引言

UIImagePickerController确实非常强大，但是雨MPMoviePlayerController类似，由于它的高度封装性，要进行某些自定义工作就比较复杂了。例如要做出一款类似于美颜相机的拍照界面就比较难以实现了，此时就可以考虑使用AVFoundation来实现。AVFoundation中提供了很多现成的播放器和录音机，但是事实上他还有更加底层的内容可以供开发者使用。因为AVFoundation中抽了很多和底层输入，输出设备打交道的类，依靠这些类开发人员面对的不再是封装好的音频播放器AVAudioPlayer、录音机（AVAudioRecorder）、视频（包括音频）播放器AVPlayer，而是输入设备（例如麦克风、摄像头）、输出设备（图片、视频）等。首先了解一下使用AVFoundation做拍照和视频录制开发用到的相关类：

• AVCaptureSession：媒体（音、视频）捕获会话，负责把捕获的音视频数据输出到输出设备中。一个AVCaptureSession可以有多个输入输出：如图：

AVCaptureSession可以有多个输入输出

• AVCaptureDevice：输入设备，包括麦克风、摄像头，通过该对象可以设置物理设备的一些属性（例如相机聚焦、白平衡等）。
• AVCaptureDeviceInput：设备输入数据管理对象，可以根据AVCaptureDevice创建对应的AVCaptureDeviceInput对象，该对象将会被添加到AVCaptureSession中管理。
• AVCaptureOutput：输出数据管理对象，用于接收各类输出数据，通常使用对应的子类AVCaptureAudioDataOutput、AVCaptureStillImageOutput、AVCaptureVideoDataOutput、AVCaptureFileOutput，该对象将会被添加到AVCaptureSession中管理。注意：前面几个对象的输出数据都是NSData类型，而AVCaptureFileOutput代表数据以文件形式输出，类似的，AVCcaptureFileOutput也不会直接创建使用，通常会使用其子类：AVCaptureAudioFileOutput、AVCaptureMovieFileOutput。当把一个输入或者输出添加到AVCaptureSession之后AVCaptureSession就会在所有相符的输入、输出设备之间建立连接（AVCaptionConnection）：

输入、输出设备之间建立连接

• AVCaptureVideoPreviewLayer：相机拍摄预览图层，是CALayer的子类，使用该对象可以实时查看拍照或视频录制效果，创建该对象需要指定对应的AVCaptureSession对象。

使用AVFoundation拍照和录制视频的一般步骤如下：

• 创建AVCaptureSession对象。
• 使用AVCaptureDevice的静态方法获得需要使用的设备，例如拍照和录像就需要获得摄像头设备，录音就要获得麦克风设备。
• 利用输入设备AVCaptureDevice初始化AVCaptureDeviceInput对象。
• 初始化输出数据管理对象，如果要拍照就初始化AVCaptureStillImageOutput对象；如果拍摄视频就初始化AVCaptureMovieFileOutput对象。
• 将数据输入对象AVCaptureDeviceInput、数据输出对象AVCaptureOutput添加到媒体会话管理对象AVCaptureSession中。
• 创建视频预览图层AVCaptureVideoPreviewLayer并指定媒体会话，添加图层到显示容器中，调用AVCaptureSession的startRuning方法开始捕获。
• 将捕获的音频或视频数据输出到指定文件。

下面看一下如何使用AVFoundation实现一个拍照程序，在这个程序中将实现摄像头预览、切换前后摄像头、闪光灯设置、对焦、拍照保存等功能。应用大致效果如下：

#import "AVCostomAVViewController.h"
#import <AVFoundation/AVFoundation.h>
#import <AssetsLibrary/AssetsLibrary.h>


#define ScreenWith     [UIScreen mainScreen].bounds.size.width
#define ScreenHeight   [UIScreen mainScreen].bounds.size.height

typedef void(^PropertyChangeBlock) (AVCaptureDevice * captureDevice);

@interface AVCostomAVViewController ()<AVCaptureFileOutputRecordingDelegate>//视频文件输出代理
//负责输入和输出设备之间的数据传输
@property (nonatomic, strong) AVCaptureSession * captureSession;
//负责从AVCaptureDevice获得输入数据
@property (nonatomic, strong) AVCaptureDeviceInput * captureDeviceInput;
//照片输出流
@property (nonatomic, strong) AVCaptureStillImageOutput * captureStillImageOutput;
//视频输出流
@property (nonatomic, strong) AVCaptureMovieFileOutput * captureMovieFileOutPut;
@property (assign,nonatomic) UIBackgroundTaskIdentifier backgroundTaskIdentifier;//后台任务标识

//相机拍摄预览图层
@property (nonatomic, strong) AVCaptureVideoPreviewLayer * captureVideoPreviewLayer;
@property (nonatomic, strong) UIView * contentView;
//拍照按钮
@property (nonatomic, strong) UIButton * takeButton;
//视频录制按钮
@property (nonatomic, strong) UIButton * videoButton;
//自动闪光灯按钮
@property (nonatomic, strong) UIButton * flashAutoButton;
//打开闪光灯按钮
@property (nonatomic, strong) UIButton * flashOnButton;
//关闭闪光灯按钮
@property (nonatomic, strong) UIButton * flashOffButton;
//切换前后摄像头
@property (nonatomic, strong) UIButton * exchangeCamera;
//聚焦光标
@property (nonatomic, strong) UIImageView * focusCursor;

@end

@implementation AVCostomAVViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    self.view.backgroundColor = [UIColor whiteColor];
    self.title = @"自定义拍照和视频录制控件";
    
    [self setupUI];
    
    [self initCamera];
    
    [self.captureSession startRunning];

}

- (void)viewDidAppear:(BOOL)animated{
    [super viewDidAppear:animated];
}

- (void)viewDidDisappear:(BOOL)animated{
    [super viewDidDisappear:animated];
    [self.captureSession stopRunning];
}

- (void)dealloc{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

#pragma mark - 摄像头初始化
- (void)initCamera{
    //初始化会话
    _captureSession = [[AVCaptureSession alloc] init];
    //设置分辨率
    if ([_captureSession canSetSessionPreset:AVCaptureSessionPreset1280x720]) {
        _captureSession.sessionPreset=AVCaptureSessionPreset1280x720;
    }
    //获得输入设备
    AVCaptureDevice * captureDevice = [self getCameraDeviceWithPosition:AVCaptureDevicePositionBack];
    if (!captureDevice) {
        NSLog(@"取得后置摄像头时出现问题。");
        return;
    }
    
    NSError * error = nil;
    
    //添加一个音频输入设备
    AVCaptureDevice * audioCaptureDevice = [[AVCaptureDevice devicesWithMediaType:AVMediaTypeAudio] firstObject];
    AVCaptureDeviceInput * audioCaptureDeviceInput = [[AVCaptureDeviceInput alloc] initWithDevice:audioCaptureDevice error:&error];
    if (error) {
        NSLog(@"获得设备输入对象时出错，错误原因：%@",error.localizedDescription);
        return;
    }
    
    _captureMovieFileOutPut = [[AVCaptureMovieFileOutput alloc] init];
    
    //根据输入设备初始化设备输入对象，用于获得输入数据
    _captureDeviceInput = [[AVCaptureDeviceInput alloc]initWithDevice:captureDevice error:&error];
    if (error) {
        NSLog(@"取得设备输入对象时出错，错误原因：%@",error.localizedDescription);
        return;
    }
    //初始化设备输出对象，用于获得输出数据
    _captureStillImageOutput = [[AVCaptureStillImageOutput alloc] init];
    NSDictionary * outputSettings = @{AVVideoCodecKey:AVVideoCodecJPEG};
    //输出设置
    [_captureStillImageOutput setOutputSettings:outputSettings];
    
    //将设备输入添加到会话中
    if ([_captureSession canAddInput:_captureDeviceInput]) {
        [_captureSession addInput:_captureDeviceInput];
        [_captureSession addInput:audioCaptureDeviceInput];
        AVCaptureConnection * captureConnection = [_captureMovieFileOutPut connectionWithMediaType:AVMediaTypeVideo];
        ;
        if ([captureConnection isVideoStabilizationSupported]) {
            captureConnection.preferredVideoStabilizationMode= AVCaptureVideoStabilizationModeAuto;
        }
    }
    
    //将设输出添加到会话中
    if ([_captureSession canAddOutput:_captureStillImageOutput]) {
        [_captureSession addOutput:_captureStillImageOutput];
    }
    
    if ([_captureSession canAddOutput:_captureMovieFileOutPut]) {
        [_captureSession addOutput:_captureMovieFileOutPut];
    }
    
    //创建视频预览层，用于实时展示摄像头状态
    _captureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc]initWithSession:self.captureSession];
    
    CALayer * layer = self.contentView.layer;
    layer.masksToBounds = YES;
    
    _captureVideoPreviewLayer.frame = layer.bounds;
    //填充模式
    _captureVideoPreviewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
    
    //将视频预览层添加到界面中
    [layer insertSublayer:_captureVideoPreviewLayer below:self.focusCursor.layer];
    
    [self addNotificationToCaptureDevice:captureDevice];
    [self addGenstureRecognizer];
    [self setFlashModeButtonStatus];
}

#pragma mark - 视频输出代理
-(void)captureOutput:(AVCaptureFileOutput *)captureOutput didStartRecordingToOutputFileAtURL:(NSURL *)fileURL fromConnections:(NSArray *)connections{
    NSLog(@"开始录制...");
}
-(void)captureOutput:(AVCaptureFileOutput *)captureOutput didFinishRecordingToOutputFileAtURL:(NSURL *)outputFileURL fromConnections:(NSArray *)connections error:(NSError *)error{
    NSLog(@"视频录制完成.");
    //视频录入完成之后在后台将视频存储到相簿
  //  self.enableRotation=YES;
    UIBackgroundTaskIdentifier lastBackgroundTaskIdentifier=self.backgroundTaskIdentifier;
    self.backgroundTaskIdentifier=UIBackgroundTaskInvalid;
    ALAssetsLibrary *assetsLibrary=[[ALAssetsLibrary alloc]init];
    [assetsLibrary writeVideoAtPathToSavedPhotosAlbum:outputFileURL completionBlock:^(NSURL *assetURL, NSError *error) {
        if (error) {
            NSLog(@"保存视频到相簿过程中发生错误，错误信息：%@",error.localizedDescription);
        }
        if (lastBackgroundTaskIdentifier!=UIBackgroundTaskInvalid) {
            [[UIApplication sharedApplication] endBackgroundTask:lastBackgroundTaskIdentifier];
        }
        NSLog(@"成功保存视频到相簿.");
    }];
    
}

#pragma mark - 摄像头相关
//  给输入设备添加通知
-(void)addNotificationToCaptureDevice:(AVCaptureDevice *)captureDevice{
    //注意添加区域改变捕获通知必须首先设置设备允许捕获
    [self changeDeviceProperty:^(AVCaptureDevice *captureDevice) {
        captureDevice.subjectAreaChangeMonitoringEnabled=YES;
    }];
    NSNotificationCenter *notificationCenter= [NSNotificationCenter defaultCenter];
    //捕获区域发生改变
    [notificationCenter addObserver:self selector:@selector(areaChange:) name:AVCaptureDeviceSubjectAreaDidChangeNotification object:captureDevice];
}

-(void)removeNotificationFromCaptureDevice:(AVCaptureDevice *)captureDevice{
    NSNotificationCenter *notificationCenter= [NSNotificationCenter defaultCenter];
    [notificationCenter removeObserver:self name:AVCaptureDeviceSubjectAreaDidChangeNotification object:captureDevice];
}

-(void)removeNotification{
    NSNotificationCenter *notificationCenter= [NSNotificationCenter defaultCenter];
    [notificationCenter removeObserver:self];
}

-(void)addNotificationToCaptureSession:(AVCaptureSession *)captureSession{
    NSNotificationCenter *notificationCenter= [NSNotificationCenter defaultCenter];
    //会话出错
    [notificationCenter addObserver:self selector:@selector(sessionRuntimeError:) name:AVCaptureSessionRuntimeErrorNotification object:captureSession];
}

//屏幕旋转时调整视频预览图层的方向
-(void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration{
    AVCaptureConnection *captureConnection=[self.captureVideoPreviewLayer connection];
    captureConnection.videoOrientation=(AVCaptureVideoOrientation)toInterfaceOrientation;
}
//旋转后重新设置大小
-(void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation{
    _captureVideoPreviewLayer.frame=self.contentView.bounds;
}

//获取指定位置的摄像头
- (AVCaptureDevice *)getCameraDeviceWithPosition:(AVCaptureDevicePosition) positon{

    NSArray * cameras = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
    for (AVCaptureDevice * camera in cameras) {
        if ([camera position] == positon) {
            return camera;
        }
    }
    return nil;
}

//属性改变操作
- (void)changeDeviceProperty:(PropertyChangeBlock ) propertyChange{
   
    AVCaptureDevice * captureDevice = [self.captureDeviceInput device];
    NSError * error;
    //注意改变设备属性前一定要首先调用lockForConfiguration:调用完之后使用unlockForConfiguration方法解锁
    if ([captureDevice lockForConfiguration:&error]) {
      
        propertyChange(captureDevice);
        [captureDevice unlockForConfiguration];
        
    } else {
        
        NSLog(@"设置设备属性过程发生错误，错误信息：%@", error.localizedDescription);
    }
}

//设置闪光灯模式
- (void)setFlashMode:(AVCaptureFlashMode ) flashMode{
    [self changeDeviceProperty:^(AVCaptureDevice *captureDevice) {
        if ([captureDevice isFlashModeSupported:flashMode]) {
            [captureDevice setFlashMode:flashMode];
        }
    }];
}

//聚焦模式
- (void)setFocusMode:(AVCaptureFocusMode) focusMode{
    [self changeDeviceProperty:^(AVCaptureDevice *captureDevice) {
        if ([captureDevice isFocusModeSupported:focusMode]) {
            [captureDevice setFocusMode:focusMode];
        }
    }];
}

//设置曝光模式
- (void)setExposureMode:(AVCaptureExposureMode) exposureMode{
    [self changeDeviceProperty:^(AVCaptureDevice *captureDevice) {
        if ([captureDevice isExposureModeSupported:exposureMode]) {
            [captureDevice setExposureMode:exposureMode];
        }
    }];
}

//设置聚焦点
- (void)focusWithMode:(AVCaptureFocusMode)focusMode exposureMode:(AVCaptureExposureMode)exposureMode atPoint:(CGPoint)point{
    [self changeDeviceProperty:^(AVCaptureDevice *captureDevice) {
        if ([captureDevice isFocusModeSupported:focusMode]) {
            [captureDevice setFocusMode:AVCaptureFocusModeAutoFocus];
        }
        
        if ([captureDevice isFocusPointOfInterestSupported]) {
            [captureDevice setFocusPointOfInterest:point];
        }
        
        if ([captureDevice isExposureModeSupported:exposureMode]) {
            [captureDevice setExposureMode:AVCaptureExposureModeAutoExpose];
        }
        
        if ([captureDevice isExposurePointOfInterestSupported]) {
            [captureDevice setExposurePointOfInterest:point];
        }
        
    }];
}

//添加点击手势，点按时聚焦
- (void)addGenstureRecognizer{
    UITapGestureRecognizer * tapGesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapScreen:)];
    [self.contentView addGestureRecognizer:tapGesture];
}

//设置闪关灯按钮状态
- (void)setFlashModeButtonStatus{
    
    AVCaptureDevice * captureDevice = [self.captureDeviceInput device];
    AVCaptureFlashMode flashMode = captureDevice.flashMode;
    if ([captureDevice isFlashAvailable]) {
        self.flashAutoButton.hidden = NO;
        self.flashOnButton.hidden  = NO;
        self.flashOffButton.hidden = NO;
        self.flashAutoButton.enabled = YES;
        self.flashOnButton.enabled = YES;
        self.flashOffButton.enabled = YES;
        
        switch (flashMode) {
            case AVCaptureFlashModeAuto:
                self.flashAutoButton.enabled = NO;
                break;
            case AVCaptureFlashModeOn:
                self.flashOnButton.enabled = NO;
                break;
            case AVCaptureFlashModeOff:
                self.flashOffButton.enabled = NO;
                break;
            default:
                break;
        }
    } else {
        self.flashAutoButton.hidden = YES;
        self.flashOnButton.hidden   = YES;
        self.flashOffButton.hidden  = YES;
    }
    
}

//设置聚焦光标位置
- (void)setFocusCursorWithPoint:(CGPoint)point{
    
    self.focusCursor.center = point;
    self.focusCursor.transform = CGAffineTransformMakeScale(1.5, 1.5);
    self.focusCursor.alpha = 1.0;
    [UIView animateWithDuration:1.0 animations:^{
        self.focusCursor.transform = CGAffineTransformIdentity;
    } completion:^(BOOL finished) {
        self.focusCursor.alpha=0;
    }];
}

/**
 *  设备连接成功
 *
 *  @param notification 通知对象
 */
-(void)deviceConnected:(NSNotification *)notification{
    NSLog(@"设备已连接...");
}
/**
 *  设备连接断开
 *
 *  @param notification 通知对象
 */
-(void)deviceDisconnected:(NSNotification *)notification{
    NSLog(@"设备已断开.");
}
/**
 *  捕获区域改变
 *
 *  @param notification 通知对象
 */
-(void)areaChange:(NSNotification *)notification{
    NSLog(@"捕获区域改变...");
}

/**
 *  会话出错
 *
 *  @param notification 通知对象
 */
-(void)sessionRuntimeError:(NSNotification *)notification{
    NSLog(@"会话发生错误.");
}

#pragma mark - 点击方法
- (void)tapScreen:(UITapGestureRecognizer *) tapGesture{

    CGPoint point = [tapGesture locationInView:self.contentView];
    //将UI坐标转化为摄像头坐标
    CGPoint cameraPoint = [self.captureVideoPreviewLayer captureDevicePointOfInterestForPoint:point];
    point.y +=124;
    [self setFocusCursorWithPoint:point];
    [self focusWithMode:AVCaptureFocusModeAutoFocus exposureMode:AVCaptureExposureModeAutoExpose atPoint:cameraPoint];
}

- (void)clickTakeButton:(UIButton *)sender{

    //根据设备输出获得连接
    AVCaptureConnection *captureConnection=[self.captureStillImageOutput connectionWithMediaType:AVMediaTypeVideo];
    //根据连接取得设备输出的数据
    [self.captureStillImageOutput captureStillImageAsynchronouslyFromConnection:captureConnection completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error) {
        if (imageDataSampleBuffer) {
            NSData *imageData=[AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
            UIImage *image=[UIImage imageWithData:imageData];
            UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil);

        }
        
    }];
}

// 打开闪关灯
- (void)clickFlashOnButton:(UIButton *)sender{
    [self setFlashMode:AVCaptureFlashModeOn];
    [self setFlashModeButtonStatus];

}

//关闭闪光灯
- (void)clickFlashOffButton:(UIButton *)sender{
    [self setFlashMode:AVCaptureFlashModeOff];
    [self setFlashModeButtonStatus];

}

//自动闪关灯开起
- (void)clickFlashAutoButton:(UIButton *)sender{
    [self setFlashMode:AVCaptureFlashModeAuto];
    [self setFlashModeButtonStatus];
}

//切换摄像头
- (void)clikcExchangeCamera:(UIButton *)sender{
    AVCaptureDevice * currentDevice = [self.captureDeviceInput device];
    AVCaptureDevicePosition currentPosition = [currentDevice position];
    [self removeNotificationFromCaptureDevice:currentDevice];
    AVCaptureDevice * toChangeDevice;
    AVCaptureDevicePosition  toChangePosition = AVCaptureDevicePositionFront;
    if (currentPosition==AVCaptureDevicePositionUnspecified||currentPosition==AVCaptureDevicePositionFront) {
        toChangePosition = AVCaptureDevicePositionBack;
    }
    toChangeDevice = [self getCameraDeviceWithPosition:toChangePosition];
    [self addNotificationToCaptureDevice:toChangeDevice];
    
    //获得要调整到设备输入对象
    AVCaptureDeviceInput * toChangeDeviceInput = [[AVCaptureDeviceInput alloc]initWithDevice:toChangeDevice error:nil];
    
    //改变会话到配置前一定要先开启配置，配置完成后提交配置改变
    [self.captureSession beginConfiguration];
    //移除原有输入对象
    [self.captureSession removeInput:self.captureDeviceInput];
    //添加新的输入对象
    if ([self.captureSession canAddInput:toChangeDeviceInput]) {
        [self.captureSession addInput:toChangeDeviceInput];
        self.captureDeviceInput=toChangeDeviceInput;
    }
    
    //提交新的输入对象
    [self.captureSession commitConfiguration];
    [self setFlashModeButtonStatus];
}

- (void)clickVideoButton:(UIButton *)sender{

    //根据设备输出获得连接
    AVCaptureConnection *captureConnection=[self.captureMovieFileOutPut connectionWithMediaType:AVMediaTypeVideo];
    //根据连接取得设备输出的数据
    if (![self.captureMovieFileOutPut isRecording]) {
  //      self.enableRotation=NO;
        //如果支持多任务则则开始多任务
        if ([[UIDevice currentDevice] isMultitaskingSupported]) {
            self.backgroundTaskIdentifier=[[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:nil];
        }
        //预览图层和视频方向保持一致
        captureConnection.videoOrientation=[self.captureVideoPreviewLayer connection].videoOrientation;
        NSString *outputFielPath=[NSTemporaryDirectory() stringByAppendingString:@"myMovie.mov"];
        NSLog(@"save path is :%@",outputFielPath);
        NSURL *fileUrl=[NSURL fileURLWithPath:outputFielPath];
        [self.captureMovieFileOutPut startRecordingToOutputFileURL:fileUrl recordingDelegate:self];
    }
    else{
        [self.captureMovieFileOutPut stopRecording];//停止录制
    }
}

#pragma mark - UI相关和布局
- (void)setupUI{
    
    [self.view addSubview:self.contentView];
    self.contentView.frame = CGRectMake(0, 124, ScreenWith, ScreenHeight-60-124);
    
    self.takeButton = [self createCustomButtonWithName:@"拍照"];
    [self.takeButton addTarget:self action:@selector(clickTakeButton:) forControlEvents:UIControlEventTouchUpInside];
    self.takeButton.frame = CGRectMake(ScreenWith/2-30, ScreenHeight-60, 60, 60);
    [self.view addSubview:self.takeButton];
    
    self.videoButton = [self createCustomButtonWithName:@"录像"];
    [self.videoButton addTarget:self action:@selector(clickVideoButton:) forControlEvents:UIControlEventTouchUpInside];
    self.videoButton.frame = CGRectMake(ScreenWith-80, ScreenHeight-60, 60, 60);
    [self.view addSubview:self.videoButton];

    
    CGFloat margin = ((ScreenWith - 4*60)/5);
    self.flashOnButton = [self createCustomButtonWithName:@"打开闪光灯"];
    [self.flashOnButton addTarget:self action:@selector(clickFlashOnButton:) forControlEvents:UIControlEventTouchUpInside];
    self.flashOnButton.frame = CGRectMake(margin, 64, 60, 60);
    [self.view addSubview:self.flashOnButton];
    
    self.flashOffButton = [self createCustomButtonWithName:@"关闭闪光灯"];
    [self.flashOffButton addTarget:self action:@selector(clickFlashOffButton:) forControlEvents:UIControlEventTouchUpInside];
    self.flashOffButton.frame = CGRectMake(60+2*margin, 64, 60, 60);
    [self.view addSubview:self.flashOffButton];
    
    self.flashAutoButton = [self createCustomButtonWithName:@"自动闪光灯"];
    [self.flashAutoButton addTarget:self action:@selector(clickFlashAutoButton:) forControlEvents:UIControlEventTouchUpInside];
    self.flashAutoButton.frame = CGRectMake(2*60+3*margin, 64, 60, 60);
    [self.view addSubview:self.flashAutoButton];
    
    self.exchangeCamera = [self createCustomButtonWithName:@"切换"];
    [self.exchangeCamera addTarget:self action:@selector(clikcExchangeCamera:) forControlEvents:UIControlEventTouchUpInside];
    self.exchangeCamera.frame = CGRectMake(ScreenWith-60-margin, 64, 60, 60);
    [self.view addSubview:self.exchangeCamera];
    
    self.focusCursor = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, 60, 60)];
    self.focusCursor.backgroundColor = [UIColor redColor];
    self.focusCursor.layer.cornerRadius = 30;
    self.focusCursor.layer.masksToBounds = YES;
    [self.view addSubview:self.focusCursor];
    
    
}

- (UIView *)contentView{
    if (!_contentView) {
        _contentView = [[UIView alloc] init];
    }
    return _contentView;
}

- (UIButton *)createCustomButtonWithName:(NSString *)name{
    UIButton * button = [UIButton buttonWithType:UIButtonTypeCustom];
    [button setTitle:name forState:UIControlStateNormal];
    button.backgroundColor = [UIColor redColor];
    button.layer.cornerRadius = 30;
    button.layer.masksToBounds = YES;
    return button;
}

效果图