tasklist.java

Java程序设计技巧与开发实例附书源代码。

import java.awt.*;
import java.awt.event.*;

public class TaskList
    extends Frame
    implements ActionListener {
  private Button add = new Button("Add");
  private Button del = new Button("Delete");
  private Button up = new Button(" + ");
  private Button down = new Button("－");
  private List list = new List();
  private TextField taskInput = new TextField();
  private Label priorityLabel = new Label("改变优先级");
  private Label taskLabel = new Label("任务：");

  private class WindowCloser
      extends WindowAdapter {
    public void windowClosing(WindowEvent we) {
      System.exit(0);
    }
  }

  public TaskList() {
    //构造方法定义布局和激活按钮
    super("Task List");
    setup();
    add.addActionListener(this);
    del.addActionListener(this);
    up.addActionListener(this);
    down.addActionListener(this);
    addWindowListener(new WindowCloser());
    pack();
    show();
  }

  public void actionPerformed(ActionEvent ae) {
    //按下按钮后的反应

    if ( (ae.getSource() == add) && (!taskInput.getText().equals(""))) {
      handleAdd(taskInput.getText().trim());
    }
    else if ( (ae.getSource() == del) && (list.getSelectedIndex() >= 0)) {
      handleDel(list.getSelectedIndex());
    }
    else if ( (ae.getSource() == up) && (list.getSelectedIndex() > 0)) {
      handleIncPriority(list.getSelectedIndex());
    }
    else if ( (ae.getSource() == down) && (list.getSelectedIndex() >= 0)) {
      handleDecPriority(list.getSelectedIndex());
    }
    taskInput.requestFocus();

  }

  private void handleAdd(String newTask) {
    list.add(newTask);
    list.select(list.getItemCount() - 1);
    taskInput.setText("");
  }

  private void handleDel(int pos) {
    list.remove(pos);
    list.select(pos);
  }

  private void handleIncPriority(int pos) {
    String item = list.getItem(pos);
    list.remove(pos);
    list.add(item, pos - 1);
    list.select(pos - 1);
  }

  private void handleDecPriority(int pos) {
    if (pos < list.getItemCount() - 1) {
      String item = list.getItem(pos);
      list.remove(pos);
      list.add(item, pos + 1);
      list.select(pos + 1);
    }
  }

  private void setup() {
    Panel buttons = new Panel();
    buttons.setLayout(new FlowLayout());
    buttons.add(add);
    buttons.add(del);
    Panel priorities = new Panel();
    priorities.setLayout(new FlowLayout());
    priorities.add(up);
    priorities.add(priorityLabel);
    priorities.add(down);
    Panel input = new Panel();
    input.setLayout(new BorderLayout());
    input.add("West", taskLabel);
    input.add("Center", taskInput);
    Panel top = new Panel();
    top.setLayout(new GridLayout(2, 1));
    top.add(input);
    top.add(priorities);
    setLayout(new BorderLayout());
    add("Center", list);
    add("South", buttons);
    add("North", top);
  }

  public static void main(String args[]) {
    TaskList tl = new TaskList();
  }
}