objective-c - 使用 contentScaleFactor 属性缩放 UITextView

Question

我正在尝试为 UIView 创建更高分辨率的图像，特别是 UITextView。

这个问题和答案正是我想弄清楚的:

• Retain the resolution of the label after scaling in iphone

但是，当我这样做时，我的文本仍然模糊:

self.view.transform = CGAffineTransformMakeScale(2.f, 2.f);
[myText setContentScaleFactor:2.f]; // myText is a subview of self.view object

我也在 Apple 示例项目“UICatalog”中对 UILabel 进行了同样的尝试，它也很模糊。

我不明白为什么它对另一个问题对 Warrior 有用，对我却不起作用。我会在那里问 — 但我似乎无法在那里发表评论或提问。

Answer 1

设置 contentScaleFactor 和 contentsScale 实际上是关键，正如@dbotha 指出的那样，但是您必须分别遍历 View 和图层层次结构才能到达每个实际执行文本渲染的内部 CATiledLayer。添加屏幕比例也可能有意义。

所以正确的实现应该是这样的:

- (void)updateForZoomScale:(CGFloat)zoomScale {
    CGFloat screenAndZoomScale = zoomScale * [UIScreen mainScreen].scale;
    // Walk the layer and view hierarchies separately. We need to reach all tiled layers.
    [self applyScale:(zoomScale * [UIScreen mainScreen].scale) toView:self.textView];
    [self applyScale:(zoomScale * [UIScreen mainScreen].scale) toLayer:self.textView.layer];
}

- (void)applyScale:(CGFloat)scale toView:(UIView *)view {
    view.contentScaleFactor = scale;
    for (UIView *subview in view.subviews) {
        [self applyScale:scale toView:subview];
    }
}

- (void)applyScale:(CGFloat)scale toLayer:(CALayer *)layer {
    layer.contentsScale = scale;
    for (CALayer *sublayer in layer.sublayers) {
        [self applyScale:scale toLayer:sublayer];
    }
}