ios – AVFoundation：isExposureModeSupported为AVCaptureExpos

我在iPhone 5上测试,AVCaptureDevice告诉我BackCamera不支持AVCaptureExposureModeAutoExpose.

然后我如何实施水龙头来调整曝光？

这是我的代码：

- (void)didTapCameraPreview:(UITapGestureRecognizer *)recognizer {

CGPoint point = [recognizer locationInView:self.view];
CGRect screenRect = [self.view bounds];
CGFloat screenWidth = screenRect.size.width;
CGFloat screenHeight = screenRect.size.height;
double focus_x = point.x/screenWidth;
double focus_y = point.y/screenHeight;

CGPoint touchPoint = CGPointMake(focus_x,focus_y);

AVCaptureDevice *device = (self.captureSession.inputs[0] == self.backCamera) ? self.backCamera.device : self.frontCamera.device;

if (device.isFocusPointOfInterestSupported) {
    NSError *error;
    if ([device lockForConfiguration:&error]) {
        [device setFocusPointOfInterest:touchPoint];
        [device setExposurePointOfInterest:touchPoint];

        [device setFocusMode:AVCaptureFocusModeAutoFocus];
        if ([device isExposureModeSupported:AVCaptureExposureModeAutoExpose]){
            [device setExposureMode:AVCaptureExposureModeAutoExpose];
        }
        [device unlockForConfiguration];
    }
}

}