ios - 如何保存应用于 UIView 的 CATransform3D

Question

我有一个应用了 CATransform3D 的 View (Uiview)，当我再次打开应用程序时，我想创建一个相同的 View

所以我这样做:保存转换以便稍后在打开的应用程序中使用它

   let radian_vertical =  element.layer.value(forKeyPath: "transform.rotation.y") as? NSNumber ?? 0
    let degree_vertical = (radian_vertical.floatValue) * 180 / (Float)(Double.pi)

    let radian_horizontal =  element.layer.value(forKeyPath: "transform.rotation.x") as? NSNumber ?? 0

   let degree_hori = (radian_horizontal.floatValue) * 180 / (Float)(Double.pi)

但是后来应用的时候不对

//saved_degree_vertical and saved_degree_hori. is saved from degree_vertical and degree_hori

 let radians_verti =  saved_degree_vertical * (CGFloat)(Double.pi)  / 180
 let radians_hori =  saved_degree_hori * (CGFloat)(Double.pi)  / 180
 let rotateVertical = CATransform3DRotate(newViewContent.layer.transform, CGFloat(radians_verti), 0, 1, 0)

 let rotateHorizontal = CATransform3DRotate(newViewContent.layer.transform, CGFloat(radians_hori), 1, 0, 0)

 newViewContent.layer.transform=  rotateHorizontal
 newViewContent.layer.transform =  rotateVertical
//save degree

Answer 1

您应该保存整个矩阵，而不仅仅是一些旋转。 CATransform3D 由 16 个值组成，因为它是 4x4 矩阵。这些属性被命名为 m12、m13、...、m43、m44。它还具有一个采用所有这些属性的构造函数。

您甚至可以将所有 16 个值序列化为一个字符串，然后反序列化它以使其更容易。看到如下内容:

/// A method to save the current view matrix
func saveCurrentMatrix() {
    UserDefaults.standard.set(serializeViewMatrix(view: viewContent), forKey: "my_saved_matrix")
}

/// A method to apply the saved matrix to current view
func loadCurrentMatrix() {
    do {
        try applyViewMatrixFromSerializedString(view: viewContent, string: UserDefaults.standard.string(forKey: "my_saved_matrix"))
    } catch {
        if let description = (error as NSError).userInfo["dev_info"] as? String {
            print("Error occured applying saved matrix: \(description)")
        }
    }
}

/// Serializes a view.layer.transform matrix into string
///
/// - Parameter view: A view to save matrix from
/// - Returns: A string representation of the matrix. In format 1;0;0;0;0;1;0;0;0 ...
func serializeViewMatrix(view: UIView) -> String {
    let matrix: CATransform3D = view.layer.transform
    let values: [CGFloat] = [
        matrix.m11, matrix.m12, matrix.m13, matrix.m14,
        matrix.m21, matrix.m22, matrix.m23, matrix.m24,
        matrix.m31, matrix.m32, matrix.m33, matrix.m34,
        matrix.m41, matrix.m42, matrix.m43, matrix.m44
    ]
    return values.map { String(Double($0)) }.joined(separator: ";")
}

/// Creates a matrix from string produced by serializeViewMatrix and applies it to given view
///
/// - Parameters:
///   - view: A view to apply matrix to
///   - string: A string representing the matrix
/// - Throws: Will throw on incorrect data
func applyViewMatrixFromSerializedString(view: UIView, string: String?) throws {
    guard let string = string else { return } // Simply return if there is no string

    // Genereate 16 string componets separated by ";"
    let components = string.components(separatedBy: ";")
    guard components.count == 16 else { throw NSError(domain: "Matrix serialization", code: 400, userInfo: [ "dev_info": "Incorrect number of components for matrix. Expected 16, got \(components.count)" ]) }

    // Parse string compoenets to CGFloat values
    let values: [CGFloat] = components.compactMap {
        guard let doubleValueRepresentation = Double($0) else { return nil }
        return CGFloat(doubleValueRepresentation)
    }
    guard values.count == 16 else { throw NSError(domain: "Matrix serialization", code: 500, userInfo: [ "dev_info": "Unable to parse all values. \(components.count) out of 16 values were correctly paresed" ]) }

    // Generate and apply transform
    view.layer.transform = CATransform3D(m11: values[0], m12: values[1], m13: values[2], m14: values[3],
                                         m21: values[4], m22: values[5], m23: values[6], m24: values[7],
                                         m31: values[8], m32: values[9], m33: values[10], m34: values[11],
                                         m41: values[12], m42: values[13], m43: values[14], m44: values[15])
}