iOS从手机相册选择一张照片并显示 Objective-C

要先给app设置访问相册的权限：

在项目的Info.plist文件里添加Privacy - Photo Library Usage Description权限

ViewController.h：

 #import <UIKit/UIKit.h>

 @interface ViewController : UIViewController
 {
     IBOutlet UIImageView *myImageView; //与ImageView视图关联
 }

 - (IBAction)buttonUp:(id)sender;  // 与一个Button关联

 @end

ViewController.m：

 #import "ViewController.h"

 @interface ViewController ()<UINavigationControllerDelegate,UIImagePickerControllerDelegate>//接口

 @end

 @implementation ViewController

 - (void)viewDidLoad {
     [super viewDidLoad];
     // Do any additional setup after loading the view, typically from a nib.
 }

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

 - (IBAction)buttonUp:(id)sender {
     //初始化UIImagePickerController类
     UIImagePickerController * picker = [[UIImagePickerController alloc] init];
     //判断数据来源为相册
     picker.sourceType = UIImagePickerControllerSourceTypeSavedPhotosAlbum;
     //设置代理
     picker.delegate = self;
     //打开相册
     [self presentViewController:picker animated:YES completion:nil];
 }

 //选择完成回调函数
 - (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary<NSString *,id> *)info{
     //获取图片
     UIImage *image = info[UIImagePickerControllerOriginalImage];
     [self dismissViewControllerAnimated:YES completion:nil];

     myImageView.image = image;
 }

 //用户取消选择
 - (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker{
     [self dismissViewControllerAnimated:YES completion:nil];
 }

 @end