Question

我正在使用链接中引入的UIWebView和 JSExport 构建应用： https://www.bignerdranch.com/blog/javascriptcore-example/

MyConsole代码：

@objc protocol ConsoleJSExports : JSExport {
    static func log(message: String) -> Void
    static func error(message: String) -> Void
}

@objc public class MyConsole : NSObject, ConsoleJSExports {

public class func log(message: String) {
    print("JS Log:\(message)")
}

public class func error(message: String) {
    print("JS Error:\(message)")
}

MyClass代码：

extension MyClass: UIWebViewDelegate {
    func webView(webView: UIWebView, shouldStartLoadWithRequest request: NSURLRequest, navigationType: UIWebViewNavigationType) -> Bool {
        return true
    }

    func webViewDidFinishLoad(webView: UIWebView) {
        weak var context = webView!.valueForKeyPath("documentView.webView.mainFrame.javaScriptContext") as? JSContext
        context?.setObject(MyConsole.self, forKeyedSubscript: "console")
    }

}

此应用程序运行正常，但在我将其删除并多次启动后，当我再次尝试访问webView的上下文时，它会崩溃：

func initMyJSCode(myId: String, rootUrl: String) {
    let context = webView.valueForKeyPath("documentView.webView.mainFrame.javaScriptContext") as! JSContext
    context.objectForKeyedSubscript("initMyJSCode").callWithArguments([myId, rootUrl])
}

我遇到错误：

Exception Type:  EXC_BAD_ACCESS (SIGSEGV)
Exception Subtype: KERN_INVALID_ADDRESS at 0x000000010a58beb8
Triggered by Thread:  6
Thread 0 name:  Dispatch queue: com.apple.main-thread
Thread 0:
0   JavaScriptCore                  0x00000001832f36b8 JSC::BytecodeGenerator::BytecodeGenerator(JSC::VM&, JSC::FunctionBodyNode*, JSC::UnlinkedFunctionCodeBlock*, JSC::DebuggerMode, JSC::ProfilerMode) + 4712
1   JavaScriptCore                  0x00000001832f32d4 JSC::BytecodeGenerator::BytecodeGenerator(JSC::VM&, JSC::FunctionBodyNode*, JSC::UnlinkedFunctionCodeBlock*, JSC::DebuggerMode, JSC::ProfilerMode) + 3716
2   JavaScriptCore                  0x0000000183595250 JSC::UnlinkedFunctionExecutable::codeBlockFor(JSC::VM&, JSC::SourceCode const&, JSC::CodeSpecializationKind, JSC::DebuggerMode, JSC::ProfilerMode, bool, JSC::ParserError&) + 468
3   JavaScriptCore                  0x00000001833e8794 JSC::ScriptExecutable::newCodeBlockFor(JSC::CodeSpecializationKind, JSC::JSFunction*, JSC::JSScope**, JSC::JSObject*&) + 628
4   JavaScriptCore                  0x00000001833e8d40 JSC::ScriptExecutable::prepareForExecutionImpl(JSC::ExecState*, JSC::JSFunction*, JSC::JSScope**, JSC::CodeSpecializationKind) + 120
5   JavaScriptCore                  0x00000001831d10bc JSC::LLInt::setUpCall(JSC::ExecState*, JSC::Instruction*, JSC::CodeSpecializationKind, JSC::JSValue, JSC::LLIntCallLinkInfo*) + 600
6   JavaScriptCore                  0x000000018350204c llint_entry + 24636
7   JavaScriptCore                  0x0000000183502058 llint_entry + 24648
8   JavaScriptCore                  0x0000000183502058 llint_entry + 24648
9   JavaScriptCore                  0x0000000183502058 llint_entry + 24648
10  JavaScriptCore                  0x0000000183502058 llint_entry + 24648
11  JavaScriptCore                  0x0000000183502058 llint_entry + 24648
12  JavaScriptCore                  0x0000000183502058 llint_entry + 24648
13  JavaScriptCore                  0x0000000183502058 llint_entry + 24648
14  JavaScriptCore                  0x0000000183502058 llint_entry + 24648
15  JavaScriptCore                  0x0000000183502058 llint_entry + 24648
16  JavaScriptCore                  0x0000000183502058 llint_entry + 24648
17  JavaScriptCore                  0x0000000183502058 llint_entry + 24648
18  JavaScriptCore                  0x0000000183502058 llint_entry + 24648
19  JavaScriptCore                  0x00000001834fbdf0 callToJavaScript + 304
20  JavaScriptCore                  0x000000018346a454 JSC::JITCode::execute(JSC::VM*, JSC::ProtoCallFrame*) + 44
21  JavaScriptCore                  0x00000001831d5554 JSC::Interpreter::executeCall(JSC::ExecState*, JSC::JSObject*, JSC::CallType, JSC::CallData const&, JSC::JSValue, JSC::ArgList const&) + 416
22  JavaScriptCore                  0x00000001831d52e0 JSObjectCallAsFunction + 556
23  JavaScriptCore                  0x00000001834d8964 -[JSValue callWithArguments:] + 288

有人可以帮忙吗？

Answer 1

我发现从UIWebView获取JSContext并不是一个好主意。由于它不是公共API，因此无法保证在运行时始终可以访问JSContext。

在UIWebView中访问JSContext时的EXC_BAD_ACCESS

1 个答案: