在啓動時關閉相機對焦

Question

當我用iOS 6在iPad 3上啓動相機時，相機將執行對焦操作。這就是我如何與AVFoundation框架，這樣做：\

// 
// AppDelegate.h 
// 

@interface AppDelegate : UIResponder <UIApplicationDelegate> 

@property (strong, nonatomic) UIWindow *window; 


@property (strong, nonatomic) AVCaptureSession *session; 
@property (strong, nonatomic) AVCaptureVideoPreviewLayer *captureVideoPreviewLayer; 
@property (strong, nonatomic) AVCaptureDevice *device; 
@property (strong, nonatomic) AVCaptureDeviceInput *input; 
@property(nonatomic, strong) AVCaptureStillImageOutput *stillImageOutput; 

@end 

// 
// AppDelegate.m 
// 


@implementation AppDelegate 
@synthesize session; 
@synthesize captureVideoPreviewLayer; 
@synthesize device; 
@synthesize input; 
@synthesize stillImageOutput; 


- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions 
{  
    device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo]; 
    NSError *error = nil; 

    if (([device hasMediaType:AVMediaTypeVideo]) && 
     ([device position] == AVCaptureDevicePositionBack)) { 
     [device lockForConfiguration:&error]; 
     if ([device isFocusModeSupported:AVCaptureFocusModeLocked]) { 
      device.focusMode = AVCaptureFocusModeLocked; 
      NSLog(@"Focus locked"); 
     } 

     [device unlockForConfiguration]; 
    } 

    session = [[AVCaptureSession alloc] init]; 
    session.sessionPreset = AVCaptureSessionPresetPhoto; 

    captureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:session]; 
    [captureVideoPreviewLayer setAffineTransform:CGAffineTransformMakeRotation(-M_PI/2)]; 


    input = [AVCaptureDeviceInput deviceInputWithDevice:device error:&error]; 
    if (!input) { 
     // Handle the error appropriately. 
     NSLog(@"ERROR: trying to open camera: %@", error); 
    } 
    [session addInput:input]; 

    stillImageOutput = [[AVCaptureStillImageOutput alloc] init]; 

    NSDictionary *outputSettings = [[NSDictionary alloc] initWithObjectsAndKeys: AVVideoCodecJPEG, AVVideoCodecKey, nil]; 
    [stillImageOutput setOutputSettings:outputSettings]; 

    [session addOutput:stillImageOutput]; 
    [session startRunning]; 

    return YES; 
} 

我專門就AVDevice在啓動時（device.focusMode = AVCaptureFocusModeLocked;）鎖定對焦，但相機啓動時，它會執行對焦操作。在我的應用程序中，我不希望發生這種情況，以便進行相機校準。

我該如何避免焦點在相機初始化上被觸發？

Answer 1

-(void)disableAutoFocus 
    { 
    AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo]; 
    [device lockForConfiguration:nil]; 
    [device setTorchMode:AVCaptureTorchModeOff]; 
    [device setFlashMode:AVCaptureFlashModeOff]; 

    NSArray *devices = [AVCaptureDevice devices]; 
    NSError *error; 
    for (AVCaptureDevice *device in devices) { 
    if (([device hasMediaType:AVMediaTypeVideo]) && 
     ([device position] == AVCaptureDevicePositionBack)) { 
     [device lockForConfiguration:&error]; 
     if ([device isFocusModeSupported:AVCaptureFocusModeLocked]) { 
      device.focusMode = AVCaptureFocusModeLocked; 
      NSLog(@"Focus locked"); 
     } 

     [device unlockForConfiguration]; 
    } 
} 

}