点击'X'元素时触发UISearchBar和事件 [英] UISearchBar and event fired when 'X' element is tapped

问题描述

在UISearchBar上，有一个X元素，允许您一次清除所有内容。有没有办法在发生这种情况时收到通知？

On the UISearchBar, there's an X element that allows you to clear all of the contents at once. Is there a way to get notified when this happens?

UISearchBarDelegate :: searchBarCancelButtonClicked 仅在取消时触发按钮被点击。

UISearchBarDelegate::searchBarCancelButtonClicked is fired only when the "Cancel" button is tapped.

推荐答案

UISearchBar 没有委托此事件的方法。通过实现回调委托的 textDidChange：方法并检查空字符串，你几乎可以得到你想要的东西。

The UISearchBar doesn't have a delegate method for this event. You can nearly get what you want by implementing the textDidChange: method of the callback delegate and checking for an empty string.

我不推荐它，但还有另一种可能的方法。 UISearchBar 由UITextField组成，它有一个委托方法，当用户点击清除按钮时会调用该方法（ textFieldShouldClear：）。您可以通过遍历 UISearchBar 的子视图来获取 UITextField ：

I don't recommend it, but there is another possible way. The UISearchBar is composed of a UITextField, which does have a delegate method that is called when the user taps the clear button (textFieldShouldClear:). You can get the UITextField by traversing the UISearchBar's child views:

（这是在派生的 UISearchBar 类的上下文中）

(this is in the context of a derived UISearchBar class)

- (UIView*) textField
{
    for (UIView* v in self.subviews)
    {
        if ( [v isKindOfClass: [UITextField class]] )
            return v;
    }

    return nil;
}

从这里，你可以重新分配 UITextField 委托您自己的实现，注意将委托调用转发给旧委托。这样你就可以拦截 textFieldShouldClear：。或者，如果结果 UISearchBar 是 UITextField 的委托，它包含你可以调用textFieldShouldClear：。 ..不理想，但技术上可行。

from here, you could re-assign the UITextField delegate to your own implementation, taking care to forward delegate calls to the old delegate. This way you could intercept textFieldShouldClear:. Or if it turns out the UISearchBar is the delegate for the UITextField it contains you could swizzle the call to textFieldShouldClear:... Not ideal, clearly, but technically feasible.

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