The GridBagLayout is a flexible layout manager, but is also notoriously difficult to use. Some of the most common and difficult to debug problems occur when the amount of space allocated to components is not what was expected and/or the components are not positioned where expected within the available space. In fact, these two separate problems often occur at the same time, which increases the complexity of debugging them. Fortunately, there’s a simple step you can take which will provide you with valuable feedback on the behavior of the layout manager.
When experiencing problems with the GridBagLayout, it’s often helpful to set the background color of a component that appears to be incorrectly sized and/or positioned, along with any components that are adjacent to it. If you do, it’s best to use colors that provide a clear contrast to the “normal” display colors (for example, use bright colors like red, blue, and green when the display is mostly light gray). For example:
Label label1 = new Label("This is a test");label1.setBackground(Color.red);add(label1);...Label label2 = new Label("This is another test");label2.setBackground(Color.blue);add(label2);
This code will set the background color of one label to red and the other to blue, which will make them stand out from the background and from each other. Having this visual information on the size and position of components in question can make it much easier to find problems in your GridBagLayout code.