适配只看三个参数:
1.渲染像素–屏幕截图的图片尺寸，单位px
2.逻辑像素–程序员开发所用尺寸，单位pt
3.倍率–渲染像素/逻辑像素，得到倍数关系。常见倍率@2x,@3xSafe Area（安全区）:
iOS 9以后加入了Safe Area概念，页面内容不能超出安全区（Safe Area），底部区域用于手势进入主屏或切换应用，如果将触发交互行为的按钮放在屏幕的底部，会破坏App操作体验。
iPhoneX和XR/XS/XS MAX安全区计算方式相同：
常用宏：
// 判断是否是ipad#define isPad ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPad)// 判断iPhone4系列#define kiPhone4 ([UIScreen instancesRespondToSelector:@selector(currentMode)] ? CGSizeEqualToSize(CGSizeMake(640, 960), [[UIScreen mainScreen] currentMode].size) && !isPad : NO)// 判断iPhone5系列#define kiPhone5 ([UIScreen instancesRespondToSelector:@selector(currentMode)] ? CGSizeEqualToSize(CGSizeMake(640, 1136), [[UIScreen mainScreen] currentMode].size) && !isPad : NO)// 判断iPhone6系列#define kiPhone6 ([UIScreen instancesRespondToSelector:@selector(currentMode)] ? CGSizeEqualToSize(CGSizeMake(750, 1334), [[UIScreen mainScreen] currentMode].size) && !isPad : NO)//判断iphone6+系列#define kiPhone6Plus ([UIScreen instancesRespondToSelector:@selector(currentMode)] ? CGSizeEqualToSize(CGSizeMake(1242, 2208), [[UIScreen mainScreen] currentMode].size) && !isPad : NO)// 判断iPhoneX#define IS_IPHONE_X ([UIScreen instancesRespondToSelector:@selector(currentMode)] ? CGSizeEqualToSize(CGSizeMake(1125, 2436), [[UIScreen mainScreen] currentMode].size) && !isPad : NO)// 判断iPHoneXr#define IS_IPHONE_Xr ([UIScreen instancesRespondToSelector:@selector(currentMode)] ? CGSizeEqualToSize(CGSizeMake(828, 1792), [[UIScreen mainScreen] currentMode].size) && !isPad : NO)// 判断iPhoneXs#define IS_IPHONE_Xs ([UIScreen instancesRespondToSelector:@selector(currentMode)] ? CGSizeEqualToSize(CGSizeMake(1125, 2436), [[UIScreen mainScreen] currentMode].size) && !isPad : NO)// 判断iPhoneXs Max#define IS_IPHONE_Xs_Max ([UIScreen instancesRespondToSelector:@selector(currentMode)] ? CGSizeEqualToSize(CGSizeMake(1242, 2688), [[UIScreen mainScreen] currentMode].size) && !isPad : NO)//状态栏高度#define Height_StatusBar ((IS_IPHONE_X == YES || IS_IPHONE_Xr == YES || IS_IPHONE_Xs == YES || IS_IPHONE_Xs_Max == YES) ? 44.0 : 20.0)//导航栏高度(包括状态栏)#define Height_NavBar ((IS_IPHONE_X == YES || IS_IPHONE_Xr == YES || IS_IPHONE_Xs == YES || IS_IPHONE_Xs_Max == YES) ? 88.0 : 64.0)//TabBar高度#define Height_TabBar ((IS_IPHONE_X == YES || IS_IPHONE_Xr == YES || IS_IPHONE_Xs == YES || IS_IPHONE_Xs_Max == YES) ? 83.0 : 49.0)//底部安全距离#define TabbarSafeBottomMargin ((IS_IPHONE_X == YES || IS_IPHONE_Xr == YES || IS_IPHONE_Xs == YES || IS_IPHONE_Xs_Max == YES) ? 34.f : 0.f)
