GridLayout行为不端

Question

我正在尝试用手写Swing（是的，我知道），由于某种原因，我在这里创建了这个部分小组：

private JPanel createColorSliderPanel() {
    JPanel colorSliderPanel = new JPanel(new GridLayout(3, 1, 0, 5));

    JPanel redSliderPanel = new JPanel(new BorderLayout());
    JPanel greenSliderPanel = new JPanel(new BorderLayout());
    JPanel blueSliderPanel = new JPanel(new BorderLayout());

    GridLayout grid = (GridLayout) colorSliderPanel.getLayout();


    redSlider = new JSlider();
    greenSlider = new JSlider();
    blueSlider = new JSlider();

    redField = new JTextField();
    greenField = new JTextField();
    blueField = new JTextField();

    redField.setEditable(false);
    greenField.setEditable(false);
    blueField.setEditable(false);

    JLabel redLabel = new JLabel("Red");
    JLabel greenLabel = new JLabel("Green");
    JLabel blueLabel = new JLabel("Blue");

    redLabel.setPreferredSize(new Dimension(64, 16));
    redField.setPreferredSize(new Dimension(32, 16));
    redSliderPanel.add(redLabel, BorderLayout.WEST);
    redSliderPanel.add(redSlider, BorderLayout.CENTER);
    redSliderPanel.add(redField, BorderLayout.EAST);

    greenLabel.setPreferredSize(new Dimension(64, 16));
    greenField.setPreferredSize(new Dimension(32, 16));
    greenSliderPanel.add(redLabel, BorderLayout.WEST);
    greenSliderPanel.add(redSlider, BorderLayout.CENTER);
    greenSliderPanel.add(redField, BorderLayout.EAST);

    blueLabel.setPreferredSize(new Dimension(64, 16));
    blueField.setPreferredSize(new Dimension(32, 16));
    blueSliderPanel.add(redLabel, BorderLayout.WEST);
    blueSliderPanel.add(redSlider, BorderLayout.CENTER);
    blueSliderPanel.add(redField, BorderLayout.EAST);


    colorSliderPanel.add(redSliderPanel);
    colorSliderPanel.add(greenSliderPanel);
    colorSliderPanel.add(blueSliderPanel);

    return colorSliderPanel;
}

无效：

它应该将我制作的三个面板叠加在一起。我把它添加到我的JFrame中：

JPanel sliderPanel = createColorSliderPanel();
...
contentPane.add(sliderPanel, BorderLayout.SOUTH);

有什么理由不能正常显示？

Answer 1

问题是，您只需将redSlider/Field/Label添加到所有其他面板

redSliderPanel.add(redLabel, BorderLayout.WEST);
redSliderPanel.add(redSlider, BorderLayout.CENTER);
redSliderPanel.add(redField, BorderLayout.EAST);

greenSliderPanel.add(redLabel, BorderLayout.WEST);
greenSliderPanel.add(redSlider, BorderLayout.CENTER);
greenSliderPanel.add(redField, BorderLayout.EAST);

blueSliderPanel.add(redLabel, BorderLayout.WEST);
blueSliderPanel.add(redSlider, BorderLayout.CENTER);
blueSliderPanel.add(redField, BorderLayout.EAST);

执行此操作后，系统会从之前添加的容器中移除redSlider，redField和redLabel，这意味着它只会显示在blueSliderPanel上。

不要使用setPreferred/Minimum/MaximumSize，您不能控制组件衡量其所需大小的指标。为组件提供调整提示，以便他们做出更好的决策。

redField = new JTextField(4);
greenField = new JTextField(4);
blueField = new JTextField(4);

  

然后不要先将字段添加到子面板

然后不要先将字段添加到单独的面板中，但是，您可能会发现类似GridBagLayout的内容是更好的选择......

JPanel colorSliderPanel = new JPanel(new GridBagLayout());

redSlider = new JSlider();
greenSlider = new JSlider();
blueSlider = new JSlider();

redField = new JTextField(4);
greenField = new JTextField(4);
blueField = new JTextField(4);

redField.setEditable(false);
greenField.setEditable(false);
blueField.setEditable(false);

JLabel redLabel = new JLabel("Red");
JLabel greenLabel = new JLabel("Green");
JLabel blueLabel = new JLabel("Blue");

addTo(colorSliderPanel, redLabel, redSlider, redField, 0);
addTo(colorSliderPanel, greenLabel, greenSlider, greenField, 1);
addTo(colorSliderPanel, blueLabel, blueSlider, blueField, 2);

addTo方法......

protected void addTo(JPanel parent, JLabel label, JSlider slider, JTextField field, int gridY) {

    GridBagConstraints gbc = new GridBagConstraints();
    gbc.anchor = GridBagConstraints.WEST;
    gbc.gridx = 0;
    gbc.gridy = gridY;
    parent.add(label, gbc);

    gbc.fill = GridBagConstraints.HORIZONTAL;
    gbc.gridx++;
    gbc.weightx = 1;
    parent.add(slider, gbc);

    gbc.gridx++;
    gbc.weightx = 0;
    parent.add(field, gbc);

}