• 最近在做畢設(shè)奏路，需要固定相機(jī)焦距，但是固定死了也不好斜脂，想著怎么自己去調(diào)整相機(jī)的焦距触机，翻了半天只發(fā)現(xiàn)AVCaptureDevice有設(shè)置焦距模式的玷或，可是沒看見調(diào)整焦距的呀庐椒？看起來有點(diǎn)關(guān)聯(lián)的adjustingFocus竟然是個(gè)BOOL型
  ??

  
  
  AVCaptureDevice Focus章節(jié)

• 正準(zhǔn)備放棄在AVCaptureDevice類中找的時(shí)候在focusMode的枚舉定義里發(fā)現(xiàn)了這樣一個(gè)關(guān)鍵詞

focusMode枚舉

• 英文太菜并不認(rèn)識這個(gè)詞，但是它說被鎖定在len`s當(dāng)前的位置犁钟，那肯定與這個(gè)len`s有關(guān)泼橘，查一查詞典是“鏡頭”的意思??炬灭。再翻一遍文檔發(fā)現(xiàn)了重點(diǎn)：

  
  
  設(shè)置焦距的耶

• 測試一把重归，搞定收工，代碼如下：

#import "ViewController.h"
#import <AVFoundation/AVFoundation.h>
#import <MobileCoreServices/MobileCoreServices.h>

#define XBScreenWidth   [UIScreen mainScreen].bounds.size.width
#define XBScreenHeight   [UIScreen mainScreen].bounds.size.height

@interface ViewController () <AVCaptureVideoDataOutputSampleBufferDelegate>

@property (strong, nonatomic) AVCaptureSession *avSession;
@property (strong, nonatomic) AVCaptureDevice *backCameraDevice;

@end

@implementation ViewController

- (void)viewDidLoad {
#if TARGET_OS_SIMULATOR
    NSAssert(0, @"請使用真機(jī)測試");
#endif
    [super viewDidLoad];
    [self setupSession];
}

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    if (!_avSession.isRunning) {
        [_avSession startRunning];
    }
}

- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
    if (!_avSession.isRunning) {
        [_avSession stopRunning];
    }
}

- (AVCaptureDevice *)backCamera
{
    NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
    for (AVCaptureDevice *device in devices) {
        if (device.position == AVCaptureDevicePositionBack) {
            return device;
        }
    }
    return nil;
}

- (void)setupSession
{
    //創(chuàng)建session會話
    _avSession = [[AVCaptureSession alloc] init];
    [_avSession beginConfiguration];
    _avSession.sessionPreset = AVCaptureSessionPreset640x480;
    //通過capture對象創(chuàng)建輸入設(shè)備對象
    NSError *error = nil;
    _backCameraDevice = [self backCamera];
    [_backCameraDevice lockForConfiguration:&error];
    _backCameraDevice.focusMode = AVCaptureFocusModeLocked;
    [_backCameraDevice unlockForConfiguration];
    AVCaptureDeviceInput *inputDevice = [AVCaptureDeviceInput deviceInputWithDevice:_backCameraDevice error:&error];
    //將輸入設(shè)備添加到會話
    if ([_avSession canAddInput:inputDevice]) {
        [_avSession addInput:inputDevice];
    }else{
        NSLog(@"不能添加視頻輸入設(shè)備");
        return;
    }
    //添加一個(gè)輸出設(shè)備
    AVCaptureVideoDataOutput *videoOutput = [[AVCaptureVideoDataOutput alloc] init];
    videoOutput.videoSettings = @{(__bridge NSString *)kCVPixelBufferPixelFormatTypeKey : [NSNumber numberWithUnsignedInt:kCVPixelFormatType_32BGRA]};
    
    videoOutput.alwaysDiscardsLateVideoFrames = YES;
    
    if ([_avSession canAddOutput:videoOutput]) {
        [_avSession addOutput:videoOutput];
    }else{
        NSLog(@"不能添加視頻輸出設(shè)備");
        return;
    }
    
    AVCaptureVideoPreviewLayer *previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:_avSession];
    //只有設(shè)置GravityResizeAspectFill或GravityResize椎木，然后設(shè)置frame才有效，圖像不會按照frame的大小顯示
    previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
    previewLayer.frame = CGRectMake(0, 20, 320, 240);
    [self.view.layer addSublayer:previewLayer];

    [_avSession commitConfiguration];
}

#pragma mark -
#pragma mark IBAction

- (IBAction)foucsChange:(UISlider *)sender {
    
    NSError *error = nil;
    [_backCameraDevice lockForConfiguration:&error];
    [_backCameraDevice setFocusModeLockedWithLensPosition:sender.value completionHandler:nil];
    [_backCameraDevice unlockForConfiguration];
    
}

@end