Access violation when assigning a value to my component Bitmap property [closed]

问题

It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.

Closed 7 years ago.

I'm trying to create a component that must use a Bitmap, I'm having a problem when I go to select the image on the property.

Here is an excerpt of the code: Property Declaration

Property StarOff: TBitmap read FStarOff write SetStarOff;

Function SetStarOff

procedure TNotas.SetStarOff(const Value: TBitmap);
begin
FStarOff.Assign(Value);
end;

But, when I assign a value to the property, I get the error:

Access violation at address 1BC324B8 in module 'TNte.bpl'. Read of address 000000000

Why is this happening?

回答1:

Your setter method looks correct, but you're getting an Access Violation because your FStarOff member is nil at the moment.

The usual is to create it at construction time and free it at destruction time.

constructor TMyComponent.Create(AOwner: TComponent);
begin
  inherited;
  FStarOff := TBitmap.Create;
end;

destructor TMyComponent.Destroy;
begin
  FStarOff.Free;
  inherited;
end;

来源：https://stackoverflow.com/questions/13494829/access-violation-when-assigning-a-value-to-my-component-bitmap-property