// Lock the focus as the first step for a still image capture.
private void LockFocus()
{
try
{
var availableAutoFocusModes = (int[])characteristics.Get(CameraCharacteristics.ControlAfAvailableModes);
// Set autofocus if supported
if (availableAutoFocusModes.Any(afMode => afMode != (int)ControlAFMode.Off))
{
previewRequestBuilder.Set(CaptureRequest.ControlAfTrigger, (int)ControlAFTrigger.Start);
state = MediaCaptorState.WaitingLock;
// Tell cameraCaptureCallback to wait for the lock.
captureSession.Capture(previewRequestBuilder.Build(), cameraCaptureCallback,
backgroundHandler);
}
else
{
// If autofocus is not enabled, just capture the image
CaptureStillPicture();
}
}
catch (CameraAccessException e)
{
e.PrintStackTrace();
}
}
private void ProcessImageCapture(CaptureResult result)
{
switch (state)
{
case MediaCaptorState.WaitingLock:
{
var afState = (int?)result.Get(CaptureResult.ControlAfState);
if (afState == null)
{
CaptureStillPicture();
}
else if ((((int)ControlAFState.FocusedLocked) == afState.Value) ||
(((int)ControlAFState.NotFocusedLocked) == afState.Value))
{
// ControlAeState can be null on some devices
var aeState = (int?)result.Get(CaptureResult.ControlAeState);
if (aeState == null || aeState.Value == ((int)ControlAEState.Converged))
{
state = MediaCaptorState.PictureTaken;
CaptureStillPicture();
}
else
{
RunPrecaptureSequence();
}
}
break;
}
case MediaCaptorState.WaitingPrecapture:
{
// ControlAeState can be null on some devices
var aeState = (int?)result.Get(CaptureResult.ControlAeState);
if (aeState == null ||
aeState.Value == ((int)ControlAEState.Precapture) ||
aeState.Value == ((int)ControlAEState.FlashRequired))
{
state = MediaCaptorState.WaitingNonPrecapture;
}
break;
}
case MediaCaptorState.WaitingNonPrecapture:
{
// ControlAeState can be null on some devices
var aeState = (int?)result.Get(CaptureResult.ControlAeState);
if (aeState == null || aeState.Value != ((int)ControlAEState.Precapture))
{
state = MediaCaptorState.PictureTaken;
CaptureStillPicture();
}
break;
}
}
}
// Run the precapture sequence for capturing a still image. This method should be called when
// we get a response in captureCallback from LockFocus().
public void RunPrecaptureSequence()
{
try
{
// This is how to tell the camera to trigger.
previewRequestBuilder.Set(CaptureRequest.ControlAePrecaptureTrigger, (int)ControlAEPrecaptureTrigger.Start);
// Tell captureCallback to wait for the precapture sequence to be set.
state = MediaCaptorState.WaitingPrecapture;
captureSession.Capture(previewRequestBuilder.Build(), cameraCaptureCallback, backgroundHandler);
}
catch (CameraAccessException e)
{
e.PrintStackTrace();
}
}
void UnlockFocus()
{
try
{
// Reset the auto-focus trigger
previewRequestBuilder.Set(CaptureRequest.ControlAfTrigger, (int)ControlAFTrigger.Cancel);
SetAutoFlash(previewRequestBuilder);
captureSession.Capture(previewRequestBuilder.Build(), cameraCaptureCallback,
backgroundHandler);
// After this, the camera will go back to the normal state of preview.
state = MediaCaptorState.Preview;
captureSession.SetRepeatingRequest(previewRequest, cameraCaptureCallback,
backgroundHandler);
}
catch (CameraAccessException e)
{
e.PrintStackTrace();
}
}
