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/**
 * 从相机支持的分辨率中计算出最适合的预览界面尺寸
 *
 * @param parameters
 * @param screenResolution
 * @return
 */
private Point findBestPreviewSizeValue(Camera.Parameters parameters, Point screenResolution) {
    List<Camera.Size> rawSupportedSizes = parameters.getSupportedPreviewSizes();
    if (rawSupportedSizes == null) {
        Log.w(TAG, "Device returned no supported preview sizes; using default");
        Camera.Size defaultSize = parameters.getPreviewSize();
        return new Point(defaultSize.width, defaultSize.height);
    }

    // Sort by size, descending
    List<Camera.Size> supportedPreviewSizes = new ArrayList<Camera.Size>(rawSupportedSizes);
    Collections.sort(supportedPreviewSizes, new Comparator<Camera.Size>() {
        @Override
        public int compare(Camera.Size a, Camera.Size b) {
            int aPixels = a.height * a.width;
            int bPixels = b.height * b.width;
            if (bPixels < aPixels) {
                return -1;
            }
            if (bPixels > aPixels) {
                return 1;
            }
            return 0;
        }
    });

// if (Log.isLoggable(TAG, Log.INFO)) {
// StringBuilder previewSizesString = new StringBuilder();
// for (Camera.Size supportedPreviewSize : supportedPreviewSizes) {
// previewSizesString.append(supportedPreviewSize.width).append(‘x’).append(supportedPreviewSize.height).append(’ ‘);
// }
// Log.i(TAG, “Supported preview sizes: ” + previewSizesString);
// }

    double screenAspectRatio = (double) screenResolution.x / (double) screenResolution.y;

    // Remove sizes that are unsuitable
    Iterator<Camera.Size> it = supportedPreviewSizes.iterator();
    while (it.hasNext()) {
        Camera.Size supportedPreviewSize = it.next();
        int realWidth = supportedPreviewSize.width;
        int realHeight = supportedPreviewSize.height;
        if (realWidth * realHeight < MIN_PREVIEW_PIXELS) {
            it.remove();
            continue;
        }

        boolean isCandidatePortrait = realWidth < realHeight;
        int maybeFlippedWidth = isCandidatePortrait ? realHeight : realWidth;
        int maybeFlippedHeight = isCandidatePortrait ? realWidth : realHeight;

        double aspectRatio = (double) maybeFlippedWidth / (double) maybeFlippedHeight;
        double distortion = Math.abs(aspectRatio - screenAspectRatio);
        if (distortion > MAX_ASPECT_DISTORTION) {
            it.remove();
            continue;
        }

        if (maybeFlippedWidth == screenResolution.x && maybeFlippedHeight == screenResolution.y) {
            Point exactPoint = new Point(realWidth, realHeight);
            Log.i(TAG, "Found preview size exactly matching screen size: " + exactPoint);
            return exactPoint;
        }
    }

    // If no exact match, use largest preview size. This was not a great
    // idea on older devices because
    // of the additional computation needed. We're likely to get here on
    // newer Android 4+ devices, where
    // the CPU is much more powerful.
    if (!supportedPreviewSizes.isEmpty()) {
        Camera.Size largestPreview = supportedPreviewSizes.get(0);
        Point largestSize = new Point(largestPreview.width, largestPreview.height);
        Log.i(TAG, "Using largest suitable preview size: " + largestSize);
        return largestSize;
    }

    // If there is nothing at all suitable, return current preview size
    Camera.Size defaultPreview = parameters.getPreviewSize();
    Point defaultSize = new Point(defaultPreview.width, defaultPreview.height);
    Log.i(TAG, "No suitable preview sizes, using default: " + defaultSize);

    return defaultSize;
}