更改按鈕名稱與動態文本框事件處理程序

Question

我需要當按下鼠標右鍵單擊創建一個文本框在midle的按鈕。 當按下輸入鍵在我的文本框中改變按鈕名稱爲文本框給定文本;

這裏是我的代碼：

TextBox txt; 
private void c_MouseDown(object sender, MouseEventArgs e) 
    { 
    if (e.Button == MouseButtons.Right) 
     { 
      ss = sender as Button; 
      Point location = ss.Location; 
      int xLocation = ss.Location.X; 
      int yLocation = ss.Location.Y; 

      txt = new TextBox(); 
      txt.Name = "textBox1"; 
      txt.Text = "Add Text"; 

      txt.Location = new Point(xLocation - 10, yLocation + 20); 
      Controls.Add(txt); 
      txt.Focus(); 
      txt.BringToFront(); 

      txt.KeyDown += txt_KeyDown; 
     } 
    } 


    private void txt_KeyDown(object sender, KeyEventArgs e) 
    { 

     if (e.KeyCode == Keys.Enter) 
     { 
      ss = sender as Button; 
      ss.Name = txt.Text; 
     } 

    } 

我得到錯誤對象引用不設置到對象的實例。

Answer 1

一個解決這個問題的方法是在文本框的標籤屬性來保存對按鈕的引用：什麼是一個NullPointerException，以及如何解決呢]

TextBox txt; 
private void c_MouseDown(object sender, MouseEventArgs e) 
{ 
if (e.Button == MouseButtons.Right) 
    { 
     ss = sender as Button; 
     Point location = ss.Location; 
     int xLocation = ss.Location.X; 
     int yLocation = ss.Location.Y; 

     txt = new TextBox(); 
     txt.Name = "textBox1"; 
     txt.Text = "Add Text"; 
     txt.Tag = ss; 

     txt.Location = new Point(xLocation - 10, yLocation + 20); 
     Controls.Add(txt); 
     txt.Focus(); 
     txt.BringToFront(); 

     txt.KeyDown += txt_KeyDown; 
    } 
} 


private void txt_KeyDown(object sender, KeyEventArgs e) 
{ 

    if (e.KeyCode == Keys.Enter) 
    { 
     ss = (sender as TextBox).Tag as Button; 
     ss.Name = txt.Text; 
     Controls.Remove(txt); 
    } 

}