效果

有一个头像按钮，点击进入相册，从相册中获取图片，更改按钮的图片为选取的图片

• 创建一个自定义UIButton按钮，并给一张图片

  - (void)createButton {

    //获取一张图片
    UIImage *image = [UIImage imageNamed:@"image.jpg"];`
    
    //给button一张图片
    [self.button setImage:image forState:UIControlStateNormal]; 
    
    self.button.frame = CGRectMake(100, 100, 100, 100);
    [self.view addSubview:self.button];
    
    
    //设置button的点击事件
     [self.button addTarget:self action:@selector(buttonAction:) forControlEvents:UIControlEventTouchUpInside];`
     
 } 

• button的点击事件

  - (void)buttonAction:(UIButton *)button{
  
    //创建一个 UIImagePickerController对象
    UIImagePickerController *picker = [[UIImagePickerController alloc] init];
    
    //是否允许用户编辑
    picker.allowsEditing = YES;
    
    //指定数据源
    //数据源是枚举值 一共有三种
    //UIImagePickerControllerSourceTypePhotoLibrary 从图库获取(所有图片)
    //UIImagePickerControllerSourceTypeCamera 使用相机拍摄获取
    //UIImagePickerControllerSourceTypeSavedPhotosAlbum 从相册获取(仅是相机拍摄的所有图片)
    picker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
    
    //指定代理人为self 
    //设置代理人之前要签订两个协议
    picker.delegate = self;
    
    
    //模态推入相册控制器
    [self presentViewController:picker animated:YES completion:^{
        
        
    }];
}

• 签订协议

//两个协议配套使用，缺一不可
   @interface ViewController ()<UINavigationControllerDelegate, UIImagePickerControllerDelegate>
 @end 

• 实现相册协议方法

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info{
    // 打印方法的形参info->观察结果是一个"字典"
    //    NSLog(@"%@", info);
    // 通过字典里面的UIImagePickerControllerOriginalImage找到获取的相册图片
    UIImage *image = [info objectForKey:@"UIImagePickerControllerOriginalImage"];
    // 将获取的图片设置为头像
    [self.button setImage:image forState:UIControlStateNormal];
    // 收回相册控制器
    [self dismissViewControllerAnimated:YES completion:^{
    }];
}