引发 NSUncaughtExceptionHandler 异常

Question

我想测试NSUncaughtExceptionHandler 的实现。我试过的：

int[] array = new int[3];
array[4] = 1;

object o = null;
o.GetHashCode();

这是我在 AppDelegate.cs 中的实现：

public delegate void NSUncaughtExceptionHandler(IntPtr handle);
[DllImport("/System/Library/Frameworks/Foundation.framework/Foundation")]
private static extern void NSSetUncaughtExceptionHandler(IntPtr handle);

public override bool FinishedLaunching(UIApplication app, NSDictionary options)
{
    global::Xamarin.Forms.Forms.Init();
    LoadApplication(new App());

    NSSetUncaughtExceptionHandler(Marshal.GetFunctionPointerForDelegate(new NSUncaughtExceptionHandler(MyUncaughtExceptionHandler)));

    return base.FinishedLaunching(app, options);
}

[MonoPInvokeCallback(typeof(NSUncaughtExceptionHandler))]
private static void MyUncaughtExceptionHandler(IntPtr handle)
{
    NSException exception = (NSException)ObjCRuntime.Runtime.GetNSObject(handle);

}

异常未被捕获。如何引发 NSUncaughtExceptionHandler 可以捕获的异常？

Answer 1

现实世界的例外情况如何：NSInvalidArgumentException（由于无法识别的选择器）

声明消息发送签名：

[DllImport(Constants.ObjectiveCLibrary, EntryPoint = "objc_msgSend")]
static extern CGSize cgsize_objc_msgSend_IntPtr_float_int_foobar(IntPtr target, IntPtr selector, IntPtr font, nfloat width, UILineBreakMode mode);

异常处理：

[MonoPInvokeCallback(typeof(NSUncaughtExceptionHandler))]
private static void MyUncaughtExceptionHandler(IntPtr handle)
{
    NSException exception = (NSException)ObjCRuntime.Runtime.GetNSObject(handle);
    Console.WriteLine(exception);
    Console.WriteLine(exception.CallStackSymbols[0]);
}

进行有效和无效调用：

    public override bool FinishedLaunching(UIApplication application, NSDictionary launchOptions)
    {
        // Override point for customization after application launch.
        // If not required for your application you can safely delete this method
        NSSetUncaughtExceptionHandler(Marshal.GetFunctionPointerForDelegate(new NSUncaughtExceptionHandler(MyUncaughtExceptionHandler)));

NSString target = new NSString("StackOverFlow");
Selector selector = new Selector("sizeWithFont:forWidth:lineBreakMode:");
UIFont font = null;
nfloat width = 1.0f;
UILineBreakMode mode = UILineBreakMode.CharacterWrap;
CGSize size = cgsize_objc_msgSend_IntPtr_float_int_foobar( target.Handle, selector.Handle, font == null ? IntPtr.Zero : font.Handle, width, mode);

// `NSInvalidArgumentException` (due to unrecognized selector)
selector = new Selector("StackOverFlowSelector:");
size = cgsize_objc_msgSend_IntPtr_float_int_foobar(target.Handle, selector.Handle, font == null ? IntPtr.Zero : font.Handle, width, mode);

return true;

}

输出：

-[__NSCFString StackOverFlowSelector:]: unrecognized selector sent to instance 0x7cb0a4e0
0   CoreFoundation                      0x00976494 __exceptionPreprocess + 180

注意：

请记住，您正在回调 ma​​naged 代码以捕获 unmanaged 异常，这确实应该在 ObjC 库中完成..