Java的奇怪想象

[hjxaut]

我的程序如下：
package hj.com;

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.KeyAdapter;
import org.eclipse.swt.events.KeyEvent;
import org.eclipse.swt.events.KeyListener;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.List;
import org.eclipse.swt.widgets.Shell;

public class testList {

protected Shell shell;

/**
* Launch the application
* @param args
*/
public static void main(String[] args) {
try {
testList window = new testList();
window.open();
} catch (Exception e) {
e.printStackTrace();
}
}

/**
* Open the window
*/
public void open() {
final Display display = Display.getDefault();
createContents();
shell.open();
shell.layout();
while (!shell.isDisposed()) {
if (!display.readAndDispatch())
display.sleep();
}
}

/**
* Create contents of the window
*/
protected void createContents() {
shell = new Shell();
shell.setSize(500, 375);
shell.setText("SWT Application");

final List list=new List(shell,SWT.BORDER);
// list.select(0);
list.setItems(new String[]{"第0","第1","第2","第3","第4"});
list.setBounds(0,0,50,200);
list.setSelection(0);

list.addKeyListener(new KeyAdapter(){
public void keyPressed(KeyEvent e){
int curIndex=list.getSelectionIndex();
int total=list.getItemCount();

if(e.keyCode==SWT.ARROW_UP){
if(curIndex==0){
list.select(total-1);
int c=list.getSelectionIndex();
System.out.println(c);
}
}else if(e.keyCode==SWT.ARROW_DOWN){
if(curIndex==total-1){
list.select(0);
int c=list.getSelectionIndex();
System.out.println(c);
}
}
}



});

//
}

}
我的功能是当按光标向下时，LISH中被选中的item依次下移，但是当移到最后一项时，则重新选择第一项。但上述程序当移动到最后一项，却选择第二项而不是第一项，这是为什么呢？？

[老紫竹]

我想有一个问题，你每次按向下的时候，我并没有看到你移动index的代码
也就是说，这个组件会自动向下移动。
如果这样的话，你应该选中-1的位置，这样组件自动下移的时候，就会变成选中了0

list.select(-1);

[老紫竹]

Sorry!虽然现象估计准确，但不知道怎么屏蔽默认的移动。楼上的代码无效！！

[老紫竹]

总算实现了，增加了一个记录上一个位置的变量，请参考

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.KeyAdapter;
import org.eclipse.swt.events.KeyEvent;
import org.eclipse.swt.events.KeyListener;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.List;
import org.eclipse.swt.widgets.Shell;

public class TestList {
  protected Shell shell;

  /**
   * Launch the application
   * 
   * @param args
   */
  public static void main(String[] args) {
    try {
      TestList window = new TestList();
      window.open();
    } catch (Exception e) {
      e.printStackTrace();
    }
  }

  /**
   * Open the window
   */
  public void open() {
    final Display display = Display.getDefault();
    createContents();
    shell.open();
    shell.layout();
    while (!shell.isDisposed()) {
      if (!display.readAndDispatch())
        display.sleep();
    }
  }

  /**
   * Create contents of the window
   */
  protected void createContents() {
    shell = new Shell();
    shell.setSize(500, 375);
    shell.setText("SWT Application");
    final List list = new List(shell, SWT.BORDER | SWT.V_SCROLL);
    // list.select(0);
    list.setItems(new String[] { "第0", "第1", "第2", "第3", "第4" });
    list.setBounds(0, 0, 50, 200);
    list.setSelection(0);
    list.addKeyListener(new KeyAdapter() {
      int lastIndex = -1;

      public void keyReleased(KeyEvent e) {
        int curIndex = list.getSelectionIndex();
        System.out.println("c=" + curIndex);
        int total = list.getItemCount();
        if (e.keyCode == SWT.ARROW_UP) {
          if (lastIndex == 0) {
            list.select(total - 1);
            curIndex = total-1;
            list.showSelection();
            int c = list.getSelectionIndex();
            System.out.println(c);
          }
        } else if (e.keyCode == SWT.ARROW_DOWN) {
          if (lastIndex == total - 1) {
            list.select(0);
            curIndex = 0;
            list.showSelection();
            int c = list.getSelectionIndex();
            System.out.println(c);
          }
        }
        lastIndex = curIndex;
      }
    });
    //  
  }
}