ios基础篇（一）—— UIImagePickerController类

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 = [infoobjectForKey: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urlNSURL* 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