在 WKWebView 中操作粘贴内容

我需要操作粘贴到 WKWebView（从任何源）中的文本，运行可能需要一些时间的异步操作。

我最初的想法是使用 Javascript 和 WKWebView 配置来获取onpaste event:

WKUserContentController *wkUController = [[WKUserContentController alloc] init];

NSString *pasteJSSource = @"document.addEventListener('onpaste', function(){ window.webkit.messageHandlers.ComposerListener.postMessage('onpaste happened!'); })";

WKUserScript *pasteScript = [[WKUserScript alloc] initWithSource:pasteJSSource injectionTime:WKUserScriptInjectionTimeAtDocumentEnd forMainFrameOnly: NO];

[wkUController addScriptMessageHandler:self name:@"ComposerListener"];

[wkUController addUserScript:pasteScript];

webViewConfiguration.userContentController = wkUController;

然后我的班级实现了WKScriptMessageHandler

#pragma mark - WKScriptMessageHandler

- (void)userContentController:(WKUserContentController *)userContentController didReceiveScriptMessage:(WKScriptMessage *)message
{
    NSLog(@"message: %@", message.body);
}

（忽略Obj-c，swift也可以）

但我有两个问题：

1. userContentController:didReceiveScriptMessage:从未被调用过
2. 我不知道如何拦截粘贴的代码并将其替换为不同的代码

关于如何解决这个问题的任何想法（即使没有 JS，我显然不知道：P）？ 谢谢。

为了后代：

我确信有一种使用 JS 的方法可以做到这一点并且更干净，但我设法使用方法 swizzling 实现了结果：

//Method Swizzling
UIView *webContentView = self.webView.contentView;
if(webContentView != nil)
{
    //Paste:
    NSError *error;
    [webContentView swizzleMethod:@selector(paste:) withSelector:@selector(my_paste:) error:&error];
    if(error != nil)
    {
        NSLog("Failed to swizzle 'paste:' into WKContentView: %@, error);
        NSAssert(false, error);
    }

    ...
}

其中 contentView 是：

- (UIView *)contentView
{
    return [self subviewWithClassName:@"WKContentView"];
}

方法my_paste:需要成为 UIResponder 的一部分（由私有 WKContentView 实现）

#pragma mark - Method Swizzling UIResponder

@interface UIResponder (WebComposerSwizzling)

- (void)my_paste:(id)sender;
#define original_paste my_paste

@end

@implementation UIResponder (WebComposerSwizzling)

- (void)my_paste:(id)sender
{
    MailComposerViewController* strongComposer = sCurrentComposer;
    if (strongComposer)
        [strongComposer manipulatePasteboard:nil];
    [self original_paste:sender];
}

@end

注意sCurrentComposer是我的 ViewController 中的静态变量

__weak MailComposerViewController* sCurrentComposer;

各种实用程序：

UIView+SubviewSearch

import UIKit

extension UIView {

    /// Find a subview corresponding to the className parameter, recursively.
    @objc public func subviewWithClassName(_ className: String) -> UIView? {
        if NSStringFromClass(type(of: self)) == className {
            return self
        } else {
            for subview in subviews {
                return subview.subviewWithClassName(className)
            }
        }
        return nil
    }
}

NSObject+Swizzling

import Foundation

extension NSObject {

    enum NSObjectSwizzlingError: Error {
        case originalSelectorNotFound
    }

    @objc public func swizzleMethod(_ currentSelector: Selector, withSelector newSelector: Selector) throws {
        if let currentMethod = self.instanceMethod(for: currentSelector),
            let newMethod = self.instanceMethod(for:newSelector) {
            method_exchangeImplementations(currentMethod, newMethod)
        } else {
            throw NSObjectSwizzlingError.originalSelectorNotFound
        }
    }

    @objc public func instanceMethod(for selector: Selector) -> Method? {
        let classType: AnyClass! = object_getClass(self)
        return class_getInstanceMethod(classType, selector)
    }
}

（我对 Swift OBJ-C 混合感到抱歉）