java - SWT 标签在处置和重新创建后不显示

Question

在以下代码中，单击三个显示列表按钮之一将首先处理组合中的所有标签，然后为字符串列表中的每一行创建标签。

问题是，如果您第二次单击同一按钮，文本就会全部消失。

当您切换到其他按钮之一并显示文本时。

代码每次都会执行相同的操作，即处理组合内的所有标签，然后将新标签添加到组合中，似乎会发生的情况是，如果您将具有完全相同内容的标签添加回组合中，那么它由于某种原因不再在屏幕上显示它们。

import java.util.ArrayList;
import java.util.List;

import org.eclipse.jface.dialogs.Dialog;
import org.eclipse.swt.SWT;
import org.eclipse.swt.events.SelectionAdapter;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.graphics.Point;
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.Control;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.widgets.Shell;

public class BasicMapLabelTestDialog extends Dialog
{
    List<Label> displaylabels = new ArrayList<>();
    Composite content, list;
    
    public BasicMapLabelTestDialog(Shell parentShell)
    {
        super(parentShell);
    }

    @Override
    protected void configureShell(Shell shell)
    {
        super.configureShell(shell);
        shell.setSize(new Point(700, 500));
        shell.setText("FML"); //$NON-NLS-1$
    }

    @Override
    public Control createDialogArea(final Composite comp)
    {
        content = (Composite) super.createDialogArea(comp);
        content.setLayout(new GridLayout(1, false));
        content.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true)); 
        
        
        final List<String> rows1 = new ArrayList<>(3);
        rows1.add("Hello");
        rows1.add("Baz");
        rows1.add("Please");
        rows1.add("Help");
        
        final List<String> rows2 = new ArrayList<>(3);
        rows2.add("You're");
        rows2.add("My");
        rows2.add("Only");
        rows2.add("Hope");
        
        
        final List<String> rows3 = new ArrayList<>(3);
        rows3.add("Or");
        rows3.add("Maybe");
        rows3.add("greg?");
        
        
        
        Button set1 = new Button(content, SWT.PUSH);
        set1.setText("Display List 1");
        set1.addSelectionListener(new SelectionAdapter() {
            
            @Override
            public void widgetSelected(SelectionEvent e) {
                updateList(rows1);
            }
        });
                
        
        Button set2 = new Button(content, SWT.PUSH);
        set2.setText("Display List 2");           
        set2.addSelectionListener(new SelectionAdapter() {
            
            @Override
            public void widgetSelected(SelectionEvent e) {
                updateList(rows2);
            }
        });
        
        Button set3 = new Button(content, SWT.PUSH);
        set3.setText("Display List 3");           
        set3.addSelectionListener(new SelectionAdapter() {
            
            @Override
            public void widgetSelected(SelectionEvent e) {
                updateList(rows3);
            }
        });
        
        
        Button test = new Button(content, SWT.PUSH);
        test.setText("Print Label Content");           
        test.addSelectionListener(new SelectionAdapter() {
            
            @Override
            public void widgetSelected(SelectionEvent e) {
                for (Label l : displaylabels) {
                    System.out.println(l.getText());
                }
            }
        });
        
        
        
        list = new Composite(content, SWT.NONE);
        list.setLayout(new GridLayout(1, true));
        new Label(content, SWT.HORIZONTAL | SWT.SEPARATOR);
        

        return content;
    }
    
    private void updateList(List<String> rows) {
        if (this.displaylabels == null) {
            this.displaylabels = new ArrayList<>();
        }
        for (Label l : displaylabels) {
            l.dispose();
        }
        this.displaylabels.clear();


        for (String item : rows) {
            addListLabel(item);
        }
        
        content.layout();
        content.redraw();
    }
    
    private void addListLabel(String whoText) {
        Label a = new Label(list, SWT.NONE);
        a.setText(whoText);
        this.displaylabels.add(a);
    }
    
    public static void main(String[] args)
    {
        Display d = new Display();
        Shell s = new Shell();

        BasicMapLabelTestDialog fml = new BasicMapLabelTestDialog(s);
        fml.open();
    }
    
}

Answer 1

调用

content.layout();

不足以在这里进行完整的布局。您需要调用

content.layout(true, true);

强制布置所有控件。

您不需要 redraw 调用。