标题 这Date_selector_panel是重要部分。现在我们来看看他的装饰。Titled_date_selector类只做一件事情:给未装饰的日历增加个标题。
作者:中国IT实验室 来源:中国IT实验室 2007年8月26日
关键字:
NAVIGATION/导航
下面展示的就是导航栏的实现代码,虽然有点长,但同样非常地简单。代码由定义了4个图象文件的代码开始。(我计划以后放弃箭头采用代码实现,但是现在仍然在用图象文件。)用下面的代码,把图象作为资源获取过来。
ClassLoader loader = getClass().getClassLoader();
loader.getResource( "IMAGE_FILE_NAME" );
classloader在找类的地方找图象资源;比如,程序在文件系统中运行,它将要在classpath中查找文件路径。因为没有用到绝对路径,代码是更加容易的打包成jar文件,并且文件也不再需要建立在文件系统中。导航栏是一个四个用图象做标签的按纽,按纽的动作监听通过Date_selector的roll()来包装日历对象,并且月份的改变也激发标题栏的改变。有一点非常重要就是导航条不知道也不影响标题。标题包装器是一个监听,所以它能自动的更新标题。导航条根本就不知道标题包装器的存在。
public class Navigable_date_selector extends JPanel implements Date_selector
{ private Date_selector selector;
// Names of image files used for the navigator bar
private static final String
NEXT_YEAR = "images/10px.red.arrow.right.double.gif",
NEXT_MONTH = "images/10px.red.arrow.right.gif",
PREVIOUS_YEAR = "images/10px.red.arrow.left.double.gif",
PREVIOUS_MONTH = "images/10px.red.arrow.left.gif";
// These constants are used to identify the button and
// as the button caption in the event that the appropriate
// image file can't be located
private static final String FORWARD_MONTH = ">" ,
FORWARD_YEAR = ">>" ,
BACK_MONTH = "<" ,
BACK_YEAR = "<<"
private JPanel navigation = new JPanel();
public Navigable_date_selector( Date_selector selector )
{ this.selector = selector;
setBorder( null );
setOpaque( false );
setLayout( new BorderLayout() );
add( (JPanel)selector, BorderLayout.CENTER );
navigation.setLayout(new FlowLayout());
navigation.setBorder( null );
navigation.setBackground( com.holub.ui.Colors.LIGHT_YELLOW );
navigation.add( make_navigation_button(BACK_YEAR ) );
navigation.add( make_navigation_button(BACK_MONTH ) );
navigation.add( make_navigation_button(FORWARD_MONTH) );
navigation.add( make_navigation_button(FORWARD_YEAR ) );
add(navigation, BorderLayout.SOUTH);
}
// ...
// I left out a few constructors and utility methods that go here
// ...
private final Navigation_handler navigation_listener
= new Navigation_handler();
/** Handle clicks from the navigation bar buttons */
private class Navigation_handler implements ActionListener
{ public void actionPerformed(ActionEvent e)
{ String direction = e.getActionCommand();
if (direction==FORWARD_YEAR )selector.roll(Calendar.YEAR,true);
else if(direction==BACK_YEAR )selector.roll(Calendar.YEAR,false);
else if(direction==FORWARD_MONTH)
{
selector.roll(Calendar.MONTH,true);
if( selector.get(Calendar.MONTH) == Calendar.JANUARY )
selector.roll(Calendar.YEAR,true);
}
else if (direction==BACK_MONTH )
{
selector.roll(Calendar.MONTH,false);
if( selector.get(Calendar.MONTH) == Calendar.DECEMBER )
selector.roll(Calendar.YEAR,false);
}
else
{ assert false: "Unexpected direction";
}
}
}
private JButton make_navigation_button(String caption)
{
ClassLoader loader = getClass().getClassLoader();
URL image =
(cap