{0, 0, 34, 0}
2017-11-08 10:27:56.488650+0800 XIBLayoutDemo[82378:7134741] viewSafeAreaInsetsDidChange-{44, 0, 34, 0}
2017-11-08 10:27:56.489282+0800 XIBLayoutDemo[82378:7134741] viewSafeAreaInsetsDidChange-{0, 0, 34, 0}

searchController.png