Question

在UIWebView中，如果包含文本的输入元素具有焦点，并且按下按钮会导致输入失去焦点，则随后双击输入以重新获得焦点并选择剪切（或复制）显示的弹出栏中的“粘贴”或“粘贴”会导致UIWebView因错误而崩溃：

-[UIWebView cut:]: unrecognized selector sent to instance 0x10900ca60

演示项目：https://github.com/guarani/WebViewDoubleTapTestTests.git

我认为这必须是UIWebView错误，任何想法？

为了完整性，以下是我的网页视图的内容

<html>
    <head>
    </head>
    <body>
        <br><br>
        <input type="text">
        <input type="button">
    </body>
</html>

在Apple提交了一份错误报告：15894403

更新2019/05/30：iOS 12.0（16E226）中仍然存在错误

Answer 1

这是一个Apple bug。问题是响应者链中的cut:操作发送错误，最终被发送到UIWebView实例而不是实现该方法的内部UIWebDocumentView。

在Apple修复bug之前，让我们对Objective C运行时有一些乐趣。

在这里，我将UIWebView子类化为支持所有UIResponderStandardEditActions方法的目的，方法是将它们转发到正确的内部实例。

@import ObjectiveC;    

@interface CutCopyPasteFixedWebView : UIWebView @end

@implementation CutCopyPasteFixedWebView

- (UIView*)_internalView
{
    UIView* internalView = objc_getAssociatedObject(self, "__internal_view_key");

    if(internalView == nil && self.subviews.count > 0)
    {
        for (UIView* view in self.scrollView.subviews) {
            if([view.class.description hasPrefix:@"UIWeb"])
            {
                internalView = view;

                objc_setAssociatedObject(self, "__internal_view_key", view, OBJC_ASSOCIATION_ASSIGN);

                break;
            }
        }
    }

    return internalView;
}

void webView_implement_UIResponderStandardEditActions(id self, SEL selector, id param)
{
    void (*method)(id, SEL, id) = (void(*)(id, SEL, id))[[self _internalView] methodForSelector:selector];

    //Call internal implementation.
    method([self _internalView], selector, param);
}

- (void)_prepareForNoCrashes
{
    NSArray* selectors = @[@"cut:", @"copy:", @"paste:", @"select:", @"selectAll:", @"delete:", @"makeTextWritingDirectionLeftToRight:", @"makeTextWritingDirectionRightToLeft:", @"toggleBoldface:", @"toggleItalics:", @"toggleUnderline:", @"increaseSize:", @"decreaseSize:"];

    for (NSString* selName in selectors)
    {
        SEL selector = NSSelectorFromString(selName);

        //This is safe, the method will fail if there is already an implementation.
        class_addMethod(self.class, selector, (IMP)webView_implement_UIResponderStandardEditActions, "");
    }
}

- (void)awakeFromNib
{
    [self _prepareForNoCrashes];

    [super awakeFromNib];
}

@end

在故事板中使用此子类。

玩得开心。

Answer 2

如果您不介意没有剪切/粘贴等标注。在这种情况下，当UIWebview错误地成为第一响应者时，您也可以使用此类别修复它。这不禁止剪切/粘贴/等。当UIWebDocumentView（正确）成为第一响应者时。

@implementation UIWebView (NoWrongPerformWebview)

- (BOOL)canPerformAction:(SEL)action withSender:(id)sender
{
    return NO;
}

@end

// Swift 4兼容版

import UIKit

extension UIWebView {

    override open func canPerformAction(_ action: Selector, withSender sender: Any?) -> Bool {
        // Should be respond to a certain Selector ??
        return responds(to: action)
    }
}

Answer 3

如果有人有兴趣，这里是Leo Natans方法的快速版本：

import Foundation
import ObjectiveC

var AssociatedObjectHandle: UInt8 = 0


class CustomWebView: UIWebView {
    func _internalView() -> UIView? {
        var internalView:UIView? = objc_getAssociatedObject(self, "__internal_view_key") as? UIView
        if internalView == nil && self.subviews.count > 0 {
            for view: UIView in self.scrollView.subviews {
                if view.self.description.hasPrefix("UIWeb") {
                    internalView = view
                    objc_setAssociatedObject(self, "__internal_view_key", view, objc_AssociationPolicy.OBJC_ASSOCIATION_ASSIGN)
                }
            }
        }
        return internalView
    }

    override func awakeFromNib() {
        super.awakeFromNib()
        self._prepareForNoCrashes()
    }

    func _prepareForNoCrashes() {
        let selectors = ["cut:", "copy:", "paste:", "select:", "selectAll:", "delete:", "makeTextWritingDirectionLeftToRight:", "makeTextWritingDirectionRightToLeft:", "toggleBoldface:", "toggleItalics:", "toggleUnderline:", "increaseSize:", "decreaseSize:"]
        for selName: String in selectors {
            let selector = NSSelectorFromString(selName)
            //This is safe, the method will fail if there is already an implementation.
            let swizzledMethod:IMP = class_getInstanceMethod(CustomWebView.self, #selector(CustomWebView.webView_implement_UIResponderStandardEditActions))
            class_addMethod(CustomWebView.self, selector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod))
        }
    }

    func webView_implement_UIResponderStandardEditActions(this:AnyObject, selector:Selector, param:AnyObject)
    {
        let method = {(val1: UIView?, val2: Selector, val3: AnyObject) -> Void in
            self._internalView()?.methodForSelector(selector)
        }

        method(self._internalView(), selector, param);
    }

}

Answer 4

- (UIView *)_internalView {
    UIView *internalView = nil;

    if (internalView == nil && self.subviews.count > 0) {
        for (UIView *view in self.scrollView.subviews) {
            if([view.class.description hasPrefix:@"UIWeb"]) {
                internalView = view;
                break;
            }
        }
    }

    return internalView;
}

- (id)forwardingTargetForSelector:(SEL)aSelector {
    struct objc_method_description methodDescription = protocol_getMethodDescription(@protocol(UIResponderStandardEditActions), aSelector, NO, YES);

    if (methodDescription.name == aSelector) {
        UIView *view = [self _internalView];
        if ([view respondsToSelector:aSelector]) {
            return view;
        }
    }
    return [super forwardingTargetForSelector:aSelector];
}

UIWebView Bug： - [UIWebView cut：]：无法识别的选择器发送到实例

4 个答案: