C++ Builder，TShapes，如何更改顏色OnMouseEnter

Question

Hej！我試圖以編程方式創建TShape。當我運行程序並單擊按鈕時 - 一切正常。但是當我再次點擊按鈕時，事件OnMouseEnter（OnMouseLeave）只能與最後一個形狀一起使用。不適用於任何以前的。

int i=0; 
    TShape* Shape[50]; 
    void __fastcall TForm1::Button1Click(TObject *Sender) 
{ 
    int aHeight = rand() % 101 + 90; 
    int bWidth = rand() % 101 + 50; 
    i++; 
    Shape[i] = new TShape(Form1); 
    Shape[i]->Parent = this; 
    Shape[i]->Visible = true; 
    Shape[i]->Brush->Style=stCircle; 
    Shape[i]->Brush->Color=clBlack; 

    Shape[i]->Top = aHeight; 
    Shape[i]->Left = bWidth; 
    Shape[i]->Height=aHeight; 
    Shape[i]->Width=bWidth; 

    Shape[i]->OnMouseEnter = MouseEnter; 
    Shape[i]->OnMouseLeave = MouseLeave; 

    Label2->Caption=i; 


    void __fastcall TForm1::MouseEnter(TObject *Sender) 
{ 
    Shape[i]->Pen->Color = clBlue; 
    Shape[i]->Brush->Style=stSquare; 
    Shape[i]->Brush->Color=clRed; 
} 



void __fastcall TForm1::MouseLeave(TObject *Sender) 
{ 
    Shape[i]->Pen->Color = clBlack; 
    Shape[i]->Brush->Style=stCircle; 
    Shape[i]->Brush->Color=clBlack; 
} 

Answer 1

你OnMouse...事件處理程序使用i索引到Shape[]陣列，但i包含的指數最後TShape你創建（BTW，你是不是填充Shape[0]米因爲您之前遞增i創建第一個TShape）。

要你嘗試，事件處理程序需要使用他們Sender參數知道哪些TShape是目前觸發每個事件，比如什麼：

TShape* Shape[50]; 
int i = 0; 

void __fastcall TForm1::Button1Click(TObject *Sender) 
{ 
    ... 

    Shape[i] = new TShape(this); 
    Shape[i]->Parent = this; 
    ... 
    Shape[i]->OnMouseEnter = MouseEnter; 
    Shape[i]->OnMouseLeave = MouseLeave; 

    ++i; 
    Label2->Caption = i; 
} 

void __fastcall TForm1::MouseEnter(TObject *Sender) 
{ 
    TShape *pShape = static_cast<TShape*>(Sender); 

    pShape->Pen->Color = clBlue; 
    pShape->Brush->Style = stSquare; 
    pShape->Brush->Color = clRed; 
} 

void __fastcall TForm1::MouseLeave(TObject *Sender) 
{ 
    TShape *pShape = static_cast<TShape*>(Sender); 

    pShape->Pen->Color = clBlack; 
    pShape->Brush->Style = stCircle; 
    pShape->Brush->Color = clBlack; 
}