android - 使用 Google Vision 条码阅读器访问 AutoFocus/Flash

Question

我在这里玩条形码扫描器的原始示例:

https://github.com/googlesamples/android-vision/blob/master/visionSamples/barcode-reader/app/src/main/java/com/google/android/gms/samples/vision/barcodereader/BarcodeCaptureActivity.java

他们可以像这样在相机工厂内启动自动对焦/闪光灯:

    // Creates and starts the camera.  Note that this uses a higher resolution in comparison
    // to other detection examples to enable the barcode detector to detect small barcodes
    // at long distances.
    CameraSource.Builder builder = new CameraSource.Builder(getApplicationContext(), barcodeDetector)
            .setFacing(CameraSource.CAMERA_FACING_BACK)
            .setRequestedPreviewSize(1600, 1024)
            .setRequestedFps(15.0f);

    // make sure that auto focus is an available option
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
        builder = builder.setFocusMode(
                autoFocus ? Camera.Parameters.FOCUS_MODE_CONTINUOUS_PICTURE : null);
    }

    mCameraSource = builder
            .setFlashMode(useFlash ? Camera.Parameters.FLASH_MODE_TORCH : null)
            .build();

但是，当前版本中 cameraSource 构建器上的此方法已不存在，因此无法访问此设置。此外，我需要在使用过程中更改 FlashMode，所以这也不是这样做的方法。我发现了这个丑陋的访问相机的解决方案:

public static Camera getCamera(@NonNull CameraSource cameraSource) {
    Field[] declaredFields = CameraSource.class.getDeclaredFields();

    for (Field field : declaredFields) {
        if (field.getType() == Camera.class) {
            field.setAccessible(true);
            try {
                Camera camera = (Camera) field.get(cameraSource);
                if (camera != null) {
                    return camera;
                }

                return null;
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }

            break;
        }
    }

    return null;
}

虽然有效，但无济于事:调用 getParameters().setFocusMode() 时出现此异常:

Attempt to invoke virtual method 'android.hardware.Camera$Parameters android.hardware.Camera.getParameters()' on a null object reference

显然我正在做的不是正确的方法，但似乎没有关于它的文档。

感谢提示。

Answer 1

只需如下优化您的代码，您必须在构建 Camera Source 类后调用此方法。

private Camera camera = null;
boolean flashmode=false;
private void flashOnButton() {
    camera=getCamera(mCameraSource);
    if (camera != null) {
        try {
            Camera.Parameters param = camera.getParameters();
         param.setFlashMode(!flashmode?Camera.Parameters.FLASH_MODE_TORCH :Camera.Parameters.FLASH_MODE_OFF);
            camera.setParameters(param);
            flashmode = !flashmode;
            if(flashmode){
                showToast("Flash Switched ON");
            }
            else {
                showToast("Flash Switched Off");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

    }
}
private static Camera getCamera(@NonNull CameraSource cameraSource) {
    Field[] declaredFields = CameraSource.class.getDeclaredFields();

    for (Field field : declaredFields) {
        if (field.getType() == Camera.class) {
            field.setAccessible(true);
            try {
                Camera camera = (Camera) field.get(cameraSource);
                if (camera != null) {
                    return camera;
                }
                return null;
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
            break;
        }
    }
    return null;
}

这将帮助您使用 camerasource 对象在 Google Vision Api 中启用闪光灯。