imageView.image = UIImage(ciImage: ) 不会更新第二次

Question

案例：我在视图中有一个 UISwitch 按钮。当开关关闭时，imageView 将显示从字符串生成的 QRCode 图像。打开时，它将显示从字符串生成的条形码图像。我从 https://www.hackingwithswift.com/ 复制了 QRCode 和条形码生成函数，它们工作正常。

问题是 imageView 仅在第一次显示生成的图像。在 QRCode 和条形码之间切换时，imageView 将不再更新。我 100% 确定 UISwitch 正在工作，函数被调用并返回生成的图像。我用断点和打印测试了很多次，函数没有返回 nil 或空图像。

这里是二维码生成码

func generateQRCode(from string: String) -> UIImage? {
    let data = string.data(using: String.Encoding.ascii)

    if let filter = CIFilter(name: "CIQRCodeGenerator") {
        filter.setValue(data, forKey: "inputMessage")
        let transform = CGAffineTransform(scaleX: 3, y: 3)

        if let output = filter.outputImage?.transformed(by: transform) {
            return UIImage(ciImage: output) //<== it always returns this
        }
    }
    return nil
}

这里是条形码生成代码

func generateBarcode(from string: String) -> UIImage? {
    let data = string.data(using: String.Encoding.ascii)

    if let filter = CIFilter(name: "CICode128BarcodeGenerator") {
        filter.setValue(data, forKey: "inputMessage")
        let transform = CGAffineTransform(scaleX: 3, y: 3)

        if let output = filter.outputImage?.transformed(by: transform) {
            return UIImage(ciImage: output) //<== it always returns this
        }
    }
    return nil
}

我是这样切换QRCode和条码的逻辑正确

func toggleBarcode(isBarcode : Bool) {
    if isBarcode {
        qrImageView.image = generateBarcode(from: "Hacking with Swift")
    } else {
        qrImageView.image = generateQRCode(from: "Hacking with Swift")
    }
}

使用类似

的东西进行测试时

qrImageView.image = UIImage(named: "myimage")

每次都有效。

imageView 不会只更新 UIImage(ciImage: )

我什至测试了几个不同版本的 QR 和条形码生成代码，它们都不会第二次更新 imageView。

我试过了

qrImageView.setNeedsDisplay()

但运气不好。

Answer 1

快速搜索...似乎是“错误”或更改...

将您的生成器代码更改为此似乎可以解决问题：

func generateQRCode(from string: String) -> UIImage? {
    let data = string.data(using: String.Encoding.ascii)

    let context = CIContext()

    if let filter = CIFilter(name: "CIQRCodeGenerator") {
        filter.setValue(data, forKey: "inputMessage")
        let transform = CGAffineTransform(scaleX: 3, y: 3)
        
        if let output = filter.outputImage?.transformed(by: transform) {
            if let retImg = context.createCGImage(output, from: output.extent) {
                return UIImage(cgImage: retImg)
            }
        }
    }
    return nil
}

func generateBarcode(from string: String) -> UIImage? {
    let data = string.data(using: String.Encoding.ascii)

    let context = CIContext()

    if let filter = CIFilter(name: "CICode128BarcodeGenerator") {
        filter.setValue(data, forKey: "inputMessage")
        let transform = CGAffineTransform(scaleX: 3, y: 3)
        
        if let output = filter.outputImage?.transformed(by: transform) {
            if let retImg = context.createCGImage(output, from: output.extent) {
                return UIImage(cgImage: retImg)
            }
        }
    }
    return nil
}

imageView.image = UIImage(ciImage: ) 不会更新第二次

imageView.image = UIImage(ciImage: ) won't update a second time

uiimage

ios

ciimage

swift