4

我有一个Composite. 在 SWT 中，孩子是由孩子添加的，而不是由父母添加的：

Composite parent = new Composite(shell, SWT.none);
Composite child = new Composite(parent, SWT.none);

这意味着，我不知道在父级内部，以何种方式以及何时将子级添加到父级中。

问题：

当新的孩子被添加到父母时，我需要知道在父母的内部。有没有办法注册一个onChildAddListener或任何add()方法来覆盖？

4

2 回答 2

3

添加自定义MyComposite和创建自定义ChildEvent以及ChildEventListener界面的唯一方法。MyComposite能够注册侦听器ChildEvent并在创建孩子时触发此事件Composite。

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.TypedEvent;
import org.eclipse.swt.internal.SWTEventListener;
import org.eclipse.swt.widgets.*;

/*
 * This example demonstrates the minimum amount of code required
 * to open an SWT Shell and process the events.
 */
public class HelloWorld1 {

public static void main (String [] args) {
    Display display = new Display ();
    Shell shell = new HelloWorld1 ().open (display);
    while (!shell.isDisposed ()) {
        if (!display.readAndDispatch ()) display.sleep ();
    }
    display.dispose ();
}

public Shell open (Display display) {
    Shell shell = new Shell (display);
    MyComposite parent = new MyComposite(shell, SWT.NONE);
    parent.addChildEventListener(new ChildEventListener() {

        @Override
        public void add(ChildEvent e) {
            System.out.println("Child added.");

        }
    });
    MyComposite child = new MyComposite(parent, SWT.NONE);

//  shell.open ();
    return shell;
}
}

class MyComposite extends Composite {

    ChildEventListener[] childEventListeners = new ChildEventListener[0];

    public MyComposite(Composite parent, int style) {
        super(parent, style);
        if (parent instanceof MyComposite){
            ((MyComposite)parent).fireChildEvent(new ChildEvent(this));
        }
    }
    public void addChildEventListener (ChildEventListener listener) {
        checkWidget();
        if (listener == null) SWT.error (SWT.ERROR_NULL_ARGUMENT);
        ChildEventListener[] newChildEventListeners = new ChildEventListener[childEventListeners.length + 1];
        System.arraycopy(childEventListeners, 0, newChildEventListeners, 0, childEventListeners.length);
        childEventListeners = newChildEventListeners;
        childEventListeners[childEventListeners.length - 1] = listener;
    }
    public void removeChildEventListener (ChildEventListener listener) {
        if (childEventListeners.length == 0) return;
        int index = -1;
        for (int i = 0; i < childEventListeners.length; i++) {
            if (listener == childEventListeners[i]){
                index = i;
                break;
            }
        }
        if (index == -1) return;
        if (childEventListeners.length == 1) {
            childEventListeners = new ChildEventListener[0];
            return;
        }
        ChildEventListener[] newChildEventListeners = new ChildEventListener[childEventListeners.length - 1];
        System.arraycopy (childEventListeners, 0, newChildEventListeners, 0, index);
        System.arraycopy (childEventListeners, index + 1, newChildEventListeners, index, childEventListeners.length - index - 1);
        childEventListeners = newChildEventListeners;
    }
    public void fireChildEvent(ChildEvent event){
        for (int i = 0; i < childEventListeners.length; i++) {
            childEventListeners[i].add (event);
        }

    }
}

interface ChildEventListener extends SWTEventListener {
    public void add(ChildEvent e);
}

class ChildEvent extends TypedEvent {

    public ChildEvent(Widget widget) {
        super(widget);
        // TODO Auto-generated constructor stub
    }

}
于 2012-08-25T14:09:40.050 回答
1

我想了解添加子项的目的是在将子项添加到使用特定布局（例如）进行布局的子项时对子项进行布局（添加例如LayoutData）。GridDataGridLayout

由于无法在添加时布局子级 - 在每个小部件调整大小时检查其布局：

    /*
     * To make the forms fill the group - laying out the children is necessary.
     * Unfortunately it is not possible to listen for children addition, in order to layout the children addition automatically.
     * This means that the user will have to remember  to layout the children, which is a nogo.
     * 
     * Solution: 
     * istead of adding right layout on child addition -  check if there are new children every time the widget is resized.
     * if a widget without layoutData is found (new child not layed out) - add a layout
     */
    this.addControlListener(new ControlAdapter() {
        @Override
        public void controlResized(ControlEvent e) {
            layoutChildren();
        }
    });
}
private void layoutChildren(){
    for(Control child:getChildren()){
        if(child.getLayoutData() == null){
            child.setLayoutData(new GridData(SWT.FILL, SWT.CENTER, true, false, 1, 1)); 
        }
    }
}

public void addToGroup(Composite child){
    child.setLayoutData(new GridData(SWT.FILL, SWT.CENTER, true, false, 1, 1));
}
于 2014-08-20T13:15:11.110 回答