Flutter 控制屏幕旋转的实现

最近需要做个平板的项目，然后需要直接横屏，有2种实现方式。

1, 随着屏幕旋转，布局自动调整。做横竖屏适配

2，强制屏幕横屏，不随着屏幕去调整

第一种方式这里就不做说明了。代码做适配就可以。 下面说一下第二种实现方式

Flutter 自带方式

flutter 为我们提供了方法来控制系统的横竖屏显示

 SystemChrome.setPreferredOrientations([
   DeviceOrientation.landscapeLeft,
   DeviceOrientation.landscapeRight,
   DeviceOrientation.portrAItUp,
   DeviceOrientation.portraitDown
  ]).then((_) {
  });

包含的方向类型。 ！！！！但是但是但是这个方法只适用于Android在iOS上没有效果，上网查资料有大神封装的 flutter插件orientation ,flutter插件auto_orientation 在iOS上都起不到效果，所以打算自己写一个原生文件与flutter进行通讯，实现屏幕旋转。也是笔者在查询资料之后做的一个整合和解释说明

iOS端实现屏幕旋转

创建iOS原生文件

创建iOS原生文件来实现交互，首先要创建个原生文件。命名为FlutterIOSDevicePlugin。 创建文件

创建一个命名为FlutterIOSDevicePlugin.h 和命名为FlutterIOSDevicePlugin.m文件，说明一下： FlutterIOSDevicePlugin.h文件选择图片里面的header File模块创建即可。

创建之后，一起看一下FlutterIOSDevicePlugin.h里面的代码

#ifndef FlutterIOSDevicePlugin_h
#define FlutterIOSDevicePlugin_h

#import <Flutter/Flutter.h>

@interface FlutterIOSDevicePlugin : NSObject<FlutterPlugin>
+ (void)registerWithRegistrar:(NSObject<FlutterPluginRegistrar>*)registrar flutterViewController:(FlutterViewController*) controller;
- (instancetype)newInstance:(NSObject<FlutterPluginRegistrar>*)registrar flutterViewController:(FlutterViewController*) controller;
@end
#endif /* FlutterIOSDevicePlugin_h */

这个不需要过多说明了看一下FlutterIOSDevicePlugin.m的代码

#import <Foundation/Foundation.h>
#import "FlutterIOSDevicePlugin.h"

@interface FlutterIOSDevicePlugin () {
  NSObject<FlutterPluginRegistrar> *_registrar;
  FlutterViewController *_controller;
}
@end

static NSString* const CHANNEL_NAME = @"flutter_ios_device";
static NSString* const METHOD_CHANGE_ORIENTATION = @"change_screen_orientation";
static NSString* const ORIENTATION_PORTRAIT_UP = @"portraitUp";
static NSString* const ORIENTATION_PORTRAIT_DOWN = @"portraitDown";
static NSString* const ORIENTATION_LANDSCAPE_LEFT = @"landscapeLeft";
static NSString* const ORIENTATION_LANDSCAPE_RIGHT = @"landscapeRight";

@implementation FlutterIOSDevicePlugin
+ (void)registerWithRegistrar:(NSObject<FlutterPluginRegistrar>*)registrar {
  FlutterMethodChannel* channel = [FlutterMethodChannel
                   methodChannelWithName:CHANNEL_NAME
                   binaryMessenger:[registrar messenger]];
  FlutterIOSDevicePlugin* instance = [[FlutterIOSDevicePlugin alloc] newInstance:registrar flutterViewController:nil];
  [registrar addMethodCallDelegate:instance channel:channel];
}

+ (void)registerWithRegistrar:(NSObject<FlutterPluginRegistrar>*)registrar flutterViewController:(FlutterViewController*) controller {
  FlutterMethodChannel* channel = [FlutterMethodChannel
                   methodChannelWithName:CHANNEL_NAME
                   binaryMessenger:[registrar messenger]];
  FlutterIOSDevicePlugin* instance = [[FlutterIOSDevicePlugin alloc] newInstance:registrar flutterViewController:controller];
  [registrar addMethodCallDelegate:instance channel:channel];
}

- (instancetype)newInstance:(NSObject<FlutterPluginRegistrar>*)registrar flutterViewController:(FlutterViewController*) controller{
  _registrar = registrar;
  _controller = controller;
  return self;
}

- (void)handleMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result {
  if ([METHOD_CHANGE_ORIENTATION isEqualToString:call.method]) {
    NSArray *arguments = call.arguments;
    NSString *orientation = arguments[0];
    NSNumber *index = [NSNumber numberWithInt: [call.arguments[0] intValue]];
    NSInteger iOSOrientation;
     if ([orientation isEqualToString:ORIENTATION_LANDSCAPE_LEFT]){
           iOSOrientation = UIDeviceOrientationLandscapeLeft;
         }else if([orientation isEqualToString:ORIENTATION_LANDSCAPE_RIGHT]){
           iOSOrientation = UIDeviceOrientationLandscapeRight;
         }else if ([orientation isEqualToString:ORIENTATION_PORTRAIT_DOWN]){
           iOSOrientation = UIDeviceOrientationPortraitUpsideDown;
         }else{
           iOSOrientation = UIDeviceOrientationPortrait;
         }

    [[UIDevice currentDevice] setValue:@(iOSOrientation) forKey:@"orientation"];
//    [[NSNotificationCenter defaultCenter] postNotificationName:@"FlutterIOSDevicePlugin" object:nil userInfo:@{@"orientationMask": index}];
//    [UIViewController attemptRotationToDeviceOrientation];

    result(nil);
  } else {
    result(FlutterMethodNotImplemented);
  }
}
@end

以上是全部的代码，其中尝试了用通知的方式去做屏幕旋转，后来发现其实没有那么麻烦，直接采用的是

[[UIDevice currentDevice] setValue:@(iOSOrientation) forKey:@"orientation"];

方式做的。其中遇到的问题：

问题1:iPhone手机上可以正常旋转，iPad上不行

这个问题主要原因是info。plist文件里面的iphone和ipad不一致，且勾选Requires full screen 即可

回到正轨哈

注册原生插件文件

iOS 工程种有个GeneratedPluginRegistrant.m文件，直接注册就可以了。 如果你项目引入了其他第三方插件，也是统一在这个地方注册的

#import "GeneratedPluginRegistrant.h"

#if __has_include(<auto_orientation/AutoOrientationPlugin.h>)
#import <auto_orientation/AutoOrientationPlugin.h>
#else
@import auto_orientation;
#endif

#if __has_include(<orientation/OrientationPlugin.h>)
#import <orientation/OrientationPlugin.h>
#else
@import orientation;
#endif
#import "FlutterIOSDevicePlugin.h"

@implementation GeneratedPluginRegistrant

+ (void)registerWithRegistry:(NSObject<FlutterPluginRegistry>*)registry {
 [AutoOrientationPlugin registerWithRegistrar:[registry registrarForPlugin:@"AutoOrientationPlugin"]];
 [OrientationPlugin registerWithRegistrar:[registry registrarForPlugin:@"OrientationPlugin"]];
//  [registry registrarForPlugin:@"FlutterIOSDevicePlugin"];
  

  [FlutterIOSDevicePlugin registerWithRegistrar: [registry registrarForPlugin:@"FlutterIOSDevicePlugin"]];
}

@end

代码中的这个片段是自己写的插件注册的方法，其他的AutoOrientationPlugin，OrientationPlugin是引用第三方插件自动生成的代码。

[FlutterIOSDevicePlugin registerWithRegistrar: [registry registrarForPlugin:@"FlutterIOSDevicePlugin"]];

AppDelegate文件中的设置

import UIKit
import Flutter



@UIApplicationMain
@objc class AppDelegate: FlutterAppDelegate {
 var orientationMask: UIInterfaceOrientationMask = .all;
  
 override func application(
  _ application: UIApplication,
  didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
 ) -> Bool {
  NotificationCenter.default.addObserver(self, selector: #selector(changeLandscape(center:)), name:NSNotification.Name(rawValue: "FlutterIOSDevicePlugin"), object: nil)
  GeneratedPluginRegistrant.register(with: self);
  return super.application(application, didFinishLaunchingWithOptions: launchOptions)
 }
  override func application(_ application: UIApplication, supportedInterfaceOrientationsFor window: UIWindow?) -> UIInterfaceOrientationMask {
    return orientationMask;
  }
  
  @objc func changeLandscape(center: Notification){
    let index: NSNumber = (center.userInfo?["orientationMask"] ?? 5) as! NSNumber
    var mask : UIInterfaceOrientationMask = .all
    Switch index {
    case 0:
      mask = .portrait
      break
    case 1:
      mask = .landscapeLeft
      break
    case 2:
      mask = .landscapeRight
      break
    case 3:
      mask = .portraitUpsideDown
      break
    case 4:
      mask = .landscape
      break
    case 5:
      mask = .all
      break
    case 6:
      mask = .allButUpsideDown
      break
    
    default:
      mask = .all
      break
    }
    orientationMask = mask;
    _ = application(UIApplication.shared, supportedInterfaceOrientationsFor: UIApplication.shared.keyWindow)
  }
}

其中changeLandscape方法是控制监听的事件的方法，目前没什么用。 主要代码是这一段，这个是在发出屏幕旋转的时候回调的方法，这里面设置的是全部的方向都可以。

  override func application(_ application: UIApplication, supportedInterfaceOrientationsFor window: UIWindow?) -> UIInterfaceOrientationMask {
    return orientationMask;
  }

问题2:程序不走该方法

具体原因是因为info.plist文件问题。参考上面设置就没问题

flutter 原生代码使用

这个地方是针对于iOS平台去做的区别。

MethodChannel _channel = const MethodChannel('flutter_ios_device');

@override
 void initState() {
  SystemChrome.setPreferredOrientations([
   DeviceOrientation.landscapeLeft,
   DeviceOrientation.landscapeRight,
   DeviceOrientation.portraitUp,
   DeviceOrientation.portraitDown
  ]).then((_) {
   if (Platform.isIOS) {
    this.changeScreenOrientation(DeviceOrientation.landscapeLeft);
   }
  });
  super.initState();
 }
 
Future<void> changeScreenOrientation(DeviceOrientation orientation) {
  String o;
  switch (orientation) {
   case DeviceOrientation.portraitUp:
    o = 'portraitUp';
    break;
   case DeviceOrientation.portraitDown:
    o = 'portraitDown';
    break;
   case DeviceOrientation.landscapeLeft:
    o = 'landscapeLeft';
    break;
   case DeviceOrientation.landscapeRight:
    o = 'landscapeRight';
    break;
  }
  return _channel.invokeMethod('change_screen_orientation', [o]);
 }

代码不用过多说明了， 有不了解的可以留言

问题3: 启动程序自动旋转

SystemChrome.setPreferredOrientations需要设置全部内容。不然会默认旋转。有点小坑，