PLVMediaPlayerAspectRatio

按比例缩放，直到有一边到达容器边界，可能会有黑边

按比例缩放，直到填满容器，可能会有视频内容裁剪

以16:9的比例适应缩放，可能会有黑边

以4:3的比例适应缩放，可能会有黑边

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Returns an array containing the constants of this enum type, in the order they're declared.