Xamarin表单-IOS:如何检测已更改的UIView大小 [英] Xamarin Form - IOS: How to detect the UIView size changed
问题描述
我使用ContentView创建了Xamarin Form,并为Android创建了渲染器.现在,我必须为IOS创建一个渲染器.
I created a Xamarin Form using ContentView and created a renderer for Android. Now I have to create a renderer for IOS.
在android渲染器中,我可以覆盖onSizeChanged并将那些宽度/高度值传递给自定义xamarin-form视图.
In android renderer, I can override onSizeChanged and passing those width/height value to the custom xamarin-form view.
protected override void OnSizeChanged(int w, int h, int oldw, int oldh) {
base.OnSizeChanged(w,h, oldw, old);
Element.SizChanged(w,h);
}
IOS中的UIView是否具有类似的方法来覆盖?我尝试覆盖Frame属性并在Element.SizeChanged(w,h)中调用,但是我将获得TargetInvocationException.
Does UIView in IOS has the similar method to override? I have tried override the Frame property and invoke in Element.SizeChanged(w,h), but I will get TargetInvocationException.
P.S. SizeChanged方法是我的自定义虚拟方法,而不是android方法.
P.S. SizeChanged method is my custom virtual method not android method.
推荐答案
覆盖LayoutSubviews
通常用于跟踪调整大小的事件,因为UIView
还要负责其所有子视图.
Overriding LayoutSubviews
is normally used to track resize events as a UIView
is responsible to for all of it's subviews also.
根据我在做什么以及该视图包含的内容,我也倾向于覆盖Bounds
和Frame
...根据父级,该视图的LayoutSubviews
可以称为很多...
I tend to also override Bounds
and Frame
depending upon what I am doing and what this view contains... Depending upon the parent, the View's LayoutSubviews
can be called a lot...
假设一个UIView子类如下:
Assuming a UIView subclass like:
public class UIViewResizing : UIView
{
public UIViewResizing() { }
public UIViewResizing(CGRect frame) : base(frame) { }
public UIViewResizing(NSCoder coder) : base(coder) { }
public override CGRect Bounds
{
get
{
return base.Bounds;
}
set
{
if (value != base.Bounds)
{
Console.WriteLine($"Bounds changing: {this}");
}
base.Bounds = value;
}
}
public override CGRect Frame
{
get
{
return base.Frame;
}
set
{
if (value != base.Frame)
{
Console.WriteLine($"Frame changing: {this}.");
}
base.Frame = value;
}
}
public override void LayoutSubviews()
{
Console.WriteLine($"LayoutSubViews requested: {this}");
base.LayoutSubviews();
}
}
行使:
var view = new UIViewResizing(new CGRect(100, 100, 100, 100));
view.BackgroundColor = UIColor.Red;
Add(view);
await Task.Delay(2500);
view.Frame = new CGRect(100, 100, 200, 200);
await Task.Delay(2500);
view.Bounds = new CGRect(20, 20, 100, 200);
结果:
Frame changing: <uiviewresize_UIViewResizing: 0x79a6cc00; frame = (-50 -50; 100 100); layer = <CALayer: 0x78628230>>.
LayoutSubViews requested: <uiviewresize_UIViewResizing: 0x79a6cc00; frame = (100 100; 100 100); layer = <CALayer: 0x78628230>>
Frame changing: <uiviewresize_UIViewResizing: 0x79a6cc00; frame = (100 100; 100 100); layer = <CALayer: 0x78628230>>.
LayoutSubViews requested: <uiviewresize_UIViewResizing: 0x79a6cc00; frame = (100 100; 200 200); layer = <CALayer: 0x78628230>>
Bounds changing: <uiviewresize_UIViewResizing: 0x79a6cc00; frame = (100 100; 200 200); layer = <CALayer: 0x78628230>>
LayoutSubViews requested: <uiviewresize_UIViewResizing: 0x79a6cc00; frame = (150 100; 100 200); layer = <CALayer: 0x78628230>>
请咨询该SO以获取更多信息:是否有UIView调整大小事件?
Consult this SO for additional information: Is there a UIView resize event?
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