How to get optimal preview size of custom camera in Android

OptimalCameraPreview.java

Camera.Parameters parameters = mCamera.getParameters();
List<Size> mSupportedPreviewSizes = parameters.getSupportedPreviewSizes();
Size mPreviewSize = getOptimalPreviewSize(mSupportedPreviewSizes, width, height);

   private Size getOptimalPreviewSize(List<Size> sizes, int w, int h) {
        final double ASPECT_TOLERANCE = 0.2;
        double targetRatio = (double) w / h;
        if (sizes == null) return null;
        Size optimalSize = null;
        double minDiff = Double.MAX_VALUE;
        int targetHeight = h;
        // Try to find an size match aspect ratio and size
        for (Size size : sizes) {
            double ratio = (double) size.width / size.height;
            if (Math.abs(ratio - targetRatio) > ASPECT_TOLERANCE) continue;
            if (Math.abs(size.height - targetHeight) < minDiff) {
                optimalSize = size;
                minDiff = Math.abs(size.height - targetHeight);
            }
        }
        // Cannot find the one match the aspect ratio, ignore the requirement
        if (optimalSize == null) {
            minDiff = Double.MAX_VALUE;
            for (Size size : sizes) {
                if (Math.abs(size.height - targetHeight) < minDiff) {
                    optimalSize = size;
                    minDiff = Math.abs(size.height - targetHeight);
                }
            }
        }
        return optimalSize;
    }