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[英]Issue regarding the cast from a float matrix to a Java.Lang.Object using C# (Xamarin development environment)
[英]How to cast C# interface to Java.Lang.Object?
目前,我正在Xamarin上开发IEGL10。 我已经实现了ISurfaceHolderCallback
并且在SurfaceCreated(ISurfaceHolder holder)
我必须调用这样的方法。
public void SurfaceCreated(ISurfaceHolder holder)
{
mEglSurface = mEgl.EglCreateWindowSurface(mEglDisplay, mEglConfig,
holder, null);
}
问题是,持有人是C#接口,EglCreateWindowSurface需要Java.Lang.Object。 那我该如何铸造。 如果我直接转换(Java.Lang.Object)holder
。 它抛出无效的强制转换异常。 请帮助我真的被困在这里的人。
如何将C#接口转换为Java.Lang.Object?
MonoDroid
为此目的集成了扩展:
Java.Lang.Object holder_object = holder.JavaCast<Java.Lang.Object>();
EGLSurface mEglSurface = mEgl.EglCreateWindowSurface(mEglDisplay, mEglConfig, holder_object, null);
您可以看到该文档:
public static class Extensions
{
//
// Summary:
// /// Performs an Android runtime-checked type conversion. ///
//
// Parameters:
// instance:
// /// An Android.Runtime.IJavaObject instance to convert /// to a TResult instance.
// ///
//
// Type parameters:
// TResult:
// /// The type to convert instance to. /// TResult must implement the /// Android.Runtime.IJavaObject
// interface. ///
//
// Returns:
// /// A TResult representation for /// instance. ///
//
// Exceptions:
// T:System.ArgumentException:
// ///
// /// The JNI class for TResult cannot be found. ///
// ///
// -or-
// ///
// /// The proxy class for TResult is /// abstract, and the non-abstract Proxy can't
// be found. ///
// ///
//
// T:System.InvalidCastException:
// /// The Anrdroid object instance instance.Handle /// cannot be converted to the
// Android type corresponding to /// TResult. ///
//
// T:System.NotSupportedException:
// /// An unknown error occurred. ///
//
// Remarks:
// /// /// This is a hack, but a currently necessary one. /// ///
// /// Most of the Android types are staticly generated /// wrappers over a description
// of the underlying Android types. This /// intermediate description does not expose
// implementation details, /// which sometimes must be relied upon. ///
// ///
// /// For example, consider the /// Javax.Microedition.Khronos.Egl.EGLContext.EGL
// /// property, which returns an instance of the /// Javax.Microedition.Khronos.Egl.IEGL
// /// interface. This interface is useless, containing no members to /// invoke
// or use. The developer is instead expected to convert this /// instance to an
// interface which contains actual operations, such as /// the Javax.Microedition.Khronos.Egl.IEGL10
// interface. /// Unfortunately, the MonoDroid-generated wrappers do not know this,
// /// nor can they (the EGL10 implementation may be removed in a /// future Android
// version). The result is that if developers attempt /// to cast within managed
// code, the result will be a /// System.InvalidCastException: ///
// /// EGL10 egl10 = (EGL10) EGLContext.EGL; // throws ///
// /// The JavaCast() method allows performing such type conversions /// while bypassing
// the managed type system and instead relying upon /// the Android runtime system
// to perform the type checking. This /// allows: ///
// /// EGL10 egl10 = EGLContext.EGL.JavaCast<EGL10>(); // good ///
public static TResult JavaCast<TResult>(this IJavaObject instance) where TResult : class, IJavaObject;
}
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