Question

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？

UISearchBarDelegate::searchBarCancelButtonClicked仅在点击“取消”按钮时被触发。

Answer 1

UISearchBar没有此事件的委托方法。通过实现回调委托的textDidChange:方法并检查空字符串，您几乎可以获得所需的内容。

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

（这是在派生的UISearchBar类的上下文中）

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

    return nil;
}

从这里，您可以将UITextField委托重新分配给您自己的实现，注意将委托调用转发给旧委托。这样你就可以拦截textFieldShouldClear:。或者如果事实证明UISearchBar是它所包含的UITextField的委托，你可以调用textFieldShouldClear：......不理想，但技术上可行。

Answer 2

我遇到了同样的问题，我使用此功能解决了这个问题。

- (void)searchBar:(UISearchBar *)searchBar textDidChange:(NSString *)searchText 
{
    // This method has been called when u enter some text on search or Cancel the search.
    if([searchText isEqualToString:@""] || searchText==nil) {
        // Nothing to search, empty result.

       [UIView animateWithDuration:0.2 animations:^ {
        //Reposition search bar 
        [_searchBar setFrame:CGRectMake(230, 26, 43, 44)];
        [_searchBar setNeedsLayout];
       }];
    }
}

Answer 3

以上是上一个问题的答案，这应该完全符合您的要求。 UISearchbar clearButton forces the keyboard to appear

Answer 4

这是“Method Swizzling”解决方案。

创建UISearchBar的新类别。此类别在运行时在-(BOOL)textFieldShouldClear:(UITextField *)textField;和-(BOOL)jbm_textFieldShouldClear:(UITextField *)textField之间创建一个新方法和混合方法。
自定义UISearchBarDelegate的新协议，以便添加新方法- (void)searchBarClearButtonClicked:(id)sender;

的UISearchBar + JMBTextFieldControl.h

    @protocol UISearchBarWithClearButtonDelegate <UISearchBarDelegate>
    @optional
    - (void)searchBarClearButtonClicked:(id)sender;
    @end

    @interface UISearchBar (JMBTextFieldControl)
    @end

的UISearchBar + JMBTextFieldControl.m

    #import "UISearchBar+JMBTextFieldControl.h"
    #import <objc/runtime.h>

    @implementation NSObject (Swizzling)

    + (void)brc_swizzleMethod:(SEL)origSelector withMethod:(SEL)newSelector
    {
        Method origMethod = class_getInstanceMethod(self, origSelector);
        Method newMethod = class_getInstanceMethod(self, newSelector);

        if(class_addMethod(self, origSelector, method_getImplementation(newMethod), method_getTypeEncoding(newMethod)))
            class_replaceMethod(self, newSelector, method_getImplementation(origMethod), method_getTypeEncoding(origMethod));
        else
            method_exchangeImplementations(origMethod, newMethod);
    }
    @end

    @implementation UISearchBar (JMBTextFieldControl)

    + (void)load {
        [self brc_swizzleMethod:@selector(textFieldShouldClear:) withMethod:@selector(jbm_textFieldShouldClear:)];
    }

    - (id<UISearchBarWithClearButtonDelegate>)jbm_customDelegate {
        if( [[self delegate] conformsToProtocol:@protocol(UISearchBarWithClearButtonDelegate)] )
            return (id<UISearchBarWithClearButtonDelegate>)[self delegate];
        else
            return nil;
    }

    - (BOOL)jbm_textFieldShouldClear:(UITextField *)textField
    {
        if ( [[self jbm_customDelegate] respondsToSelector:@selector(searchBarClearButtonClicked:)] )
            [[self jbm_customDelegate] searchBarClearButtonClicked:self];

        return [self jbm_textFieldShouldClear:textField];
    }

    @end

参考

Dave DeLong - How to add a method to an existing protocol in Cocoa?
Nikolay Vlasov - CCBottomRefreshControl

点击'X'元素时触发UISearchBar和事件

4 个答案: