Java

Types

For a visual representation and more info see: A Visual Guide to Layout Managers Several AWT and Swing classes provide layout managers for general use:

• BorderLayout: default layout for content panes. Places components in up to five areas: top, bottom, left, right, and center. All extra space is placed in the center area. Tool bars that are created using JToolBar must be created within a BorderLayout container, if you want to be able to drag and drop the bars away from their starting positions;
• BoxLayout: puts components in a single row or column;
• CardLayout: lets you implement an area that contains different components at different times. An alternative to using CardLayout is using a tabbed pane component;
• FlowLayout: default layout manager for every JPanel. It simply lays out components in a single row, starting a new row if its container is not sufficiently wide;
• GridBagLayout: if you are not using a GUI builder (GridLayout) but want to manually build your GUI then this is recommended as the next most flexible and powerful layout manager - It aligns components by placing them within a grid of cells, allowing components to span more than one cell. The rows in the grid can have different heights, and grid columns can have different widths;
• GridLayout: 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;
• GroupLayout: can be used manually but it was developed to be used by GUI builder tools (ex. NetBeans IDE GUI builder uses this layout by default). This layout works by defining group of components that related to each other (ex. align components together). The GUI builder will give you visual clues when you drag and drop the components next to each-other informing you how the elements will be grouped. For examples of this visual clues check this GroupLayout Example.
• SpringLayout: a flexible layout manager designed for use by GUI builders;

Using Layout Managers

Set

As a rule, the only containers whose layout managers you need to worry about are:

• JPanels (default is FlowLayout)

  JPanel panel = new JPanel(new BorderLayout());

• content panes (default is BorderLayout)
  After a container has been created, you can set its layout manager using the setLayout method. For example:

  Container contentPane = frame.getContentPane();
  contentPane.setLayout(new FlowLayout());

Note: unless you are using JToolBar, the FlowLayout and BorderLayout managers are only useful for prototyping.

---

Add components

Depends on the Layout Manager you are using.

The how-to section for each layout manager has details on what, if any, arguments you need to specify to the add method. Some layout managers, such as GridBagLayout and SpringLayout, require elaborate setup procedures. Many layout managers, however, simply place components based on the order they were added to their container.
Example:

pane.add(aComponent, BorderLayout.PAGE_START);

NOTE: Swing containers other than JPanel and content panes generally provide API that you should use instead of the add method. For example, instead of adding a component directly to a scroll pane (or, actually, to its viewport), you either specify the component in the JScrollPane constructor or use setViewportView.

---

Set Size and Alignment hints

Sometimes you need to customize the size hints that a component provides to its container's layout manager, so that the component will be laid out well.
You can invoke the component's methods for:

• setting size hints: setMinimumSize, setPreferredSize, and setMaximumSize;
• setting alignment hints (for example, you can specify that the top edges of two components should be aligned): setAlignmentX and setAlignmentY methods;

NOTE: Many layout managers do not pay attention to a component's requested maximum size. However, BoxLayout and SpringLayout do. Furthermore, GroupLayout provides the ability to set the minimum, preferred or maximum size explicitly, without touching the component (How to Use BoxLayout).

---

Tips on Choosing a Layout Manager

Check the tips at the bottom of the page: Using Layout Managers

How Layout Managers work

Layout managers basically do two things: Calculate the minimum/preferred/maximum sizes for a container and lay out the container's children.

Some methods: 

• Container.validate: used to validate an invalid container (isValid() returns true). For a container to be valid, all the container's children must be laid out already and must all be valid also. 
• Window.pack: validates the window and lays out the window's component hierarchy for the first time. After a component is created it is in the invalid state by default. 
• revalidate and repaint methods: If the size of a component changes, for example following a change of font, the component must be resized and repainted by calling the revalidate and repaint methods on that component. Both revalidate and repaint are thread-safe — you need not invoke them from the event-dispatching thread.

---

Code samples on how to use different Layout Managers Types

check this page

JPanel pane = new JPanel();
pane.setBorder(BorderFactory.createLineBorder(Color.black));

Components

---

---

Detecting mouse double click

someComponent.addMouseListener(new MouseAdapter(){
 public void mouseClicked(MouseEvent event){
  if (e.getClickCount() == 2 && !e.isConsumed()) {
   e.consume();
   //handle double click. 
  } 
 }
}

ref: How to detect double-click mouse events in Swing