java - 请帮助我使用 Java 中的 JFrame 和 BorderLayout

Question

有人可以告诉我为什么我的 JList 和 JLabel 没有自动调整大小以填满整个屏幕吗？另外为什么 JButton 不自动调整大小？非常感谢

public class testing extends JFrame {

    private String[] testArray = {"apple", "banana", "cat"};
    private JPanel firstLayer = new JPanel();
    private JPanel secondLayerLeft = new JPanel();
    private JPanel secondLayerRight = new JPanel();
    private JList<String> leftText = new JList<String>();
    private JLabel rightOutput = new JLabel();
    private JButton button = new JButton("test button");

    public testing(){
        firstLayer.setLayout(new BorderLayout());
        firstLayer.add(secondLayerLeft, BorderLayout.WEST);
        firstLayer.add(secondLayerRight, BorderLayout.EAST);
        firstLayer.add(button, BorderLayout.SOUTH);

        secondLayerLeft.add(leftText);
        leftText.setListData(testArray);
        secondLayerRight.add(rightOutput);
        rightOutput.setText("testing 12345");


        secondLayerLeft.setBorder(new EtchedBorder());
        secondLayerRight.setBorder(new EtchedBorder());

        this.add(firstLayer);
    }


    public static void main(String[] args) {
        testing gui = new testing();
        gui.setSize(700, 800);
        gui.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        gui.setVisible(true);
    }

}

Answer 1

这是BorderLayout的基本功能。只有 CENTER 位置会自动调整大小。任何边框组件可以更改大小的唯一方法是，它们实际上更改大小(getPreferredSize 在执行下一个布局之前更改)