iOS中safe area對scrollView的內(nèi)容偏移產(chǎn)生的影響(iOS11的適配問題)

scrollview的幾個關鍵屬性

contentSize: 就是scrollView可以滾動的區(qū)域. 例如 frame = (0,0, 320, 480), contentSize = (320, 960), 代表scrollView可以上下滾動, 滾動區(qū)域為frame大小的兩倍.

contentOffset 是scrollview當前顯示區(qū)域頂點相對于frame頂點的偏移量, 比如上一個例子中, 將scrollView拉到最下面, 那么contentOffset = (0, 480), 也就是 y 偏移了480.

contentInset是scrollView中的contentView.frame.origin和scrollView.frame.origin之間的關系. 例如contentView.frame = (0, 30, 320, 480), 那么contentInset = (0, 30)

iOS11 新加入的屬性 adjustedContentInset: 表示scrollView的內(nèi)容的自適應內(nèi)邊距, 它的取值和contentInsetAdjustmentBehavior枚舉屬性息息相關, 同時取消vc.automaticallyAdjustsScrollViewInsets屬性值.

scrollView關鍵屬性的實踐(一)

vc在navigationController中, navigationBar是默認狀態(tài), 并且self.automaticallyAdjustsScrollViewInsets = YES和scrollView.contentInsetAdjustmentBehavior = UIScrollViewContentInsetAdjustmentAutomatic;都是使用的默認值.(注意如果當前vc沒有在navigationController或者TabbarController中時候, 結果可能不一樣, 我們一般討論的是scrollView在navigationController中的情況)

-(void)viewDidLoad{
    UIScrollView *scrollView = [[UIScrollView alloc] init];
    scrollView.backgroundColor = [UIColor whiteColor];
    [self.view addSubview:scrollView];
    scrollView.frame = self.view.bounds;
    scrollView.contentSize = CGSizeMake(self.view.bounds.size.width, self.view.bounds.size.height * 2);
    self.scrollView = scrollView;

    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    [scrollView addSubview:button];
    button.frame = CGRectMake(0, 0, 100, 100);
    button.backgroundColor = [UIColor grayColor];
    [button addTarget:self action:@selector(buttonDidClick) forControlEvents:UIControlEventTouchUpInside];
    if (@available(iOS 11.0, *)) {
        scrollView.contentInsetAdjustmentBehavior = UIScrollViewContentInsetAdjustmentAutomatic;
    } else {
        self.automaticallyAdjustsScrollViewInsets = YES;
    }
}

在iOS8上:
2018-09-27 14:49:13.103 scrollViewInVcDemo[56036:1691899] contentInset: {64, 0, 0, 0}
2018-09-27 14:49:13.103 scrollViewInVcDemo[56036:1691899] contentOffset: {0, -64}

在iOS11上:
2018-09-27 14:47:23.731497+0800 scrollViewInVcDemo[55894:1682631] contentInset: {0, 0, 0, 0}
2018-09-27 14:47:23.731605+0800 scrollViewInVcDemo[55894:1682631] contentOffset: {0, -64}
2018-09-27 14:47:23.731708+0800 scrollViewInVcDemo[55894:1682631] safeArea: {64, 0, 0, 0}
2018-09-27 14:47:23.731867+0800 scrollViewInVcDemo[55894:1682631] adjustedContentInset: {64, 0, 0, 0}

最終界面展示是一致的, 正方形的button 位于界面的左上方, navBar下:

image.png

上述代碼中, 如果設置self.navigationController.navigationBar.hidden = YES;, 得到的結果如下:

iOS8:
2018-09-27 15:16:04.581 scrollViewInVcDemo[57368:1792003] contentInset: {20, 0, 0, 0}
2018-09-27 15:16:04.581 scrollViewInVcDemo[57368:1792003] contentOffset: {0, -20}

iOS11:
2018-09-27 15:16:56.342570+0800 scrollViewInVcDemo[57444:1799639] contentInset: {0, 0, 0, 0}
2018-09-27 15:16:56.342685+0800 scrollViewInVcDemo[57444:1799639] contentOffset: {0, -20}
2018-09-27 15:16:56.342787+0800 scrollViewInVcDemo[57444:1799639] safeArea: {20, 0, 0, 0}
2018-09-27 15:16:56.342894+0800 scrollViewInVcDemo[57444:1799639] adjustedContentInset: {20, 0, 0, 0}

image.png

可以得出結論:

iOS10以前通過設置self.automaticallyAdjustsScrollViewInsets = YES;可以改變scrollView的contentInset, 從而使得scrollView上的元素不會被navigationBar或者tabbar遮擋.
在iOS11以后.則通過設置contentInsetAdjustmentBehavior屬性來改變adjustedContentInset屬性, 來完成相同效果, 同時contentInset屬性并未修改.并且automaticallyAdjustsScrollViewInsets屬性失效.

scrollView關鍵屬性的實踐(二)

如果我們設置如下關鍵屬性:

    self.navigationController.navigationBar.hidden = NO;
    if (@available(iOS 11.0, *)) {
        scrollView.contentInsetAdjustmentBehavior = UIScrollViewContentInsetAdjustmentNever;
    } else {
        self.automaticallyAdjustsScrollViewInsets = NO;
    }

得到的結論如下:

/**
 iOS 8:
 2018-10-08 16:30:31.331 scrollViewInVcDemo[3018:165133] scrollView: <UIScrollView: 0x7fddcec31390; frame = (0 0; 375 667); clipsToBounds = YES; gestureRecognizers = <NSArray: 0x7fddcec32050>; layer = <CALayer: 0x7fddcec318c0>; contentOffset: {0, 0}; contentSize: {375, 1334}>
 2018-10-08 16:30:31.331 scrollViewInVcDemo[3018:165133] contentInset: {0, 0, 0, 0}
 2018-10-08 16:30:31.332 scrollViewInVcDemo[3018:165133] contentOffset: {0, 0}

 iOS 11:
 2018-10-08 16:36:40.084890+0800 scrollViewInVcDemo[3252:188595] scrollView: <UIScrollView: 0x7ffd2d837000; frame = (0 0; 375 667); clipsToBounds = YES; gestureRecognizers = <NSArray: 0x60000097a8b0>; layer = <CALayer: 0x6000007447a0>; contentOffset: {0, 0}; contentSize: {375, 1334}; adjustedContentInset: {0, 0, 0, 0}>
 2018-10-08 16:36:40.085049+0800 scrollViewInVcDemo[3252:188595] contentInset: {0, 0, 0, 0}
 2018-10-08 16:36:40.085251+0800 scrollViewInVcDemo[3252:188595] contentOffset: {0, 0}
 2018-10-08 16:36:40.085379+0800 scrollViewInVcDemo[3252:188595] safeArea: {64, 0, 0, 0}
 2018-10-08 16:36:40.085521+0800 scrollViewInVcDemo[3252:188595] adjustedContentInset: {0, 0, 0, 0}
 */

兩者結果都如下圖:

image.png

可以得出結論:

iOS10以前通過設置self.automaticallyAdjustsScrollViewInsets = NO ;與在iOS11以后設置contentInsetAdjustmentBehavior=UIScrollViewContentInsetAdjustmentNever屬性是等效的.
contentInsetAdjustmentBehavior=UIScrollViewContentInsetAdjustmentNever屬性時候會有如下關系: adjustedContentInset == contentInset

iOS11以后, `contentInsetAdjustmentBehavior`與`adjustedContentInset`的關系

UIScrollViewContentInsetAdjustmentAutomatic：
如果scrollview在一個automaticallyAdjustsScrollViewContentInset = YES的controller上仇冯，并且這個Controller包含在一個navigationController中咒循，這種情況下會設置在top & bottom上 adjustedContentInset = safeAreaInset + contentInset(不管是否滾動)。其他情況下與UIScrollViewContentInsetAdjustmentScrollableAxes相同.
UIScrollViewContentInsetAdjustmentScrollableAxes:
在可滾動方向上adjustedContentInset = safeAreaInset + contentInset埃撵，在不可滾動方向上adjustedContentInset = contentInset；依賴于scrollEnabled和alwaysBounceHorizontal / vertical = YES卧晓，scrollEnabled默認為yes贞远，所以大多數(shù)情況下，計算方式還是adjustedContentInset = safeAreaInset + contentInset.
UIScrollViewContentInsetAdjustmentNever:
adjustedContentInset = contentInset
UIScrollViewContentInsetAdjustmentAlways:
adjustedContentInset = safeAreaInset + contentInset

iOS中的安全區(qū)與`additionalSafeAreaInsets`

在http://www.reibang.com/p/efbc8619d56b中提到:

在iOS 11以后 Controller的automaticallyAdjustsScrollViewInsets屬性被廢棄了瓢捉，所以當tableView超出安全區(qū)域時系統(tǒng)自動調(diào)整了SafeAreaInsets值频丘，進而影響adjustedContentInset值，在iOS 11中決定tableView的內(nèi)容與邊緣距離的是adjustedContentInset屬性泡态，而不是contentInset搂漠。adjustedContentInset的計算方式見本文第二部分內(nèi)容。因為系統(tǒng)對adjustedContentInset值進行了調(diào)整某弦，所以導致tableView的內(nèi)容到邊緣的距離發(fā)生了變化桐汤，導致tableView下移了20pt（statusbar高度）或64pt（navigationbar高度）。

如果你的APP中使用的是自定義的navigationbar靶壮，隱藏掉系統(tǒng)的navigationbar怔毛，并且tableView的frame為(0,0,SCREEN_WIDTH, SCREEN_HEIGHT)開始，那么系統(tǒng)會自動調(diào)整SafeAreaInsets值為(20,0,0,0)亮钦，如果使用了系統(tǒng)的navigationbar馆截，那么SafeAreaInsets值為(64,0,0,0)，如果也使用了系統(tǒng)的tabbar蜂莉，那么SafeAreaInsets值為(64,0,49,0)蜡娶。關于什么情況下會發(fā)生內(nèi)容下移的問題，本文第三部分有介紹映穗。

image.png

在iOS7中Apple引入的UIViewController的topLayoutGuide和bottomLayoutGuide屬性, 他們可以讓我們創(chuàng)建約束已避免內(nèi)容被UIKit的橫條, 狀態(tài)欄, 導航或者標簽欄覆蓋, 現(xiàn)在在iOS11中全部被被廢棄, 并且由安全區(qū)替代.

viewController在iOS11中添加了一個新的屬性additionalSafeAreaInsets, 通過該屬性, 我們可以規(guī)定我們自己的safe ares insets, 最終系統(tǒng)根據(jù)我們設置的additionalSafeAreaInsets 以及 adjustedContentInset, 系統(tǒng)會計算出最終的 safe area.

注意: 如果viewController是在navigationController中, 那么應該先修改NavigationController的additionalSafeAreaInsets, 然后再改變viewController的additionalSafeAreaInsets.

建議仔細讀一下下面的參考資料, 騰訊 bugly 寫的文章非常棒

參考資料

iOS 11 安全區(qū)域適配總結
 適配iOS11--contentInsetAdjustmentBehavior

iOS中safe area對scrollView的內(nèi)容偏移產(chǎn)生的影響(iOS11的適配問題)

scrollview的幾個關鍵屬性

scrollView關鍵屬性的實踐(一)

scrollView關鍵屬性的實踐(二)

iOS11以后, contentInsetAdjustmentBehavior與adjustedContentInset的關系

iOS中的安全區(qū)與additionalSafeAreaInsets

參考資料

iOS11以后, `contentInsetAdjustmentBehavior`與`adjustedContentInset`的關系

iOS中的安全區(qū)與`additionalSafeAreaInsets`