6.10. AbsoluteLayout

AbsoluteLayout allows placing components in arbitrary positions in the layout area. The positions are specified in the addComponent() method with horizontal and vertical coordinates relative to an edge of the layout area. The positions can include a third depth dimension, the z-index, which specifies which components are displayed in front and which behind other components.

The positions are specified by a CSS absolute position string, using the left, right, top, bottom, and z-index properties known from CSS. In the following example, we have a 300 by 150 pixels large layout and position a text field 50 pixels from both the left and the top edge:

// A 400x250 pixels size layout
AbsoluteLayout layout = new AbsoluteLayout();
layout.setWidth("400px");
layout.setHeight("250px");
        
// A component with coordinates for its top-left corner
TextField text = new TextField("Somewhere someplace");
layout.addComponent(text, "left: 50px; top: 50px;");

The left and top specify the distance from the left and top edge, respectively. The right and bottom specify the distances from the right and top edge.

// At the top-left corner
Button button = new Button( "left: 0px; top: 0px;");
layout.addComponent(button, "left: 0px; top: 0px;");

// At the bottom-right corner
Button buttCorner = new Button( "right: 0px; bottom: 0px;");
layout.addComponent(buttCorner, "right: 0px; bottom: 0px;");

// Relative to the bottom-right corner
Button buttBrRelative = new Button( "right: 50px; bottom: 50px;");
layout.addComponent(buttBrRelative, "right: 50px; bottom: 50px;");

// On the bottom, relative to the left side
Button buttBottom = new Button( "left: 50px; bottom: 0px;");
layout.addComponent(buttBottom, "left: 50px; bottom: 0px;");

// On the right side, up from the bottom
Button buttRight = new Button( "right: 0px; bottom: 100px;");
layout.addComponent(buttRight, "right: 0px; bottom: 100px;");

In the above examples, we had components of undefined size and specified the positions of components by a single pair of coordinates. The other possibility is to specify an area and let the component fill the area by specifying a proportinal size for the component, such as "100%". Normally, you use setSizeFull() to take the entire area given by the layout.

// Specify an area that a component should fill
Panel panel = new Panel("A Panel filling an area");
panel.setSizeFull(); // Fill the entire given area
layout.addComponent(panel, "left: 25px; right: 50px; "+
                           "top: 100px; bottom: 50px;");

You can also use proportional coordinates to specify the coordinates:

// A panel that takes 30% to 90% horizontally and
// 20% to 80% vertically
Panel panel = new Panel("A Panel");
panel.setSizeFull(); // Fill the specified area
layout.addComponent(panel, "left: 30%; right: 10%;" +
                           "top: 20%; bottom: 20%;");