CODEWITHSUNDEEP
iosiphoneswiftasynchronousuiview
GonnaGetGet
GonnaGetGet

Reputation: 254

How to continuously update drawing in UIView

I am continuously reading data (CGFloat array) from a source, and I want to draw a line on a UIView from the data points on that source.

I understand that I need to use UIBezierPath to create the line. I am able to do so initially, but I do not know how to keep on updating the drawing on the UIView [like a series of path.move(..)].

Does anyone know how to implement this?

TIA

Upvotes: 0

Views: 1943

Answers (1)

norders
norders

Reputation: 1252

Sub-class UIView and override the draw rect method:

import UIKit

class MyLineView: UIView {
    // Edit:add the data to draw
    public var lineData : Array<Float>?

    override func draw(_ rect: CGRect) {
        // Read the values and draw the lines
        // using your bezier functions

        // Edit: just to test - you can see the new data
        if let data = lineData {
            print("Redrawing \(data.count) elements")
        }
    }
}

In your view controller create a property of type Timer and start it going at an appropriate point with your desired frame rate:

import UIKit

class ViewController: UIViewController {

    var animationTimer : Timer?
    var myLineView : MyLineView?
    **// Edit: add an array of data**
    var myData : Array<Float>?

    override func viewDidLoad() {
        super.viewDidLoad()

        self.myLineView = MyLineView(frame: self.view.bounds)
        self.view.addSubview(myLineView!)
        // Edit: init data
        self.myData = Array()
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)

        // Update the view at roughly 10Hz
        animationTimer = Timer.scheduledTimer(withTimeInterval: 0.1, repeats: true, block: { (timer) in
            //Edit: example update of the data before redrawing
            self.myData?.append(Float(1))
            self.myLineView!.lineData = self.myData!

            self.myLineView!.setNeedsDisplay()
        })
    }

    override func viewDidDisappear(_ animated: Bool) {
        super.viewDidDisappear(animated)

        // Stop updating
        animationTimer!.invalidate()
        animationTimer = nil
    }
}

This will call drawRect on your subclass at an approximate rate of 10Hz.

Upvotes: 1

Related Questions