ios - setTorchModeOnWithLevel 不工作

Question

我正在使用这种方法打开手电筒:

- (void)checkTorch {
    for (AVCaptureDevice *device in [AVCaptureDevice devices]) {

        if ([device position] != AVCaptureDevicePositionBack) {
            NSLog(@"This is the front camera");
            continue; // go to next device
        }

        NSLog(@"This is the back camera");

        if([device hasTorch] == NO){
            NSLog(@"this camera has no torch...");
            continue; // go to next device
        }

        NSLog(@"The camera has a torch");

        if([device isTorchAvailable] == NO){
            NSLog(@"The torch is not available...");
            continue; // go to next device
        }

        NSLog(@"The torch is available");

        NSError *outError;
        NSError *lockError;

        [device lockForConfiguration:&lockError];
        BOOL success = [device setTorchModeOnWithLevel:0.2 error:&outError];
        [device unlockForConfiguration];

        if (lockError)
            NSLog(@"Error locking: %@", lockError.localizedDescription);

        NSLog(@"Torch Level: %0.0f", device.torchLevel);

        if(!success){
            NSLog(@"Could not activate torch: %@", [outError localizedDescription]);
            continue; // go to next device
        }

        NSLog(@"The torch is now active!");
    }
}

这给了我这个输出(这是正确的):

2014-06-10 08:52:30.677 [291:17894] This is the back camera

2014-06-10 08:52:30.679 [291:17894] The camera has a torch

2014-06-10 08:52:30.679 [291:17894] The torch is available

2014-06-10 08:52:30.682 [291:17894] Torch Level: 0

2014-06-10 08:52:30.683 [291:17894] The torch is now active!

2014-06-10 08:52:30.683 [291:17894] This is the front camera

2014-06-10 08:52:30.684 [291:17894] This is the front camera

但是 torch 从未亮起。

-- 我正在运行测试版代码，但最新的 API 差异显示此方法或相关方法没有变化，所以我不确定为什么它不起作用。我在没有帮助的情况下在苹果开发论坛上问过。

Answer 1

我目前成功地使用以下代码控制 iPhone 5、6 和 6 Plus 上的手电筒:

- (void)setTorchToLevel:(float)torchLevel
{
    AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    if ([device hasTorch]) {
        [device lockForConfiguration:nil];
        if (torchLevel <= 0.0) {
            [device setTorchMode:AVCaptureTorchModeOff];
        }
        else {
            if (torchLevel >= 1.0)
                torchLevel = AVCaptureMaxAvailableTorchLevel;
            BOOL success = [device setTorchModeOnWithLevel:torchLevel   error:nil];
        }
        [device unlockForConfiguration];
    }
}