代码适用于java图形，但不适用于graphics2d

发布于 2024-07-13 14:56:02 字数 252 浏览 9 评论 0原文

在 Paint 组件内。它以g为参数，g可以是graphics或graphics2d。该类扩展了 jpanel。那么：

super.paintComponent(g);
this.setBackground( Color.BLACK );

如果 g 是graphics，它可以工作，但如果它是graphics2d，它就不行。它可以同时编译两者，但graphics2d不会改变背景颜色。怎么会？

原文

inside a paintcomponent. it takes g as parameter, and g can be graphics or graphics2d. the class extends jpanel. then:

super.paintComponent(g);
this.setBackground( Color.BLACK );

if g is graphics it works, but if it's graphics2d it doesn't. it compiles with both, but graphics2d doesn't change the background color. how come?

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痴情 2024-07-20 14:56:02

JPanel （它是 JComponent）只有一个 paintComponent(Graphics) 方法。它没有带有签名 paintComponent(Graphics2D) 的方法。

重写 paintComponent(Graphics) 方法可以通过以下方式完成：

public void paintComponent(Graphics g)
{
    // Do things.
}

但是，像下面这样使用 paintComponent(Graphics2D) 签名定义一个方法是合法的，但是它永远不会被调用，因为它不会覆盖 JComponent 中定义的任何方法：

public void paintComponent(Graphics2D g)
{
    // Do things.
    // However, this method will never be called, as it is not overriding any
    // method of JComponent, but is a method of the class this is defined in.
}

JComponent 类（它是 JPanel 的超类）的 Java API 规范）有一个方法摘要，其中列出了属于该类的所有方法。

有关 Swing 中绘画的更多信息；

JPanel (which is a subclass of JComponent) only has a paintComponent(Graphics) method. It does not have a method with the signature paintComponent(Graphics2D).

Overriding the paintComponent(Graphics) method can be accomplished by the following:

public void paintComponent(Graphics g)
{
    // Do things.
}

However, defining a method with the signature with paintComponent(Graphics2D) like the following is legal, but it won't ever be called, as it is not overriding any method that is defined in JComponent:

public void paintComponent(Graphics2D g)
{
    // Do things.
    // However, this method will never be called, as it is not overriding any
    // method of JComponent, but is a method of the class this is defined in.
}

The Java API specifications for the JComponent class (which is the superclass of JPanel) has a method summary which lists all the methods that are part of the class.

More information about painting in Swing;

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