在窗體頂部繪製圓形

Question

我有一個WinForms應用程序，我想以編程方式在某些區域頂部繪製圓圈。我遇到了幾個問題，任何見解都將不勝感激！

1）我有繪製和清除圓圈的代碼（見下面），但是圓圈被繪製在我所有的控件後面。我希望它們在每種情況下都被視爲「最高級」。我該怎麼做呢？

2）當我的應用程序啓動時，我會有一些需要馬上繪製的圈子。我試圖在Form Load事件上繪製它們無濟於事。但是在這裏（Form graphics not set when form loads）我現在正在繪製Paint事件。雖然這工作相當不錯（用一個布爾，以確保它只有它第一次），它似乎有問題this.Invalidate();（因爲沒有畫圈）。有沒有更好的辦法？這裏是我的代碼（parseText上具有ComboBox的指數變化運行）：

private void parseText() 
{ 
    this.Invalidate(); 
    List<string> lines = new List<string>(richTextBoxRaw.Text.Split(new string[] { Environment.NewLine}, StringSplitOptions.RemoveEmptyEntries)); 

    foreach (string s in lines) 
    { 
     switch (s) 
     { 
      case "<draw1>": 
       drawCircle(107, 26, 25); 
       break; 
      default: 
       break; 
     } 
    } 
} 

private void drawCircle(int x, int y, int transparency) 
{ 
    if (transparency < 0) 
     transparency = 0; 
    else if (transparency > 255) 
     transparency = 255; 

    SolidBrush brush = new SolidBrush(Color.FromArgb(transparency, 255,0,0)); 
    Graphics graphics = this.CreateGraphics(); 

    graphics.FillEllipse(brush, new Rectangle(x, y, 25, 25)); 
    brush.Dispose(); 
    graphics.Dispose(); 
} 

private void Form1_Paint(object sender, PaintEventArgs e) 
{ 
    if (starting) 
     parseText(); 

    starting = false; 
} 

Answer 1

一個不那麼複雜，但工作完成你的要求的方案可以作爲創建自定義的透明面板，並將其放置在頂部控制紅圈將被繪製的位置。

public partial class Form1 : Form 
{ 
    public Form1() 
    { 
     InitializeComponent(); 
    } 

    private void DrawCircle(int x, int y, int transparency, Graphics graphics) 
    { 
     if (transparency < 0) 
      transparency = 0; 
     else if (transparency > 255) 
      transparency = 255; 

     SolidBrush brush = new SolidBrush(Color.FromArgb(transparency, 255, 0, 0)); 

     graphics.FillEllipse(brush, new Rectangle(x, y, 25, 25)); 
     brush.Dispose(); 
     graphics.Dispose(); 
    } 

    private void TransparentPanel1_Paint(object sender, PaintEventArgs e) 
    { 
     DrawCircle(10, 10, 255, e.Graphics); 
    } 

    private void Form1_Load(object sender, EventArgs e) 
    { 
     transparentPanel1.Enabled = false; 
     transparentPanel1.Paint += TransparentPanel1_Paint; 
     transparentPanel1.BringToFront(); 
    } 
} 

public class TransparentPanel : Panel 
{ 
    protected override CreateParams CreateParams 
    { 
     get 
     { 
      CreateParams cp = base.CreateParams; 
      cp.ExStyle |= 0x00000020; // WS_EX_TRANSPARENT 
      return cp; 
     } 
    } 
    protected override void OnPaintBackground(PaintEventArgs e) 
    { 
     //base.OnPaintBackground(e); 
    } 
}