iOS UIImagePickerController 录像和拍照-学习

最近在项目中，使用到相机，然后自己还不是很懂，因为自己接触的项目不是很常用到，但是现在接触的项目要做拍照上传头像功能，然后自己就在各个博客，搬了一些砖，但是还是不太理解，然后有时间自己就多多造一些轮子。然后先去官网看看，有没有demo，找到了很久以前的一个（传送门）。然后自己就Coding了一遍。

UIImagePickerController 的理解

1. 它是系统统一提供UI的，好像并不能修改它的UI，但是能控制它的显示View，通过cameraOverlayView属性

2.它的使用场景：拍照（不支持Live Photo）、录像、存取图片和video

3.简单使用：

 //1. 创建相机对象
    imagePicker = [[UIImagePickerController alloc] init];
    //2. 设置相机属性
    //2.1 来源： 有相机、 图库、相簿
    imagePicker.sourceType = UIImagePickerControllerSourceTypeCamera;
    //2.2 媒体类型：⚠️ 最好先设置 mediaTypes， 再设置 cameraCaptureMode,
    // kUTTypeImage (拍照,默认）
    // kUTTypeVideo（视频，但不带声音）
    // kUTTypeMovie（视频并带有声音）
    // kUTTypeLivePhoto （取得 Live Photo） > iOS 9
    imagePicker.mediaTypes  = [UIImagePickerController availableMediaTypesForSourceType:UIImagePickerControllerSourceTypeCamera];//[NSArray arrayWithObjects:(NSString *)kUTTypeImage, (NSString *)kUTTypeMovie, nil];
    //2.3 相机类型：录像或拍照
    imagePicker.cameraCaptureMode =  UIImagePickerControllerCameraCaptureModeVideo;
    imagePicker.allowsEditing = NO;// 允许图片编辑，拍照后可以简单的编辑图片
    imagePicker.showsCameraControls = YES;
    imagePicker.cameraViewTransform = CGAffineTransformIdentity;
    //2.4 设置摄像头 ：设置之前一定要先判断device 是否有后摄像头,不是每个device 都有前后摄像头的
    if ([UIImagePickerController isCameraDeviceAvailable:UIImagePickerControllerCameraDeviceRear]) {
        imagePicker.cameraDevice = UIImagePickerControllerCameraDeviceRear;
        if ([UIImagePickerController isCameraDeviceAvailable:UIImagePickerControllerCameraDeviceFront]) {
            cameraSelectionButton.alpha = 1.0;
            showCameraSelection = YES;
        }
    } else{
        imagePicker.cameraDevice = UIImagePickerControllerCameraDeviceFront;
    }
    //2.5 设置闪光灯 ：设置之前一定要先判断device 是否支持
    if ([UIImagePickerController isFlashAvailableForCameraDevice:imagePicker.cameraDevice]) {
        imagePicker.cameraFlashMode = UIImagePickerControllerCameraFlashModeOff;
        flashModeButton.alpha = 1.0;
        showFlashMode = YES;
    }
    imagePicker.videoMaximumDuration = 10;//10s 它默认最大录像时间是 10 minute = 600s
    //iOS 11 之后使用 videoExportPreset
    if (@available(iOS 11.0, *)) {
        imagePicker.videoExportPreset = AVAssetExportPreset1280x720;
    } else {
        // iOS 11 之前
         imagePicker.videoQuality = UIImagePickerControllerQualityType640x480;
    }
    
    // 代理
    imagePicker.delegate = self;
    //3. 显示
    [self presentViewController:imagePicker animated:YES completion:nil];

代理方法

不管是拍照录像，还是取照片都会走代理方法，存直接调用C语言方法

//前面两个只会调用一个☝️，两个都实现只会调用第二个
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingImage:(UIImage *)image editingInfo:(nullable NSDictionary<NSString *,id> *)editingInfo NS_DEPRECATED_IOS(2_0, 3_0);
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary<NSString *,id> *)info;
- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker;

去照片时，如果调用的是第二个方法，可以通过字典和相关的key，取得对应的图片或video。例如: UIImagePickerControllerOriginalImage
存图片和video 就比较简单，直接调用C语言函数：

//存图片，传path，和回调事件(判断是否存取成功)，不传也行
// Adds a photo to the saved photos album.  The optional completionSelector should have the form:
//  - (void)image:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo;//回调方法格式
UIKIT_EXTERN void UIImageWriteToSavedPhotosAlbum(UIImage *image, __nullable id completionTarget, __nullable SEL completionSelector, void * __nullable contextInfo) __TVOS_PROHIBITED;

//以下都是存video的，只是最后的方法，有回调事件(判断是否存取成功)
// Is a specific video eligible to be saved to the saved photos album? 
UIKIT_EXTERN BOOL UIVideoAtPathIsCompatibleWithSavedPhotosAlbum(NSString *videoPath) NS_AVAILABLE_IOS(3_1) __TVOS_PROHIBITED;

// Adds a video to the saved photos album. The optional completionSelector should have the form:
//  - (void)video:(NSString *)videoPath didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo;//回调方法格式
UIKIT_EXTERN void UISaveVideoAtPathToSavedPhotosAlbum(NSString *videoPath, __nullable id completionTarget, __nullable SEL completionSelector, void * __nullable contextInfo) NS_AVAILABLE_IOS(3_1) __TVOS_PROHIBITED;

这个东西比较简单。API 也比较简单。