ios - 在 iPhone 上打开手电筒/闪光灯

Question

我知道在 iPhone 4 上打开闪光灯并使其保持打开状态的唯一方法是打开摄像机。我不太确定代码。这是我正在尝试的:

-(IBAction)turnTorchOn {
    AVCaptureSession *captureSession = [[AVCaptureSession alloc] init];
    AVCaptureDevice *videoCaptureDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    NSError *error = nil;
    AVCaptureDeviceInput *videoInput = [AVCaptureDeviceInput deviceInputWithDevice:videoCaptureDevice error:&error];

    if (videoInput) {
        [captureSession addInput:videoInput];

        AVCaptureVideoDataOutput* videoOutput = [[AVCaptureVideoDataOutput alloc] init];
        [videoOutput setSampleBufferDelegate:self queue:dispatch_get_current_queue()];

        [captureSession addOutput:videoOutput];

        [captureSession startRunning];

        videoCaptureDevice.torchMode = AVCaptureTorchModeOn;
    }   
}

有谁知道这是否可行，或者我是否遗漏了什么？ (我还没有要测试的 iPhone 4 - 只是尝试一些新的 API)。

谢谢

Answer 1

这是一个较短的版本，您现在可以使用它来打开或关闭灯:

AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
if ([device hasTorch]) {
    [device lockForConfiguration:nil];
    [device setTorchMode:AVCaptureTorchModeOn];  // use AVCaptureTorchModeOff to turn off
    [device unlockForConfiguration];
}

更新:(2015 年 3 月)

在 iOS 6.0 及更高版本中，您可以使用以下方法控制手电筒的亮度或级别:

- (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];
    }
}

您可能还想监控 setTorchModeOnWithLevel: 的返回值(成功)。如果您尝试将级别设置得太高并且手电筒过热，则可能会失败。在这种情况下，将级别设置为 AVCaptureMaxAvailableTorchLevel 会将级别设置为给定手电筒温度所允许的最高级别。