TypeError：錯誤＃2007：參數子項必須爲非空值。在flash.display :: DisplayObjectContainer/addChild（）

Question

創建一個按鈕，現在試圖將其添加到屏幕上，我得到這個錯誤。按鈕的代碼 -

private function submitButton():void { 
    submit_button=new SimpleButton(); 
    submit_button.x=200; 
    submit_button.y=200; 
    submit_button.upState=buttonShape(); 
    submit_button.overState=buttonShape(); 
    submit_button.downState=buttonShape(); 
} 

private function buttonShape() { 
    var rectangle:Shape = new Shape; // initializing the variable named rectangle 
    rectangle.graphics.beginFill(0x8C2B44); // choosing the colour for the fill, here it is red 
    rectangle.graphics.drawRect(200, 200, 300,20); // (x spacing, y spacing, width, height) 
    rectangle.graphics.endFill(); 
} 

我已經聲明它作爲一個公共變種，我使用addChild(submit_button);

• 編輯 - 所有的代碼是在一個類文件。我在開始時設置了提交按鈕， - private var submit_button：SimpleButton;我有一個函數的私人功能submitButton（）：void { submit_button = new SimpleButton（）; submit_button.x = 200; submit_button.y = 200;

  submit_button.upState=buttonShape(); 
      submit_button.overState=buttonShape(); 
      submit_button.downState=buttonShape(); 
  
  } and the drawing function seen above. and i add it to the stage in another function - private function gameOver():void { 
  
      addChild(submit_button); 
      addChild(gameOver1);  basically this function is called on a hit test. and i have a text box that appears (this works) but when i add the button i get the error 
  

Answer 1

功能buttonShape()不返回任何東西。您的inital行var rectangle:Shape = new Shape;正在創建一個局部變量，該變量超出了範圍，並在函數結束時不再存在。

由於buttonShape()不返回任何東西，它的實際功能的簽名是：

private function buttShape():void {} 

與return void;在函數結束被暗示。

這意味着你的代碼

submit_button.upState=buttonShape(); 

基本上編譯爲：你在哪裏使用addChild（submit_button）

submit_button.upState=null;