swiftUI transitions: Scale from some frame - like

Question

How do I get the effect in a translation, that iOS home screen does when opening an App: It scales the App to fullscreen, starting from the App-icon on the home screen?

In my code, I have the icon-frame (CGRect) with position, width and height and I have the final frame. Is there a way to (probably combine some) transitions to get a scaling from the icon-frame to the final frame?

I get somewhat similar with:

view.transition(AnyTransition.scale(scale: 0, anchor: UnitPoint.trailing))

Which scales from zero to the original size, starting from trailing center position. It's only close as:

• it scales from zero instead of the size of the original icon
• it starts from a fixed point (trailing, center) but I'd like to let it start from where the icon is.

Just to be sure: It must be a transition as the view is newly created and dropped. I tried with keeping the view and just change its opacity to show/hide it. With many other problems like not getting the reverse animation, when the view disappears.

Answer 1

The above sample code should give you an idea on scaling an image

struct ImageCustomScaling: View {
    // image to be scaled
    var scaleImage: Image

    // scale ratio
    var scaleTo: Double

    @State private var start = false

    var body: some View {

        VStack {

            scaleImage
                .font(.title)
                .scaleEffect(self.start ? CGFloat(scaleTo) : 1)
                .opacity(self.start ? 1 : 0)
                .animation(Animation.interpolatingSpring(stiffness: 25, damping: 5, initialVelocity: 10).delay(0.9))

        }
        .foregroundColor(.blue)
        .onAppear {
            self.start = true
        }
    }

}

Above can be called by something like below

ImageCustomScaling(scaleImage: Image(systemName: "cloud.fill"), scaleTo: 5 )

Added animation modifier to give visual cue. You can change it to meet your needs.

Answer 2

Here is a demo of idea how such effect could be done with combined transitions... (positions and sizes are hardcoded for demo simplicity - they can be read with geometry reader, alignment guides or anchor preferences, and actually do not affect the transition usage idea, also animation can be configured)

Demo:

struct TestRisingView: View {

    let screen = UIScreen.main.bounds

    @State var showingView = false
    @State var btFrame: CGRect = .zero

    var body: some View {
        GeometryReader { g in
            ZStack {
                Rectangle().fill(Color.clear)

                self.activatingButton(frame: CGRect(x: 80, y: 30, width: 60, height: 40))
                self.activatingButton(frame: CGRect(x: self.screen.maxX - 80, y: 30, width: 60, height: 40))
                self.activatingButton(frame: CGRect(x: self.screen.maxX - 80, y: self.screen.maxY - 60, width: 60, height: 40))
                self.activatingButton(frame: CGRect(x: 80, y: self.screen.maxY - 60, width: 60, height: 40))

                if self.showingView {
                    self.topView
                        .zIndex(1)
                        .transition(
                            AnyTransition.scale(scale: 0.12).combined(with:
                            AnyTransition.offset(x: self.btFrame.origin.x - g.size.width/2.0,
                                                 y: self.btFrame.origin.y - g.size.height/2.0))
                        )
                }
            }
        }
    }

    func activatingButton(frame: CGRect) -> some View {
        Button(action: {
            withAnimation {
                self.btFrame = frame
                self.showingView.toggle()
            }
        }) {
            Text("Tap")
                .padding()
                .background(Color.yellow)
        }
        .position(frame.origin)
    }

    var topView: some View {
        Rectangle()
            .fill(Color.green)
            .frame(width: 300, height: 400)
    }
}

struct TestRisingView_Previews: PreviewProvider {
    static var previews: some View {
        TestRisingView()
    }
}