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Showing content from https://docs.oracle.com/en/java/javase/19/docs/api/java.desktop/java/awt/GridBagLayout.html below:

GridBagLayout (Java SE 19 & JDK 19)

All Implemented Interfaces:
LayoutManager, LayoutManager2, Serializable

The

GridBagLayout

class is a flexible layout manager that aligns components vertically, horizontally or along their baseline without requiring that the components be of the same size. Each

GridBagLayout

object maintains a dynamic, rectangular grid of cells, with each component occupying one or more cells, called its

display area

.

Each component managed by a GridBagLayout is associated with an instance of GridBagConstraints. The constraints object specifies where a component's display area should be located on the grid and how the component should be positioned within its display area. In addition to its constraints object, the GridBagLayout also considers each component's minimum and preferred sizes in order to determine a component's size.

The overall orientation of the grid depends on the container's ComponentOrientation property. For horizontal left-to-right orientations, grid coordinate (0,0) is in the upper left corner of the container with x increasing to the right and y increasing downward. For horizontal right-to-left orientations, grid coordinate (0,0) is in the upper right corner of the container with x increasing to the left and y increasing downward.

To use a grid bag layout effectively, you must customize one or more of the GridBagConstraints objects that are associated with its components. You customize a GridBagConstraints object by setting one or more of its instance variables:

GridBagConstraints.gridx, GridBagConstraints.gridy
Specifies the cell containing the leading corner of the component's display area, where the cell at the origin of the grid has address gridx = 0, gridy = 0. For horizontal left-to-right layout, a component's leading corner is its upper left. For horizontal right-to-left layout, a component's leading corner is its upper right. Use GridBagConstraints.RELATIVE (the default value) to specify that the component be placed immediately following (along the x axis for gridx or the y axis for gridy) the component that was added to the container just before this component was added.
GridBagConstraints.gridwidth, GridBagConstraints.gridheight
Specifies the number of cells in a row (for gridwidth) or column (for gridheight) in the component's display area. The default value is 1. Use GridBagConstraints.REMAINDER to specify that the component's display area will be from gridx to the last cell in the row (for gridwidth) or from gridy to the last cell in the column (for gridheight). Use GridBagConstraints.RELATIVE to specify that the component's display area will be from gridx to the next to the last cell in its row (for gridwidth) or from gridy to the next to the last cell in its column (for gridheight).
GridBagConstraints.fill
Used when the component's display area is larger than the component's requested size to determine whether (and how) to resize the component. Possible values are GridBagConstraints.NONE (the default), GridBagConstraints.HORIZONTAL (make the component wide enough to fill its display area horizontally, but don't change its height), GridBagConstraints.VERTICAL (make the component tall enough to fill its display area vertically, but don't change its width), and GridBagConstraints.BOTH (make the component fill its display area entirely).
GridBagConstraints.ipadx, GridBagConstraints.ipady
Specifies the component's internal padding within the layout, how much to add to the minimum size of the component. The width of the component will be at least its minimum width plus ipadx pixels. Similarly, the height of the component will be at least the minimum height plus ipady pixels.
GridBagConstraints.insets
Specifies the component's external padding, the minimum amount of space between the component and the edges of its display area.
GridBagConstraints.anchor
Specifies where the component should be positioned in its display area. There are three kinds of possible values: absolute, orientation-relative, and baseline-relative. Orientation relative values are interpreted relative to the container's ComponentOrientation property while absolute values are not. Baseline relative values are calculated relative to the baseline. Valid values are:
GridBagConstraints.weightx, GridBagConstraints.weighty
Used to determine how to distribute space, which is important for specifying resizing behavior. Unless you specify a weight for at least one component in a row (weightx) and column (weighty), all the components clump together in the center of their container. This is because when the weight is zero (the default), the GridBagLayout object puts any extra space between its grid of cells and the edges of the container.

Each row may have a baseline; the baseline is determined by the components in that row that have a valid baseline and are aligned along the baseline (the component's anchor value is one of BASELINE, BASELINE_LEADING or BASELINE_TRAILING). If none of the components in the row has a valid baseline, the row does not have a baseline.

If a component spans rows it is aligned either to the baseline of the start row (if the baseline-resize behavior is CONSTANT_ASCENT) or the end row (if the baseline-resize behavior is CONSTANT_DESCENT). The row that the component is aligned to is called the prevailing row.

The following figure shows a baseline layout and includes a component that spans rows:

This layout consists of three components:

Because the second button and the panel share the same prevailing row, they are both aligned along their baseline.

Components positioned using one of the baseline-relative values resize differently than when positioned using an absolute or orientation-relative value. How components change is dictated by how the baseline of the prevailing row changes. The baseline is anchored to the bottom of the display area if any components with the same prevailing row have a baseline-resize behavior of CONSTANT_DESCENT, otherwise the baseline is anchored to the top of the display area. The following rules dictate the resize behavior:

If you position a component along the baseline, but the component does not have a valid baseline, it will be vertically centered in its space. Similarly if you have positioned a component relative to the baseline and none of the components in the row have a valid baseline the component is vertically centered.

The following figures show ten components (all buttons) managed by a grid bag layout. Figure 2 shows the layout for a horizontal, left-to-right container and Figure 3 shows the layout for a horizontal, right-to-left container.

Figure 2: Horizontal, Left-to-Right

Figure 3: Horizontal, Right-to-Left


Each of the ten components has the fill field of its associated GridBagConstraints object set to GridBagConstraints.BOTH. In addition, the components have the following non-default constraints:

Here is the code that implements the example shown above:

 import java.awt.*;
 import java.util.*;
 import java.applet.Applet;

 public class GridBagEx1 extends Applet {

     protected void makebutton(String name,
                               GridBagLayout gridbag,
                               GridBagConstraints c) {
         Button button = new Button(name);
         gridbag.setConstraints(button, c);
         add(button);
     }

     public void init() {
         GridBagLayout gridbag = new GridBagLayout();
         GridBagConstraints c = new GridBagConstraints();

         setFont(new Font("SansSerif", Font.PLAIN, 14));
         setLayout(gridbag);

         c.fill = GridBagConstraints.BOTH;
         c.weightx = 1.0;
         makebutton("Button1", gridbag, c);
         makebutton("Button2", gridbag, c);
         makebutton("Button3", gridbag, c);

         c.gridwidth = GridBagConstraints.REMAINDER; //end row
         makebutton("Button4", gridbag, c);

         c.weightx = 0.0;                //reset to the default
         makebutton("Button5", gridbag, c); //another row

         c.gridwidth = GridBagConstraints.RELATIVE; //next-to-last in row
         makebutton("Button6", gridbag, c);

         c.gridwidth = GridBagConstraints.REMAINDER; //end row
         makebutton("Button7", gridbag, c);

         c.gridwidth = 1;                //reset to the default
         c.gridheight = 2;
         c.weighty = 1.0;
         makebutton("Button8", gridbag, c);

         c.weighty = 0.0;                //reset to the default
         c.gridwidth = GridBagConstraints.REMAINDER; //end row
         c.gridheight = 1;               //reset to the default
         makebutton("Button9", gridbag, c);
         makebutton("Button10", gridbag, c);

         setSize(300, 100);
     }

     public static void main(String args[]) {
         Frame f = new Frame("GridBag Layout Example");
         GridBagEx1 ex1 = new GridBagEx1();

         ex1.init();

         f.add("Center", ex1);
         f.pack();
         f.setSize(f.getPreferredSize());
         f.show();
     }
 }
Since:
1.0
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