再说SWT中的滚动面板ScrolledComposite实现

记得以前写过一篇关于滚动面板的文章 SWT中 ScrolledComposite 滚动面板 “不可用” 等常见问题的简单解释，最近又需要实现一个滚动的composite的效果，
当然还是想到了ScrolledComposite，不过看过源码后，对其理解又更加深了一下，其源码的注释中提供的例子代码，是极好的，掠过来看看：

public static void main (String [] args) {
      Display display = new Display ();
      Color red = display.getSystemColor(SWT.COLOR_RED);
      Color blue = display.getSystemColor(SWT.COLOR_BLUE);
      Shell shell = new Shell (display);
      shell.setLayout(new FillLayout());//关键点1.外层的容器layout为FillLayout
 	
      // set the size of the scrolled content - method 1
      final ScrolledComposite sc1 = new ScrolledComposite(shell, SWT.H_SCROLL | SWT.V_SCROLL | SWT.BORDER);
      final Composite c1 = new Composite(sc1, SWT.NONE);
      sc1.setContent(c1);//关键点2.设置Scrolled容器的Content为内层的容器
      c1.setBackground(red);
      GridLayout layout = new GridLayout();
      layout.numColumns = 4;
      c1.setLayout(layout);
      Button b1 = new Button (c1, SWT.PUSH);
      b1.setText("first button");
      c1.setSize(c1.computeSize(SWT.DEFAULT, SWT.DEFAULT));//关键点3
      
      // set the minimum width and height of the scrolled content - method 2
      final ScrolledComposite sc2 = new ScrolledComposite(shell, SWT.H_SCROLL | SWT.V_SCROLL | SWT.BORDER);
      sc2.setExpandHorizontal(true);
      sc2.setExpandVertical(true);
      final Composite c2 = new Composite(sc2, SWT.NONE);
      sc2.setContent(c2);
      c2.setBackground(blue);
      layout = new GridLayout();
      layout.numColumns = 4;
      c2.setLayout(layout);
      Button b2 = new Button (c2, SWT.PUSH);
      b2.setText("first button");
      sc2.setMinSize(c2.computeSize(SWT.DEFAULT, SWT.DEFAULT));
      
      Button add = new Button (shell, SWT.PUSH);
      add.setText("add children");
      final int[] index = new int[]{0};
      add.addListener(SWT.Selection, new Listener() {
          public void handleEvent(Event e) {
              index[0]++;
              Button button = new Button(c1, SWT.PUSH);
              button.setText("button "+index[0]);
              // reset size of content so children can be seen - method 1
              c1.setSize(c1.computeSize(SWT.DEFAULT, SWT.DEFAULT));
              c1.layout();
              
              button = new Button(c2, SWT.PUSH);
              button.setText("button "+index[0]);
              // reset the minimum width and height so children can be seen - method 2
              sc2.setMinSize(c2.computeSize(SWT.DEFAULT, SWT.DEFAULT));
              c2.layout();
          }
      });
 
      shell.open ();
      while (!shell.isDisposed ()) {
          if (!display.readAndDispatch ()) display.sleep ();
      }
      display.dispose ();
 }

有了这个例子（注意有两种不同的实现方式哦），正确快速的实现滚动面板，那就是三下五除二的事情了。最后，还是那句话，源码是最好的文档，多多看开源项目的源码，尤其是Eclipse的，这样不但能更快的了解其Api，而且其中的好多设计方法和设计思想也是值得我们借鉴和学习的。