启用“颜色混合图层”时，是否可以将非英文字符的UILabel设为绿色？ [英] Is it possible to make UILabel with non-English characters green when Color Blended Layer is enabled?

问题描述

我有一个带有自定义单元格的表格视图，我尝试通过在模拟器中选中颜色混合图层时使单元格内的所有子视图都为绿色来优化它。

I have a table view with custom cells and I try to optimize it by making all subviews inside the cells in green color when Color Blended Layer is checked in the simulator.

当单元格中 UILabel 的背景设置为白色时：

When the background of an UILabel in the cell is set to white:

let title = UILabel()
contentView.addSubview(title)
title.background = UIColor.whiteColor()
title.text = "Hi, how are you?"

这个UILabel子视图在模拟器中会变成绿色，这很好。但是，如果我将文本更改为中文：

This UILabel subview will become green color in the simulator, which is good. However, if I change the text to some Chinese:

title.text = "你好"

UILabel子视图将变为红色。这个 SO帖子提供了一些关于情况。实际上有解决方案吗？

The UILabel subview will become red. This SO post provides some explanation about the situation. Is there actually a solution for this?

推荐答案

使用 CATextLayer 代替 UILabel 。并且不要忘记将 opaque 属性设置为 true 。

Use CATextLayer instead of UILabel. And don't forget to set its opaque property to true.

override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath)

        // You should definitely put layer handling logic into 
        // UITableViewCell subclass. I'm omitting it for clarity
    let layer = cell.contentView.layer

    let textLayer = CATextLayer()
    textLayer.string = "你好"
    textLayer.bounds = CGRect(x: 0, y: 0, width: 100, height: 50)
    textLayer.position = CGPoint(x: 50, y: 25)
    textLayer.opaque = true

    layer.addSublayer(textLayer)

    return cell
}

UPD：如果黑色背景不是你想要的，问题会变得有点棘手，但还是可以解决的。

UPD: If a black background is not what you are looking for, a problem becomes a bit trickier, but yet solvable.

您只需要在绘图机制中注入两行代码。有两种方法可以达到这个目的：

All you need is to inject two lines of code into drawing mechanism. There are two ways to achieve this:

• 使用委托 CALayer 或

创建 CATextLayer 。

在我们的案例中，我认为后者更可取。因此，在下面的示例中，不使用 CATextLayer ，而是使用此类：

In our case I believe the latter is preferable. So instead of CATextLayer in the example below use this class:

class OpaqueTextLayerWithCustomizableBackgroundColor: CATextLayer {
    override func drawInContext(ctx: CGContext) {
        if let color = backgroundColor {
            CGContextSetFillColorWithColor(ctx, color)
            CGContextFillRect(ctx, bounds);
        }
        super.drawInContext(ctx)
    }
}

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