首先，在Info.plist文件中添加下面两个key，根据app具体需求设置相应的文案：
Privacy - Camera Usage Description
Privacy - Photo Library Usage Description

Info.plist.png

在main.storyBoard里拖一个imageView并连线，用来显示拍摄或从相册中选取的图片：

main.storyBoard.png

调用系统相机，引入头文件：

#import <AVFoundation/AVFoundation.h>

调用系统相册，引入头文件：

#import <AssetsLibrary/AssetsLibrary.h>
#import <Photos/Photos.h>

遵循代理，设置全局变量并初始化：

@interface ViewController ()<UINavigationControllerDelegate, UIImagePickerControllerDelegate>

@property (weak, nonatomic) IBOutlet UIImageView *avatar;

@property (nonatomic, strong) UIImagePickerController *imagePickerController;

- (void)viewDidLoad {
    [super viewDidLoad];

    //为imageView添加点击事件：
    self.avatar.userInteractionEnabled = YES;
    UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapAvatar)];
    [self.avatar addGestureRecognizer:tap];
}

- (UIImagePickerController *)imagePickerController {
    if (_imagePickerController == nil) {
        _imagePickerController = [[UIImagePickerController alloc] init];
        _imagePickerController.delegate = self; //delegate遵循了两个代理
        _imagePickerController.allowsEditing = YES;
    }
    return _imagePickerController;
}

点击imageView，弹出系统弹框：

- (void)tapAvatar {
    UIAlertController *alert = [UIAlertController alertControllerWithTitle:nil message:nil preferredStyle:UIAlertControllerStyleActionSheet];

    UIAlertAction *camera = [UIAlertAction actionWithTitle:@"Camera" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
        [self checkCameraPermission];//检查相机权限
    }];
    UIAlertAction *album = [UIAlertAction actionWithTitle:@"Album" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
         [self checkAlbumPermission];//检查相册权限
    }];
    UIAlertAction *cancel = [UIAlertAction actionWithTitle:@"Cancel" style:UIAlertActionStyleCancel handler:^(UIAlertAction * action) {
        [self dismissViewControllerAnimated:YES completion:nil];
    }];

    [alert addAction:camera];
    [alert addAction:album];
    [alert addAction:cancel];

    [self presentViewController:alert animated:YES completion:nil];
}

系统弹框.PNG

#pragma mark - Camera
- (void)checkCameraPermission {
    AVAuthorizationStatus status = [AVCaptureDevice authorizationStatusForMediaType:AVMediaTypeVideo];
    if (status == AVAuthorizationStatusNotDetermined) {
        [AVCaptureDevice requestAccessForMediaType:AVMediaTypeVideo completionHandler:^(BOOL granted) {
            if (granted) {
                [self takePhoto];
            }
        }];
    } else if (status == AVAuthorizationStatusDenied || status == AVAuthorizationStatusRestricted) {
        [self alertCamear];
    } else {
        [self takePhoto];
    }
}

- (void)takePhoto {
    //判断相机是否可用，防止模拟器点击【相机】导致崩溃
    if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) {
        self.imagePickerController.sourceType = UIImagePickerControllerSourceTypeCamera;
        [self presentViewController:self.imagePickerController animated:YES completion:^{

        }];
    } else {
        NSLog(@"不能使用模拟器进行拍照");
    }
}

#pragma mark - Album
- (void)checkAlbumPermission {
    PHAuthorizationStatus status = [PHPhotoLibrary authorizationStatus];
    if (status == PHAuthorizationStatusNotDetermined) {
        [PHPhotoLibrary requestAuthorization:^(PHAuthorizationStatus status) {
            dispatch_async(dispatch_get_main_queue(), ^{
                if (status == PHAuthorizationStatusAuthorized) {
                    [self selectAlbum];
                }
            });
        }];
    } else if (status == PHAuthorizationStatusDenied || status == PHAuthorizationStatusRestricted) {
        [self alertAlbum];
    } else {
        [self selectAlbum];
    }
}

- (void)selectAlbum {
    //判断相册是否可用
    if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypePhotoLibrary]) {
        self.imagePickerController.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
        [self presentViewController:self.imagePickerController animated:YES completion:^{

        }];
    }
}

- (void)alertAlbum {
    UIAlertController *alert = [UIAlertController alertControllerWithTitle:nil message:@"请在设置中打开相册" preferredStyle:UIAlertControllerStyleAlert];
    UIAlertAction *cancel = [UIAlertAction actionWithTitle:@"Cancel" style:UIAlertActionStyleCancel handler:^(UIAlertAction * _Nonnull action) {
        [self dismissViewControllerAnimated:YES completion:nil];
    }];
    [alert addAction:cancel];
    [self presentViewController:alert animated:YES completion:nil];
}

UIImagePickerControllerDelegate代理方法：

#pragma mark - UIImagePickerControllerDelegate
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary<UIImagePickerControllerInfoKey,id> *)info {
    [picker dismissViewControllerAnimated:YES completion:nil];
    UIImage *image = [info valueForKey:UIImagePickerControllerEditedImage];
    self.avatar.image = image;
}

OnePiece.PNG