android自定义相机黑屏问题

对于一些手机，像HTC，当自定义Camera时，调用Camera.Parameters的parameters.setPreviewSize(width,height)方法时，如果width和height为奇数情况下，则会出现黑屏现象，解决办法可参考SDK提供的ApiDemos中关于Camera的例子：

List<Size> sizes =parameters.getSupportedPreviewSizes();

Size optimalSize = getOptimalPreviewSize(sizes, w,h);
parameters.setPreviewSize(optimalSize.width, optimalSize.height);

同时，在HTC手机中，设置parameters.setPictureSize(width,height)属性，也会导致黑屏，而在三星手机上则没有问题。还有如果设置setPreviewSize属性的宽高错误的话，拍出的照片也会存在失真等Bug，所以遇到适配问题时，最好的办法就是不设置PreviewSize和PictureSize属性。

getOptimalPreviewSize方法

private Size getOptimalPreviewSize(List<Size> sizes, int w, int h) {
  final double ASPECT_TOLERANCE = 0.05;
  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;
 }