摇摆：GridBagLayouts锚不能嵌套在另一个GridBagLayout中

Question

I am setting a first GridBagLayout to a main JPanel . To this Panel, ten other panels were added with this layout (outerConstraints). The sub-panels contains an amount of texts, which should be placed WEST with a new Layout and innerConstraints . But they center.

After testing a little bit, i found out that the texts / images ARE placed WEST, but only, if the outerConstraints do not fill the white panel horizontally. The problem is, that i can not remove this command, because i need every panel to have the same width.

Is there a possiblity to allow outerConstraints to fill up AND to make its nested GridBagLayout positioning the text left?

setLayout(new GridBagLayout());

GridBagConstraints outerConstraints = new GridBagConstraints();
outerConstraints.insets = new Insets(5, 5, 5, 5);
outerConstraints.fill = GridBagConstraints.HORIZONTAL;    // seems to be reason, but needed.

    for (int i = 0; i < 10; i++) {

        outerConstraints.gridx = i % 2;
        outerConstraints.gridy = i / 2;

        JPanel agentVisitCard = new JPanel();
        add(agentVisitCard, outerConstraints);

        GridBagConstraints innerConstraints = new GridBagConstraints();
        innerConstraints.anchor = GridBagConstraints.WEST;                 //fails
        innerConstraints.insets = new Insets(5, 5, 5, 5);

        GridBagLayout layout = new GridBagLayout();
        agentVisitCard.setLayout(layout);

        (...)

        JLabel label = new JLabel("Agent " + (i + 1) + ":");

        innerConstraints.gridx = 0;
        innerConstraints.gridy = 0;

        agentVisitCard.add(label, innerConstraints);

Agent 3 does not align left:

Answer 1

The reason the anchor wasn't working is because the components had no weight. Without that, the area given to the component is only the minimum size needed, ie the size of the component itself, and no bigger.

Here is a quote from the swing tutorials (under the weightx, weighty section) that explains it:

Unless you specify at least one non-zero value for weightx or weighty, all the components clump together in the center of their container. This is because when the weight is 0.0 (the default), the GridBagLayout puts any extra space between its grid of cells and the edges of the container.

By default, the weightx and weighty are 0, which is why it was not working for you. Since you only wanted to anchor it horizontally, setting the weightx to a non-zero value allowed that to work. If you wanted a vertical anchor, you would need to set the weighty as well.

An explanation of how the weightx and weighty values should be used follows that:

Generally weights are specified with 0.0 and 1.0 as the extremes: the numbers in between are used as necessary. Larger numbers indicate that the component's row or column should get more space.

Although they recommend using values between 0.0 and 1.0, it is not necessary. Any double value will work. What's important is the ratio between the weights of components if you have several of them.