SWT 自定义布局

在上篇文章中我们介绍了swt的四大布局，通过代码我们可以发现4种布局都是继承与一个Layout抽象父类，那我们是不是可以自己通过继承Layout写一个属于自己的布局呢，答案是肯定，下面我来介绍一个自己写布局，BorderLayout 此布局一次至多现实5个子控件，分别指定，top bottom left right center control 来完成布局下面是其源码

 public class BorderLayout extends Layout {
   	 	public int marginWidth = 0;
   	 	public int marginHeight = 0;
   	 	public Control topControl;
   	 	public Control bottomControl;
   	 	public Control rightControl;
   	 	public Control leftControl;
   	 	public Control centerControl;
   	 	Point computeSize (Control control, boolean flushCache) {
   	 		int wHint = SWT.DEFAULT, hHint = SWT.DEFAULT;
   	 		return control.computeSize (wHint, hHint, flushCache);
   	 	}
        @Override
		protected Point computeSize(Composite composite, int wHint, int hHint,
                boolean flushCache) {
        	int topHeight=0;
        	int bottomHeight=0;
        	int centerHeight=0;
        	int leftWidth=0;
        	int centerWidth=0;
        	int rightWidth=0;
        	if(topControl!=null){
        		Point size = computeSize(topControl, flushCache);
        		topHeight=size.y;
        		centerWidth=Math.max(size.x, centerWidth);
        	}
        	
        	if(centerControl!=null){
        		Point size= computeSize(centerControl, flushCache);
        		centerHeight=Math.max(size.y,centerHeight);
        		centerWidth=Math.max(size.x, centerWidth);
        	}
        	if(leftControl!=null){
        		Point size= computeSize(leftControl, flushCache);
        		centerHeight=Math.max(size.y,centerHeight);
        		leftWidth=size.x;
        	}
        	if(rightControl!=null){
        		Point size= computeSize(rightControl, flushCache);
        		centerHeight=Math.max(size.y,centerHeight);
        		rightWidth=size.x;
        	}
        	
        	if(bottomControl!=null){
        		Point size= computeSize(bottomControl, flushCache);
        		bottomHeight=size.y;
        		centerWidth=Math.max(size.x, centerWidth);
        	}
        	int height=topHeight+centerHeight+bottomHeight+2 * marginWidth;
        	int width=leftWidth+centerWidth+rightWidth+2 * marginHeight;
        	if (wHint != SWT.DEFAULT) width = wHint;
        	if (hHint != SWT.DEFAULT) height = hHint;
        	return new Point(width, height);
         
        }

        @Override
		protected boolean flushCache(Control control) {
			// TODO Auto-generated method stub
			return true;
		}

		@Override
		protected void layout(Composite composite, boolean flushCache) {
			Rectangle rect = composite.getClientArea();
			rect.x += marginWidth;
			rect.y += marginHeight;
			rect.width -= 2 * marginWidth;
			rect.height -= 2 * marginHeight;
	        if(topControl!=null){
	    		Point size = computeSize(topControl, flushCache);
	    		Rectangle top_rect=new Rectangle(rect.x+(rect.width-size.x)/2 ,rect.y, size.x,size.y);
	    		topControl.setBounds(top_rect);
	    		
	    	}
	    	if(centerControl!=null){
	    		Point size= computeSize(centerControl, flushCache);
	    		Rectangle center_rect=new Rectangle(rect.x+(rect.width-size.x)/2 ,rect.y+(rect.height-size.y)/2, size.x,size.y);
	    		centerControl.setBounds(center_rect);
	    	}
	    	if(leftControl!=null){
	    		Point size= computeSize(leftControl, flushCache);
	    		Rectangle left_rect=new Rectangle(rect.x ,rect.y+(rect.height-size.y)/2, size.x,size.y);
	    		leftControl.setBounds(left_rect);
	    	}
	    	if(rightControl!=null){
	    		Point size= computeSize(rightControl, flushCache);
	    		Rectangle right_rect=new Rectangle(rect.x+rect.width-size.x ,rect.y+(rect.height-size.y)/2, size.x,size.y);
	    		rightControl.setBounds(right_rect);
	    	}
	    	
	    	if(bottomControl!=null){
	    		Point size= computeSize(bottomControl, flushCache);
	    		Rectangle bottom_rect=new Rectangle(rect.x+(rect.width-size.x)/2 ,rect.y+(rect.height-size.y), size.x,size.y);
	    		bottomControl.setBounds(bottom_rect);
	    	}
		}
    }

在下面是其应用代码：

BorderLayout bl=new BorderLayout();
		shell.setLayout(bl);
		Button top_b=new Button(shell,SWT.PUSH);
		top_b.setText("top");
		bl.topControl=top_b;
		Button bottom_b=new Button(shell,SWT.PUSH);
		bottom_b.setText("bottom");
		bl.bottomControl=bottom_b;
		Button left_b=new Button(shell,SWT.PUSH);
		left_b.setText("left");
		bl.leftControl=left_b;
		Button right_b=new Button(shell,SWT.PUSH);
		right_b.setText("right");
		bl.rightControl=right_b;
		Button center_b=new Button(shell,SWT.PUSH);
		center_b.setText("center");
		bl.centerControl=center_b;

接下来是其UI效果图

其实在swt库中，还有很多其他layout只是用的比较少，现在我在为大家介绍一种我在实际情况中用的比较多的一个：StackLayout

此布局一次只能显示一个子控件，通过它的一个属性topControl 用此我们可以做一个类似卡片一样的控件，通过点击它显示的子控件，来更换控件，下面是具体代码：

StackLayout sl=new StackLayout();
shell.setLayout(sl);
for(int i=0;i<5;i++){
	Button b=new Button(shell,SWT.PUSH);
	b.setText("button"+i);
	b.setData(i);
	if(i==0){
		sl.topControl=b;
	}
	b.addSelectionListener(new SelectionListener() {
				
		@Override
		public void widgetSelected(SelectionEvent e) {
			// TODO Auto-generated method stub
					
			for(Control c:shell.getChildren()){
				int index=(int) b.getData();
				if(index<4){
					index++;
					if(index==(int)c.getData()){
						sl.topControl=c;
						shell.layout();
						break;
					}
				}else{
					if(0==(int)c.getData()){
						sl.topControl=c;
						shell.layout();
						break;
					}
				}
			}
		}
				
		@Override
		public void widgetDefaultSelected(SelectionEvent e) {
			// TODO Auto-generated method stub
					
		}
	});
}

窗口刚打开效果如图：

按钮点击一下的效果如下，以此类推

想要知道更多swt库中以后的布局，可以查询Layout的子类，谢谢大家

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