在调用 add() 之前设置约束两次

Question

我正在使用来自 Oracle 的教程在 swing 中学习 GridBagLayout。
众所周知，我们可以在被1 component.Here使用后重新设置约束我注意到作者在调用方法add()之前再次设置了约束。

public class GridBagLayoutDemo {
//Here I have no idea why these 3 lines for
    final static boolean shouldFill = true;
    final static boolean shouldWeightX = true;
    final static boolean RIGHT_TO_LEFT = false;

    public static void addComponentsToPane(Container pane) {
//1)why not just ignore the above declaration and just type 
//pane.setComponentOrientation(ComponentOrientation.RIGHT_TO_LEFT); ?

        if (RIGHT_TO_LEFT) {
            pane.setComponentOrientation(ComponentOrientation.RIGHT_TO_LEFT);
        }

        JButton button;
    pane.setLayout(new GridBagLayout());
    GridBagConstraints c = new GridBagConstraints();
//same go to here
    if (shouldFill) {
    //natural height, maximum width
    c.fill = GridBagConstraints.HORIZONTAL;
    }
//2)the author set the constraint in above line,then author set it again in below line
    button = new JButton("Button 1");
    if (shouldWeightX) {
    c.weightx = 0.5;
    }
//here it is
    c.fill = GridBagConstraints.HORIZONTAL;
    c.gridx = 0;
    c.gridy = 0;
    pane.add(button, c);

谁能回答我的两个问题？

Answer 1

我认为第二个布局方向：c.fill = GridBagConstraints.HORIZONTAL;是一个错误，第一个是有条件的，取决于之前设置的值"shouldFill"。所以我不同意这个变量什么都不做。

在调用 add() 之前设置约束两次

Setting the constraint twice before calling add()

java

swing

gridlayoutmanager