ios - 在 CALayer 中定位内容

Question

如何在 CALayer 中定位内容，使其缩放以适应宽度(保持纵横比)并定位在层的顶部？

更具体地说，我正在尝试使用 AVCaptureVideoPreviewLayer 实现此定位。如果我将预览层的 videoGravity 设置为 AVLayerVideoGravityResizeAspectFill，那么它将填充宽度但将内容垂直居中在框架中(切断顶部和底部)。

Answer 1

尝试使用 .contentGravity 属性 -

A constant that specifies how the layer's contents are positioned or scaled within its bounds

<CALayer>.contentsGravity = kCAGravityResizeAspect;

可能

CA_EXTERN NSString * const kCAGravityCenter
    __OSX_AVAILABLE_STARTING (__MAC_10_5, __IPHONE_2_0);
CA_EXTERN NSString * const kCAGravityTop
    __OSX_AVAILABLE_STARTING (__MAC_10_5, __IPHONE_2_0);
CA_EXTERN NSString * const kCAGravityBottom
    __OSX_AVAILABLE_STARTING (__MAC_10_5, __IPHONE_2_0);
CA_EXTERN NSString * const kCAGravityLeft
    __OSX_AVAILABLE_STARTING (__MAC_10_5, __IPHONE_2_0);
CA_EXTERN NSString * const kCAGravityRight
    __OSX_AVAILABLE_STARTING (__MAC_10_5, __IPHONE_2_0);
CA_EXTERN NSString * const kCAGravityTopLeft
    __OSX_AVAILABLE_STARTING (__MAC_10_5, __IPHONE_2_0);
CA_EXTERN NSString * const kCAGravityTopRight
    __OSX_AVAILABLE_STARTING (__MAC_10_5, __IPHONE_2_0);
CA_EXTERN NSString * const kCAGravityBottomLeft
    __OSX_AVAILABLE_STARTING (__MAC_10_5, __IPHONE_2_0);
CA_EXTERN NSString * const kCAGravityBottomRight
    __OSX_AVAILABLE_STARTING (__MAC_10_5, __IPHONE_2_0);
CA_EXTERN NSString * const kCAGravityResize
    __OSX_AVAILABLE_STARTING (__MAC_10_5, __IPHONE_2_0);
CA_EXTERN NSString * const kCAGravityResizeAspect
    __OSX_AVAILABLE_STARTING (__MAC_10_5, __IPHONE_2_0);
CA_EXTERN NSString * const kCAGravityResizeAspectFill
    __OSX_AVAILABLE_STARTING (__MAC_10_5, __IPHONE_2_0);