java swing-如何更改窗口背景 [英] java swing - how to change window background

问题描述

我试图创建一个将窗口背景从默认切换为红色的按钮. 我没有找到任何与默认颜色匹配的预设颜色，因此在创建它时尝试从panel.getBackground中获取它. line 11出现错误，我不知道如何检查当前背景色.

I was trying to make a button that switches the window background from default to red. I haven't found any preset colors to match the default so i tried to get it from panel.getBackground when i created it. I have an error at line 11, i don't know how to check the current background color.

JPanel panel = new JPanel();
    panel.setBounds(0, 0, 434, 262);
    frame.getContentPane().add(panel);
    panel.setLayout(null);
    panel.setVisible(true);
    Color c=panel.getBackground();

    JButton btnRed = new JButton("Red");
    btnRed.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            if(panel.getBackground(c));{
                panel.setBackground(Color.RED);
            }
            else{
                panel.setBackground(c);
            }
        }
    });

推荐答案

您想比较Color，这是一个Object，所以equals()是这样. c6>，并在找到;后完成，因此:

You want to compare the Color, this is an Object so equals() is the way... also an if expects a boolean and will finish when ; is found, so this:

if(panel.getBackground(c));{
// ↑ not a boolean        ↑
//                        ↑
//                        ; is wrong

必须

if(panel.getBackground().equals(c)){

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