列表组件的应用举例

When doing homework, I didn't do a lot of homework about list components because of lack of time. He carefully read this example in the book, output and run 1 to import Java. awt。 *; 2 import Java. awt。 Events. *; 3 public classtasklistendsframements actionlistener 4 {5 privatebuttonadd=newbutton (style=' color:rgba (0,0,1)'' add''); 6privateButtondel=newButton ('delete'); 7privateButtonup=newButton ('increase priority'); 8privateButtondown=newButton ('reduce priority'); 9 private list

=new List();
 10    private TextField taskInput=new TextField();
 11    private Label priorityLabel=new Label("改变优先级");
 12    private Label taskLabel=new Label("工作事项:");
 13    private class WindowCloser extends WindowAdapter
 14    {
 15        public void windowClosing(WindowEvent we)
 16        {
 17            System.exit(0);
 18        }
 19    }
 20    public TaskList()
 21    {
 22        super("工作事项表");
 23        setup();
 24        add.addActionListener(this);
 25        del.addActionListener(this);
 26        down.addActionListener(this);
 27        up.addActionListener(this);
 28        list.addActionListener(this);
 29        addWindowListener(new WindowCloser());
 30        pack();
 31        show();
 32    }
 33    private void setup()
 34    {
 35        Panel buttons=new Panel();
 36        buttons.setLayout(new FlowLayout());
 37        buttons.add(add);     
 38        buttons.add(del);
 39        Panel priorities=new Panel();
 40        priorities.setLayout(new FlowLayout());
 41        priorities.add(up);
 42        priorities.add(priorityLabel);
 43        priorities.add(down);
 44        Panel input=new Panel();
 45        input.setLayout(new BorderLayout());
 46        input.add("West",taskLabel);
 47        input.add("Center",taskInput);
 48        Panel top=new Panel();
 49        top.setLayout(new GridLayout(2,1));
 50        top.add(input);
 51        top.add(priorities);
 52        setLayout(new BorderLayout());
 53        add("Center",list);
 54        add("South",buttons);
 55        add("North",top);
 56    }
 57    public void actionPerformed(ActionEvent ae)
 58    {
 59        if((ae.getSource()==add)&&(!taskInput.getText().equals("")))
 60            handleAdd(taskInput.getText().trim());   //public String trim():删除该字符串两端的空格。
 61        if((ae.getSource()==del)&&(list.getSelectedIndex()>=0))  //getSelectedIndex():获取列表中选定项的下标
 62            handleDel(list.getSelectedIndex());
 63        if((ae.getSource()==up)&&(list.getSelectedIndex()>=0))
 64            handleIncPriority(list.getSelectedIndex());
 65        if((ae.getSource()==down)&&(list.getSelectedIndex()>=0))
 66            handleDecPriority(list.getSelectedIndex());
 67        if((ae.getSource()==list))
 68            taskInput.setText(list.getSelectedItem());
 69        taskInput.requestFocus();
 70    }
 71    private void handleAdd(String newTask)
 72    {
 73        list.add(newTask);  //add(String item):在滚动列表的末尾添加指定项
 74        list.select(list.getItemCount()-1);//getItemCount()获取列表的项数;
 75        taskInput.setText("");//select(int index)选择滚动列表中指定下标的项
 76    }
 77    private void handleDel(int pos)
 78    {
 79        list.remove(pos);//remove(int position)从此列表中删除指定位置的某项
 80        list.select(pos);
 81    }
 82    private void handleIncPriority(int pos)
 83    {
 84        String item=list.getItem(pos);
 85        list.remove(pos);
 86        list.add(item,pos-1);
 87        list.select(pos-1);
 88    }
 89    private void handleDecPriority(int pos)
 90    {
 91        if(pos<list.getItemCount()-1)
 92        {
 93            String item=list.getItem(pos);
 94            list.remove(pos);
 95            list.add(item,pos+1);
 96            list.select(pos+1);
 97        }
 98    }
 99    public static void main(String[] args) 
100    {
101        TaskList t=new TaskList();
102    }
103}
104