ios基础篇（一）—— UIImagePickerController类

作者: 方丈久居怡红院
来源: 51数据库
2021-07-03

UIImagePickerController简述：

UIImagePickerController 类是获取选择图片和视频的用户接口，我们可以用UIImagePickerController选择我们所需要的图片和视频。

注：UIImagePickerController不能够任意定制，也不可以继承生成子类。

一、UIImagePickerController的属性：

1、sourceType

设置UIImagePicker照片源类型，默认有3种。照片源类型

指定使用模式（照相机/相册／照片库）

enum {
UIImagePickerControllerSourceTypePhotoLibrary,? //照片库（通过同步存放的，用户不能删除）
UIImagePickerControllerSourceTypeCamera,? //照相机
UIImagePickerControllerSourceTypeSavedPhotosAlbum //保存的照片（通过拍照或者截屏保存的，用户可以删除）
};

2、BOOL?showsCameraControls

设置拍照时的下方的工具栏是否显示，如果需要自定义拍摄界面，则可把该工具栏隐藏。

3.?videoMaximumDuration

设置UIImagePicker的最大视频持续时间.默认10分钟

4.?+ availableMediaTypesForSourceType: // 指定源可用的媒体种类

?//获得相机模式下支持的媒体类型

NSArray* availableMediaTypes =
[UIImagePickerController?availableMediaTypesForSourceType:UIImagePickerControllerSourceTypeCamera];

3、BOOL?allowsEditing

设置当拍照完或在相册选完照片后，是否跳到编辑模式进行图片剪裁即是否允许编辑

showsCameraControls=Yes时才有效果。

[imagePicker setAllowsEditing:YES];

4、cameraDevice

使用的镜头（默认后置的）

判断设备是否支持前置摄像头／后置摄像头

enum {
???? UIImagePickerControllerCameraDeviceRear,
???? UIImagePickerControllerCameraDeviceFront
???? };

+ isCameraDeviceAvailable: // 摄像设备是否可用.
+ availableCaptureModesForCameraDevice: // 设备可用的选取模式

??cameraCaptureMode //相机捕获模式

5、cameraFlashMode

设置闪光灯模式??(默认自动)

?enum {
???? UIImagePickerControllerCameraFlashModeOff? = -1,
???? UIImagePickerControllerCameraFlashModeAuto = 0,
???? UIImagePickerControllerCameraFlashModeOn?? = 1
???? };

?+ isFlashAvailableForCameraDevice: // 是否有闪光能力

6、mediaTypes

设置相机支持的类型，拍照和录像

+ (NSArray *)availableMediaTypesForSourceType:(UIImagePickerControllerSourceType)sourceType

UIImageWriteToSavedPhotosAlbum保存图像,
UISaveVideoAtPathToSavedPhotosAlbum保存视频.
4.0后使用writeImageToSavedPhotosAlbum:metadata:completionBlock:保存元数据.

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

– imagePickerController:didFinishPickingMediaWithInfo: ?
– imagePickerControllerDidCancel: ?
– imagePickerController:didFinishPickingImage:editingInfo:?

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

info中包括选取的照片，视频的主要信息

NSString *const UIImagePickerControllerMediaType;???????选取的类型 public.image? public.movie
NSString *const UIImagePickerControllerOriginalImage;??? 修改前的UIImage object.
NSString *const UIImagePickerControllerEditedImage;????修改后的UIImage object.
NSString *const UIImagePickerControllerCropRect;原始图片的尺寸NSValue object containing a CGRect data type
NSString *const UIImagePickerControllerMediaURL;?????视频在文件系统中 的 NSURL地址

7、cameraViewTransform

设置拍摄时屏幕的view的transform属性，可以实现旋转，缩放功能

enum{

CGAffineTransformMakeRotation；

CGAffineTransformMakeScale；

}

二、UIImagePickerController回调方法：

1、成功获得相片或视频后的回调

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

 - (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info{
    //通过UIImagePickerControllerMediaType判断返回的是照片还是视频
      NSString* type = [info objectForKey:UIImagePickerControllerMediaType];
      //如果返回的type等于kUTTypeImage，代表返回的是照片,并且需要判断当前相机使用的sourcetype是拍照还是相册
      if ([type isEqualToString:(NSString*)kUTTypeImage]&&picker.sourceType==UIImagePickerControllerSourceTypeCamera) {
          //获取照片的原图
          UIImage* original = [info
  objectForKey:UIImagePickerControllerOriginalImage];
          //获取图片裁剪的图
         UIImage* edit = [info objectForKey:UIImagePickerControllerEditedImage];
         //获取图片裁剪后，剩下的图
         UIImage* crop = [info objectForKey:UIImagePickerControllerCropRect];
         //获取图片的url
         NSURL* url = [info objectForKey:UIImagePickerControllerMediaURL];
        //获取图片的metaData数据信息
         NSDictionary* metaData = [info objectForKey:UIImagePickerControllerMediaMetadata];
         //如果是拍照的照片，则需要手动保存到本地，系统不会自动保存拍照成功后的照片
         UIImageWriteToSavedPhotosAlbum(edit, self, @selector(image:didFinishSavingWithError:contextInfo:), nil);
     }else{
     
     }
     //模态方式退出uiimagepickercontroller
     [imagepicker dismissModalViewControllerAnimated:YES];
 }

2、取消照相机的回调

- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker；

 - (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker{
     //模态方式退出UIImagePickerController
    [imagePicker dismissModalViewControllerAnimated:YES];
}

UIImagePickerController小例子

UIImagePickerController的代理需要遵守这两个协议.<UIImagePickerControllerDelegate, UINavigationControllerDelegate>

#pragma mark 选择照片

- (void)selectPhoto{

????// 1. 首先判断照片源是否可用
????if?([UIImagePickerController?isSourceTypeAvailable:UIImagePickerControllerSourceTypePhotoLibrary]) {
????????// 0）实例化控制器
????????UIImagePickerController?*picker = [[UIImagePickerController?alloc]init];
????????// 1）设置照片源
????????[picker setSourceType:UIImagePickerControllerSourceTypePhotoLibrary];
????????// 2) 设置允许修改
????????[picker setAllowsEditing:YES];
????????// 3) 设置代理
????????[picker setDelegate:self];
????????// 4) 显示控制器
????????[self?presentViewController:picker animated:YES?completion:nil];

????} else?{
????????NSLog(@"照片源不可用");
????}
}

#pragma mark - imagePicker代理方法

- (void)imagePickerController:(UIImagePickerController?*)picker didFinishPickingMediaWithInfo:(NSDictionary?*)info{
????UIImage?*image = info[@"UIImagePickerControllerEditedImage"];
????[_imageButton?setImage:image forState:UIControlStateNormal];????
????// 关闭照片选择器
????[self?dismissViewControllerAnimated:YES?completion:nil];????
????// 需要将照片保存至应用程序沙箱，由于涉及到数据存储，同时与界面无关
????// 可以使用多线程来保存图像
????dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{?????
????????// 保存图像
????????// 1. 取图像路径
????????NSArray?*docs = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
????????NSString?*imagePath = [docs[0]stringByAppendingPathComponent:@"abc.png"];
???????// 2. 转换成NSData保存
????????NSData?*imageData = UIImagePNGRepresentation(image);
????????[imageData writeToFile:imagePath atomically:YES];
????});
}

UIImagePicker使用步骤:

????检查指定源是否可用. isSourceTypeAvailable:方法.
????检查可用媒体(视频还是只能是图片) availableMediaTypesForSourceType:方法.
????设置界面媒体属性mediaTypes property.
????显示界面使用presentViewController:animated:completion:方法.iPad中是popover形式.需要确保sourceType有效.
????相关操作,移除视图.

如果想创建一个完全自定义界面的image picker来浏览图片,使用?Assets Library Framework Reference中的类. (AV Foundation Programming Guide 中的?“Media Capture and Access to Camera” )

参考：https://www.jianshu.com/p/966a3b9a72be