iOS强制转屏

引言

遇到需要转屏的功能，查资料刚好看到一篇iOS强制横屏或强制竖屏，不过发现里面的方法有点太不可取，做了下修改。

为什么push或者pop后的viewController 不响应所有的 旋转方法？

这里是因为，根视图（rootController）不是你的viewController，你去监听肯定是没有的，这里你就需要监听根视图，比如说下面的例子中的nav。

BaseNavCtl ---- 这代码里，是为了让MultiQualityViewController横屏，这里就举这一个栗子

#import <UIKit/UIKit.h>

@interface BaseNavCtl : UINavigationController

@end

BaseNavCtl .m

    //
    //  BaseNavCtl.m
    //  MGMediaDemo
    //
    //  Created by ciome on 2017/4/5.
    //  Copyright © 2017年 MiGu. All rights reserved.
    //
    
    #import "BaseNavCtl.h"
    #import "MultiQualityViewController.h"
    
    @interface BaseNavCtl ()
    
    
    @end
    
    @implementation BaseNavCtl
    
    - (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}



- (UIInterfaceOrientationMask)supportedInterfaceOrientations {
    
    // 获取topCtl
    UIViewController  *ctl = self.topViewController;
    // 进行后续区分
    if([ctl isKindOfClass:[MultiQualityViewController class]]){
        
        return UIInterfaceOrientationMaskLandscape;
    }
    else {
        
        return UIInterfaceOrientationMaskAll;
    }
}

- (BOOL)shouldAutorotate
{
    return true;
}

 - (void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated
{
    // 获取topCtl
    UIViewController  *ctl = viewController;
    // 在进入之前强制旋转设备
    if([ctl isKindOfClass:[MultiQualityViewController class]]){
        
        [self interfaceOrientation:UIInterfaceOrientationLandscapeRight];
    }
    [super pushViewController:viewController animated:animated];
}



// 强制转屏 
- (void)interfaceOrientation:(UIInterfaceOrientation)orientation
{
    if ([[UIDevice currentDevice] respondsToSelector:@selector(setOrientation:)]) {
        SEL selector  = NSSelectorFromString(@"setOrientation:");
        NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:[UIDevice instanceMethodSignatureForSelector:selector]];
        [invocation setSelector:selector];
        [invocation setTarget:[UIDevice currentDevice]];
        int val = orientation;
        // 从2开始是因为0 1 两个参数已经被selector和target占用
        [invocation setArgument:&val atIndex:2];
        [invocation invoke];
    }
}


/*
#pragma mark - Navigation

// In a storyboard-based application, you will often want to do a little preparation before navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    // Get the new view controller using [segue destinationViewController].
    // Pass the selected object to the new view controller.
}
*/

@end

AppDelegate --- BaseNavCtl成为rootController

self.window= [[UIWindow alloc]initWithFrame:[[UIScreen mainScreen]bounds]];
BaseNavCtl *navigationController = [[BaseNavCtl alloc]initWithRootViewController:[[DemoMainViewController alloc]init]];
self.viewController= navigationController;
self.window.rootViewController=self.viewController;
[self.window makeKeyAndVisible];

为什么这样写

这样写的好处是，可以把整个APP内的视图方向管理，都集中在baseNavCtl这个类里面；当然，这样也必然增加了每次匹配的消耗，但由于每次nav只有一个topViewCtl ，所以可以做唯一判别减少匹配消耗，这里就不贴代码了。