React Native --- Native 调用 JS 之

之前项目中iOSNative 需要主动给JS 发送事件的时候一直使用的是下面这种方式：

[self.bridge.eventDispatcher sendAppEventWithName:@"QRCodeWithPhoto" body:@{
                                                                                @"scanResult":scandResult,
                                                                                @"stateCode":@(self.stateCode),
                                                                                }];

这种方式虽然还可以用，但是后面一直会有个黄色的警告，提示该方法已经被遗弃，可以使用RCTEventEmitter代替。为了后面项目的稳定，所以决定使用新的API 去实现该功能。不过网上对于RCTEventEmitter的资料实在太少，react native 的官网文档上对于native 给 JS 发送事件使用的还是上面那种被遗弃的方法。所以就按照网上查找的一些英文资料进行尝试。OC 层的话还是定义一个类，继承自 RCTEventEmitter：

#import "RCTEventEmitter.h"
#import "RCTBridge.h"
@interface NativeModule : RCTEventEmitter<RCTBridgeModule>

@end

.m文件

#import "NativeModule.h"
#import "AppDelegate.h"
@interface NativeModule()<UINavigationControllerDelegate,UIImagePickerControllerDelegate>
@property (nonatomic ,strong) UIViewController * showViewController;
@property (nonatomic ,assign) int  stateCode;   // 状态码，0:代表获取二维码成功，-1:代表失败或者没有二维码
@end
@implementation NativeModule
@synthesize bridge = _bridge;
RCT_EXPORT_MODULE()

- (NSArray<NSString *> *)supportedEvents
{
  return @[@"QRCodeFromPhoto"];  // 这里注意要和  [self sendEventWithName:@"QRCodeFromPhoto" body:@{ @"scanResult":scandResult, @"stateCode":@(self.stateCode), }]; 里面发送的事件名字一致，不然JS 端不会识别
}

RCT_EXPORT_METHOD(QRCode)
{
  UIImagePickerController * imagePicker = [[UIImagePickerController alloc]init];
  imagePicker.delegate = self;
  imagePicker.allowsEditing = YES;  //设置选中的照片可被编辑（设置的话点照片会进入大图预览界面，二维码功能不需要进入大图，所以注释掉）(这里设置为禁用的话虽然可以不进入大图预览编辑界面，但是会导致手机拍的照片不能识别（远距离拍的可以识别，近距离的不可以识别）)
  // 将来源设置为相册
  /**
   UIImagePickerControllerSourceTypePhotoLibrary,相册
   UIImagePickerControllerSourceTypeCamera,相机
   UIImagePickerControllerSourceTypeSavedPhotosAlbum,照片库
   */
  imagePicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
  [[self getShowViewController] presentViewController:imagePicker animated:YES completion:nil];
}

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary<NSString *,id> *)info
{
  UIImage * image = info[UIImagePickerControllerOriginalImage];
  // 初始化一个检测器
  CIDetector * detector = [CIDetector detectorOfType:CIDetectorTypeQRCode context:nil options:@{ CIDetectorAccuracy : CIDetectorAccuracyHigh }];
  [picker dismissViewControllerAnimated:YES completion:^{
    //设置数组，放置识别完之后的数据
    NSArray * resultArray = [detector featuresInImage:[CIImage imageWithData:UIImagePNGRepresentation(image)]];
    NSString * scandResult;
    //判断是否有数据（即是否是二维码）
    if (resultArray.count >= 1) {
      //取第一个元素就是二维码所存放的文本信息
      CIQRCodeFeature * feature = resultArray[0];
      scandResult = feature.messageString;
      self.stateCode = 0;
    }else
    {
      self.stateCode = -1;
      scandResult = @"该图片不包含二维码信息";
    }
    
    dispatch_async(dispatch_get_main_queue(), ^{
      [self sendEventWithName:@"QRCodeFromPhoto" body:@{
                                                        @"scanResult":scandResult,
                                                        @"stateCode":@(self.stateCode),
                                                        }];
    });
  
    
  }];
}

- (UIViewController *)getShowViewController
{
  AppDelegate *delegate = (AppDelegate *)[UIApplication sharedApplication].delegate;
  UIWindow * window = delegate.window;
  if ([window.rootViewController isKindOfClass:[UINavigationController class]]) {
    _showViewController = ((UINavigationController *)window.rootViewController).visibleViewController;
  }else if ([window.rootViewController isKindOfClass:[UITabBarController class]])
  {
    _showViewController = ((UITabBarController *)window.rootViewController).selectedViewController;
  }else
  {
    _showViewController = window.rootViewController;
  }
  return _showViewController;
}
@end

** JS 端调用的话 **

Paste_Image.png