相册拾取器UIImagePickerController

UIImagePickerController概述：
UIImagePickerController 类是获取选择图片和视频的用户接口。我们可以用这个controller选择我们所需要的图片和视频。对于这个类来说比较特殊，我们不能够任意定制，也不可以继承生成子类。
我们在用UIImagePickerController类的时候，只需要调用用代码实现其在什么位置显示和开始，当然我们之后可以选择所需的图片和影片，或者也可以不选择点击取消即可。
但是在我们调用接口之前，我们需要确认：

• 一：当前设备是否支持使用UIImagePickerController，这个时候我们需要调用isSourceTypeAvailable:方法判断。

• 二：查看符合的媒体类型（图片或者视频），这个时候我们调用availableMediaTypesForSourceType: 方法判断。
  同时使用UIImagePickerController时，我们需要UIImagePickerControllerDelegate协议代理实现一些特定时间特定的动作。在调用摄像头的时候我们可以选择使用闪光灯，但是默认条件下对视频有10分钟的限制，需要用videoMaximumDuration属性更改默认时间，

• 三：之后我们设定界面媒体的属性
  1：sourceType //从哪选取媒体

enum {

      UIImagePickerControllerSourceTypePhotoLibrary,

     UIImagePickerControllerSourceTypeCamera,
  
    UIImagePickerControllerSourceTypeSavedPhotosAlbum

};

typedef NSUInteger UIImagePickerControllerSourceType;

2: mediaTypes
mediaTypes用来确定再picker里显示那些类型的多媒体文件，图片？视频？

+ (NSArray *)availableMediaTypesForSourceType:(UIImagePickerControllerSourceType)sourceType

一共有三个可选的代理方法UIImagePickerControllerDelegate

  - (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary<NSString *,id> *)info;
  - (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker;
  - (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingImage:(UIImage *)image editingInfo:(nullable NSDictionary<NSString *,id> *)editingInfo NS_DEPRECATED_IOS(2_0, 3_0);

-(void) pick{
    
[imagePicker takePicture];

}

  - (IBAction)press:(id)sender {

    imagePicker = ［UIImagePickerController alloc] init];

    imagePicker.delegate = self;

     imagePicker.mediaTypes = [UIImagePickerController availableMediaTypesForSourceType:UIImagePickerControllerSourceTypeCamera];
    
imagePicker.sourceType = UIImagePickerControllerSourceTypeCamera;

    imagePicker.showsCameraControls = NO;


    UIView* view = ［UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 44)];

    view.backgroundColor = [UIColor redColor];
    
UIButton* button = ［UIButton alloc] initWithFrame:CGRectMake(0, 0, 40, 40)];

    button.backgroundColor = [UIColor blueColor];
    
[button addTarget:self action:@selector(pick) forControlEvents:UIControlEventTouchUpInside];
    
[view addSubview:button];

CGRect newFrame = CGRectMake(0.0,436,320,44);
view.frame = newFrame;

    imagePicker.cameraOverlayView = view;

    [self presentModalViewController:imagePicker animated:YES];

}

-(void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{

    if (［info objectForKey:UIImagePickerControllerMediaType] isEqualToString:(NSString*)kUTTypeImage]) {

      UIImage* image = [info objectForKey:UIImagePickerControllerOriginalImage];
UIImageWriteToSavedPhotosAlbum(image, self, @selector(image:didFinishSavingWithError:contextInfo:), nil);
      
} else if (［info objectForKey:UIImagePickerControllerMediaType] isEqualToString:(NSString*)kUTTypeMovie]) {
      NSString* path = ［info objectForKey:UIImagePickerControllerMediaURL] path];
   UISaveVideoAtPathToSavedPhotosAlbum(path, self, @selector(video:didFinishSavingWithError:contextInfo:), nil);
    
}

  [picker dismissModalViewControllerAnimated:YES];

}

-(void)imagePickerControllerDidCancel:(UIImagePickerController *)picker
{
    
[picker dismissModalViewControllerAnimated:YES];

}