overriding

问题 Consider the following program: class A { __host__ __device__ void foo(); }; class B : A { __host__ void foo(); }; int main() { A a; (void) a; B b; (void) b; } This compiles (GodBolt) with nvcc 10. Yet, in more complex programs, I sometimes get the following error (line breaks for readability): whatever.hpp(88): error: execution space mismatch: overridden entity (function "C::foo") is a __host__ __device__ function, but overriding entity (function "D::foo") is a __host__ function So, nvcc is

问题 I've read many threads with questions which looks like questions I am going to ask. However, I can not find satisfactory answers which could be applied to my questions, since there are more than one fold in my questions, seperated in three aspects. This is the interface SubtitleDecoderFactory in https://github.com/google/ExoPlayer/blob/release-v2/library/core/src/main/java/com/google/android/exoplayer2/text/SubtitleDecoderFactory.java As I understand, an interace is abstraction and can not

问题 I have overridden WndProc in UserControl level to detect MouseDown, MouseUp, and MouseMove to any Control added in that UserControl. protected override void WndProc(ref Message m) { Point mouseLoc = new Point(); switch (m.Msg) { case WM_LBUTTONDOWN: System.Diagnostics.Debug.WriteLine("mouse down"); //this.OnMouseDown(new MouseEventArgs(MouseButtons.Left, 1, mouseLoc.X, mouseLoc.Y, 0)); break; case WM_LBUTTONUP: System.Diagnostics.Debug.WriteLine("mouse up"); //this.OnMouseDown(new

问题 I'm trying to come to grips with the onSaveInstanceState method in class View (not the one in class Activity). That method does return a Parcelable. I derived my own View from ViewGroup and overrode that method to save my own state. But when the state was to be saved I got an exception: java.lang.IllegalStateException: Derived class did not call super.onSaveInstanceState() That is true enough, but simply calling that method doesn't seem enough to me. So how should I do this? If the method

问题 I'm trying to come to grips with the onSaveInstanceState method in class View (not the one in class Activity). That method does return a Parcelable. I derived my own View from ViewGroup and overrode that method to save my own state. But when the state was to be saved I got an exception: java.lang.IllegalStateException: Derived class did not call super.onSaveInstanceState() That is true enough, but simply calling that method doesn't seem enough to me. So how should I do this? If the method

问题 I want to override the home button in my android activity. I have tried out few things related to this which are working for 2.3 and below but not for 4.0 above @Override public boolean onKeyDown(int keyCode, KeyEvent event) { if(keyCode == KeyEvent.KEYCODE_HOME) { startActivity(new Intent(this, ActivityB.class)); return true; } return super.onKeyDown(keyCode, event); } and other is way @Override public void onAttachedToWindow() { this.getWindow().setType(WindowManager.LayoutParams.TYPE

问题 I want to override the home button in my android activity. I have tried out few things related to this which are working for 2.3 and below but not for 4.0 above @Override public boolean onKeyDown(int keyCode, KeyEvent event) { if(keyCode == KeyEvent.KEYCODE_HOME) { startActivity(new Intent(this, ActivityB.class)); return true; } return super.onKeyDown(keyCode, event); } and other is way @Override public void onAttachedToWindow() { this.getWindow().setType(WindowManager.LayoutParams.TYPE

问题 I want to override the home button in my android activity. I have tried out few things related to this which are working for 2.3 and below but not for 4.0 above @Override public boolean onKeyDown(int keyCode, KeyEvent event) { if(keyCode == KeyEvent.KEYCODE_HOME) { startActivity(new Intent(this, ActivityB.class)); return true; } return super.onKeyDown(keyCode, event); } and other is way @Override public void onAttachedToWindow() { this.getWindow().setType(WindowManager.LayoutParams.TYPE

问题 This is not about "When VTABLE is created?". Rather, when the VPTR should be initialized? Is it at the beginning/end of the constructor or before/after the constructor? A::A () : i(0), j(0) -->> here ? { -->> here ? //... -->> here ? } 回答1: The machinery for virtual calls (usually a v-table, but doesn't need to be) is set up during the ctor-initializer , after construction of base subobjects and before construction of members. Section [class.base.init] decrees: Member functions (including

问题 As I understand it, the override keyword states that a given declaration implements a base virtual method, and the compilation should fail if there is no matching base method found. My understanding of the final keyword is that it tells the compiler that no class shall override this virtual function. So is override final redundant? It seems to compile fine. What information does override final convey that final does not? What is the use case for such a combination? 回答1: final does not require