確定按下「Backspace」按鈕

Question

如何確定用戶按下的GWT 退格鍵按鈕？我想這一點，但它不工作

@Override 
    public void onKeyPress(KeyPressEvent event) { 
     char charCode= event.getCharCode(); 
     if(charCode == (char) KeyCodes.KEY_BACKSPACE){ 
      //do someThing 
     } 
    } 

Answer 1

的keypress事件在大多數瀏覽器作爲唯一射擊時的字符將產生執行（這就是它如何被標準化：http://www.w3.org/TR/DOM-Level-3-Events/#event-type-keypress）。退格顯然不會產生一個字符;你應該使用​​或keyup來檢測它。

Answer 2

@Override 
public void onKeyPress(KeyPressEvent event) { 
    char charCode= event.getCharCode(); 
    if(charCode == (char) KeyEvent.VK_BACK_SPACE){ 
     //do someThing 
    } 
} 

Answer 3

@Override 
    public void onKeyPress(KeyUpEvent event) { 
     char charCode= keyUpEvent.getNativeKeyCode(); 
     if(charCode == (char) KeyCodes.KEY_BACKSPACE){ 
      //do someThing 
    } 

Answer 4

你可以從完全不同的角度去想它，只是跟蹤字符串的長度進入了一個文本框或任何你想抓住從文本：

 // Global variable to save previous String data 
     String stringEntered = ""; 

     // Our TextBox 
     TextBox textBox = new TextBox(); 

     @Override 
     public void onKeyPress(KeyPressEvent event) { 

      if(stringEntered.length() > textBox.getValue().length()) { 
       // At this point we know that a character has been deleted, 
        so we can clear a list or reset something accordingly 
       ... 
      }