6.3. VerticalLayout and HorizontalLayout

VerticalLayout vertical = new VerticalLayout ();
vertical.addComponent(new TextField("Name"));
vertical.addComponent(new TextField("Street address"));
vertical.addComponent(new TextField("Postal code"));
main.addComponent(vertical);

The components contained within an ordered layout can be laid out in a number of different ways depending on how you specify their height or width in the primary direction of the layout component.

Figure 6.1, “Component Widths in HorizontalLayout” above gives a summary of the sizing options for a HorizontalLayout. Let us break down the figure as follows.

If a VerticalLayout has undefined height or HorizontalLayout undefined width, the layout will shrink to fit the contained components so that there is no extra space between them.

HorizontalLayout fittingLayout = new HorizontalLayout();
fittingLayout.setWidth(Sizeable.SIZE_UNDEFINED, 0);
fittingLayout.addComponent(new Button("Small"));
fittingLayout.addComponent(new Button("Medium-sized"));
fittingLayout.addComponent(new Button("Quite a big component"));
parentLayout.addComponent(fittingLayout);

If such a vertical layout continues below the bottom of a window (a Window object), the window will pop up a vertical scroll bar on the right side of the window area. This way, you get a "web page".

If you set a HorizontalLayout to a defined size horizontally or a VerticalLayout vertically, and there is space left over from the contained components, the extra space is distributed equally between the component cells. The components are aligned within these cells according to their alignment setting, top left by default, as in the example below.

fixedLayout.setWidth("400px");

Using percentual sizes for components contained in a layout requires answering the question, "Percentage of what?" There is no sensible default answer for this question in the current implementation of the layouts, so in practice, you may not define "100%" size alone.

Often, you want to have one component that takes all the available space left over from other components. You need to set its size as 100% and set it as expanding with setExpandRatio(). The second parameter for the method is an expansion ratio, which is relevant if there are more than one expanding component, but its value is irrelevant for a single expanding component.

HorizontalLayout layout = new HorizontalLayout();
layout.setWidth("400px");

// These buttons take the minimum size.
layout.addComponent(new Button("Small"));
layout.addComponent(new Button("Medium-sized"));

// This button will expand.
Button expandButton = new Button("Expanding component");

// Use 100% of the expansion cell's width.
expandButton.setWidth("100%");

// The component must be added to layout before setting the ratio.
layout.addComponent(expandButton);

// Set the component's cell to expand.
layout.setExpandRatio(expandButton, 1.0f);

parentLayout.addComponent(layout);

Notice that you must call setExpandRatio() after addComponent(), because the layout can not operate on an component that it doesn't (yet) include.

Warning: A layout that contains components with percentual size must have a defined size! If a layout has undefined size and component has, say, 100% size, the component would fill the space given by the layout, while the layout would shrink to fit the space taken by the component, which is a paradox. This requirement holds for height and width separately. The debug mode allows detecting such invalid cases; see Section 10.3.1, “Debug Mode”.

If you specify an expand ratio for multiple components, they will all try to use the available space according to the ratio.

HorizontalLayout layout = new HorizontalLayout();
                layout.setWidth("400px");

// Create three equally expanding components.
String[] captions = { "Small", "Medium-sized", "Quite a big component" };
for (int i = 1; i <= 3; i++) {
    Button button = new Button(captions[i-1]);
    button.setWidth("100%");
    layout.addComponent(button);

    // Have uniform 1:1:1 expand ratio.
    layout.setExpandRatio(button, 1.0f);
}

As we used the same ratio for each components, the ones with more content may be have the content cut. Below, we use differing ratios:

// Expand ratios for the components are 1:2:3.
layout.setExpandRatio(button, i * 1.0f);

If the size of the expanding components is defined as a percentage (typically "100%"), the ratio is calculated from the overall space available for the relatively sized components. For example, if you have a 100 pixels wide layout with two cells with 1.0 and 4.0 respective expansion ratios, and both the components in the layout are set as setWidth("100%"), the cells will have respective widths of 20 and 80 pixels, regardless of the minimum size of the components.

However, if the size of the contained components is undefined or fixed, the expansion ratio is of the excess available space. In this case, it is the excess space that expands, not the components.

        for (int i = 1; i <= 3; i++) {
    // Button with undefined size.
    Button button = new Button(captions[i - 1]);
    
    layout4.addComponent(button);

    // Expand ratios are 1:2:3.
    layout4.setExpandRatio(button, i * 1.0f);
}

It is not meaningful to combine expanding components with percentually defined size and components with fixed or undefined size. Such combination can lead to a very unexpected size for the percentually sized components.

A percentual size of a component defines the size of the component within it's cell. Usually, you use "100%", but a smaller percentage or a fixed size (smaller than the cell size) will leave an empty space in the cell and align the component within the cell according to its alignment setting, top left by default.

HorizontalLayout layout50 = new HorizontalLayout();
layout50.setWidth("400px");

String[] captions1 = { "Small 50%", "Medium 50%", "Quite a big 50%" };
for (int i = 1; i <= 3; i++) {
    Button button = new Button(captions1[i-1]);
    button.setWidth("50%");
    layout50.addComponent(button);

    // Expand ratios for the components are 1:2:3.
    layout50.setExpandRatio(button, i * 1.0f);
}
parentLayout.addComponent(layout50);