java - 设置窗口内部区域的大小

Question

我有一个简单的函数，可以生成包含图像的 JFrame:

 //The window
 JFrame frame = new JFrame();
 //Topmost component of the window
 Container main = frame.getContentPane();
 //Turns out this is probably the simplest way to render image on screen 
 //with guaranteed 1:1 aspect ratio
 JPanel panel = new JPanel() {
    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawImage(image, 0, 0, null);
    }
 };
 //Put the image drawer in the topmost window component
 main.add(panel);
 //Set window size to the image size plus some padding dimensions
 frame.setSize(image.getWidth(null)+1, image.getHeight(null)+15);

 frame.setVisible(true);

结果:

我认为发生这种情况是因为窗口尺寸包括顶部栏和窗口边框的大小。

我还尝试设置 JPanel 的大小并在 JFrame 上调用 pack():

 //Set the size to the panel and let JFrame size itself properly
 panel.setSize(image.getWidth(null), image.getHeight(null));
 frame.pack();

结果更糟:

那么如何精确指定内部窗口尺寸(以像素为单位)？

Here's the full function code.

Answer 1

通过重写 JPanel 的 getPreferredSize 方法并在 JFrame< 上调用 pack() 来指定面板的首选大小 使其可见之前

JPanel panel = new JPanel() {
    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawImage(image, 0, 0, null);
    }
    @Override
    public Dimension getPreferredSize(){
        return new Dimension(image.getWidth(), image.getHeight());
    }
};

请参阅 Use of overriding getPreferredSize() instead of using setPreferredSize() for fixed size Components 中的答案关于此技术或 setPreferredSize 方法的使用和效果