Eclipse建议使用Null Pointer异常，但我相信我初始化了我的对象 [英] Eclipse suggests Null Pointer exception, though I believe I initialized my object

问题描述

标题说我有NPE错误。它发生在一行：

  while（getWidth（）> bowl.getX（）+ 10）{
  

如果我删除它，它显示它发生在下一行：

  bowl.move（10.0，0）; 
  

我得出结论，eclipse没有看到我的碗初始化。
为什么？ 新GOVE不是处理吗？
我在这里的一个线程中看到，一个解决方案是将声明和初始化分解为不同的行，但我认为这不太可能是一个主要的解决方案（此外，它在我的情况下没有帮助）关于这段代码的任何建议？

此代码应该创建一个圆圈，将其放在屏幕的左上角，然后按鼠标左键移动圆圈被点击。圈子成功绘制，点击后会显示NPE讯息。

  import acm.program。*; 
 import acm.graphics。*; 
 import java.awt.event。*; 
 
 public class animation extends GraphicsProgram {
 
 public void init（）{
 GOval bowl = new GOval（10,10）; 
加（碗）; 
 addMouseListeners（）; 
} 
 
 
 public void mouseClicked（MouseEvent e）{
 while（getWidth（）> bowl.getX（）+ 10）{
碗.move（10.0，0）; 
 pause（50）; 
} 
} 
 
私人GOval碗; 
} 
  

解决方案

行：

  GOval bowl = new GOval（10,10）; 
  

正在声明一个新的GOval并隐藏底部定义的全局GOval。

该行应该是：

  bowl = new GOval（10,10）; 
  

As the title says I have NPE error. It happens on line:

while (getWidth() > bowl.getX()+10) {

If I remove it, it shows it happens on next line:

bowl.move(10.0, 0);

I concluded that eclipse does not see my "bowl" initialized. Why? Doesn't "new GOval" deal with that? I've seen in one of the threads here that a solution was to split declaration and initialization to different lines, but I think it is unlikely to be a primary solution (besides, it didn't help in my case) Any suggestions on this code?

This code is supposed to create a circle, put it in the left-upper corner of the screen, and move the circle after mouse-button is clicked. The circle is drawn successfully, but the NPE message shows up after the click.

import acm.program.*;
import acm.graphics.*;
import java.awt.event.*;

public class animation extends GraphicsProgram {

public void init() {
    GOval bowl = new GOval(10,10);
    add(bowl);
    addMouseListeners();
}


public void mouseClicked(MouseEvent e) {
        while (getWidth() > bowl.getX()+10) {
        bowl.move(10.0, 0);
        pause(50);
    }
}

private GOval bowl; 
}

解决方案

The line:

GOval bowl = new GOval(10,10);

is declaring a new GOval and hiding the global GOval defined at the bottom.

That line should just be:

bowl = new GOval(10,10);

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