Trail: Creating a GUI With JFC/Swing
Lesson: Laying Out Components Within a Container

如何使用 GridLayout

注意: This lesson covers writing layout code by hand, which can be challenging. If you are not interested in learning all the details of layout management, you might prefer to use the GroupLayout layout manager combined with a builder tool to lay out your GUI. One such builder tool is the NetBeans IDE. Otherwise, if you want to code by hand and do not want to use GroupLayout, then GridBagLayout is recommended as the next most flexible and powerful layout manager.

If you are interested in using JavaFX to create your GUI, see Working With Layouts in JavaFX.

The following figure represents a snapshot of an application that uses the GridLayout class.

Click the Launch button to run GridLayoutDemo using Java™ Web Start (download JDK 7 or later). Alternatively, to compile and run the example yourself, consult the example index.

The complete code of this demo is in the GridLayoutDemo.java file.

A GridLayout object places components in a grid of cells. Each component takes all the available space within its cell, and each cell is exactly the same size. If the GridLayoutDemo window is resized, the GridLayout object changes the cell size so that the cells are as large as possible, given the space available to the container.

The code snippet below creates the GridLayout object and the components it manages.


GridLayout experimentLayout = new GridLayout(0,2);

...

        compsToExperiment.setLayout(experimentLayout);

        compsToExperiment.add(new JButton("Button 1"));
        compsToExperiment.add(new JButton("Button 2"));
        compsToExperiment.add(new JButton("Button 3"));
        compsToExperiment.add(new JButton("Long-Named Button 4"));
        compsToExperiment.add(new JButton("5"));

The constructor of the GridLayout class creates an instance that has two columns and as many rows as necessary.

Use combo boxes to set up how much vertical or horizontal padding is put around the components. Then click the Apply gaps button. The following code snippet shows how your selection is processed by using the setVgap and setHgap methods of the GridLayout class:


applyButton.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent e){
                //Get the horizontal gap value
                String horGap = (String)horGapComboBox.getSelectedItem();
                //Get the vertical gap value
                String verGap = (String)verGapComboBox.getSelectedItem();
                //Set up the horizontal gap value
                experimentLayout.setHgap(Integer.parseInt(horGap));
                //Set up the vertical gap value
                experimentLayout.setVgap(Integer.parseInt(verGap));
                //Set up the layout of the buttons
                experimentLayout.layoutContainer(compsToExperiment);
            }
        });

The GridLayout API

The following table lists constructors of the GridLayout class that specify the number of rows and columns.

The `GridLayout` class constructors
构造函数	目的
`GridLayout(int rows, int cols)`	Creates a grid layout with the specified number of rows and columns. All components in the layout are given equal size. One, but not both, of `rows` and `cols` can be zero, which means that any number of objects can be placed in a row or in a column.
`GridLayout(int rows, int cols, int hgap, int vgap)`	Creates a grid layout with the specified number of rows and columns. In addition, the horizontal and vertical gaps are set to the specified values. Horizontal gaps are places between each of columns. Vertical gaps are placed between each of the rows.

The GridLayout class has two constructors:

Examples that Use GridLayout

The following table lists code examples that use the GridLayout class and provides links to related sections.

例子	Where Described	Notes
`GridLayoutDemo`	This page	Uses a 2-column grid.
`ComboBoxDemo2`	如何使用组合框	One of many examples that use a 1x1 grid to make a component as large as possible.
`LabelDemo`	如何使用标签	Uses a 3-row grid.