[SWT] Make the content in ScrolledComposite still scrollable after dynamic changes

Introduction:
In user interface design, sometimes it is necessary to display a large amount of content in a limited space. If the content exceeds the size of the viewable area, the scroll feature helps the user scroll and see all the content. This article will introduce how to use the ScrolledComposite control in the Eclipse SWT library to display scrollable labels in the scroll area.

Problem Description

Suppose you have an interface that contains a button and a scroll area. When the user clicks the button, he hopes to add a new label in the scroll area, and if the number of labels exceeds the visible area size of the scroll area, the user can scroll through all labels through the scroll bar.

solution

In Eclipse SWT, a ScrolledComposite is a scrollable container control that can contain other controls and provide scrolling capabilities.

Here is sample code:


import org.eclipse.swt.SWT;
import org.eclipse.swt.custom.ScrolledComposite;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.widgets.Shell;

public class DynamicContentExample {
    
    

    public static void main(String[] args) {
    
    
        Display display = new Display();
        Shell shell = new Shell(display);
        shell.setMinimumSize(300, 360);	
        shell.setLayout(new GridLayout());

        Button addButton = new Button(shell, SWT.PUSH);
        addButton.setText("Add Content");
        
        // draw ScrolledComposite
        ScrolledComposite scrolledComposite = new ScrolledComposite(shell, SWT.V_SCROLL);
        scrolledComposite.setExpandVertical(true);
        scrolledComposite.setLayoutData(new GridData(GridData.FILL_BOTH));

        Composite contentComposite = new Composite(scrolledComposite, SWT.NONE);
        contentComposite.setLayout(new GridLayout(1, false));
        contentComposite.setLayoutData(new GridData(GridData.FILL_BOTH));

        scrolledComposite.setContent(contentComposite);
        scrolledComposite.setMinSize(contentComposite.computeSize(scrolledComposite.getClientArea().width, SWT.DEFAULT));

        // add event
        addButton.addListener(SWT.Selection, event -> {
    
    
            // 添加新内容
            Label label = new Label(contentComposite, SWT.NONE);
            label.setText("New Label");

            contentComposite.layout();
            contentComposite.setSize(contentComposite.computeSize(SWT.DEFAULT, SWT.DEFAULT));

            scrolledComposite.setMinSize(contentComposite.computeSize(scrolledComposite.getClientArea().width, SWT.DEFAULT));
        });
        
        shell.pack();
        shell.open();

        while (!shell.isDisposed()) {
    
    
            if (!display.readAndDispatch()) {
    
    
                display.sleep();
            }
        }

        display.dispose();
    }
}

In the sample code, the ScrolledComposite control from the Eclipse SWT library is used to implement the scrolling area. When the user clicks the "Add Content" button, a new Label control is created and added to the content Composite. Then, update the ScrolledComposite by recalculating the size and setting the minimum size so that it scrolls through all the labels.

Note addButton.addListenerthe important code


// 内容容器重新布局
contentComposite.layout();
// 内容容器重新计算大小
contentComposite.setSize(contentComposite.computeSize(SWT.DEFAULT, SWT.DEFAULT));


// 给滚动容器重新指定最小值
scrolledComposite.setMinSize(contentComposite.computeSize(scrolledComposite.getClientArea().width, SWT.DEFAULT));

Effect

Initial:
insert image description here
After adding some content:

insert image description here

When the added content exceeds the size of the visible area, a scroll bar appears on the right:

insert image description here

in conclusion

By using Eclipse SWT's ScrolledComposite control, you can display scrollable content in a scroll area. This technique is useful for user interfaces that need to display a large amount of content in a limited space. The sample code can be extended as needed and customized to meet specific design requirements.