实现内部动作监听器
在 Value Scroller 中，点击增值或减值按钮，输入框内的值会随之增大或者减小。我们可以简单地在组件类 ValueScroller 中实现一个内部动作监听器，重用 UICommand 的事件处理逻辑。
清单 6. 实现 Value Scroller 动作监听器
/**
* Internal action listener for Value Scroller
* _cnnew1@author cll
*
*/
private class ScrollerActionListener implements ActionListener {
public void processAction(ActionEvent e) {
// Only Integer is supported for this demo
if (input.getValue() instanceof Integer) {
String commandId = ((UICommand)e.getSource()).getId();
int value = ((Integer)input.getValue()).intValue();
// Increase value if the up link is clicked
if (commandId.equals(UPLINK_ID)) {
if (value + getStep() > max) {
input.setValue(new Integer(max));
} else {
input.setValue(new Integer(value + getStep()));
}
}
// Decrease value if the down link is clicked
else if (commandId.equals(DOWNLINK_ID)) {
if (value - getStep() < min) {
input.setValue(new Integer(min));
} else {
input.setValue(new Integer(value - getStep()));
}
}
} else {
throw new IllegalArgumentException(
"Unsupported binding type, " +
"and only Integer instance allowed for this demo.");
}
}
}
* Internal action listener for Value Scroller
* _cnnew1@author cll
*
*/
private class ScrollerActionListener implements ActionListener {
public void processAction(ActionEvent e) {
// Only Integer is supported for this demo
if (input.getValue() instanceof Integer) {
String commandId = ((UICommand)e.getSource()).getId();
int value = ((Integer)input.getValue()).intValue();
// Increase value if the up link is clicked
if (commandId.equals(UPLINK_ID)) {
if (value + getStep() > max) {
input.setValue(new Integer(max));
} else {
input.setValue(new Integer(value + getStep()));
}
}
// Decrease value if the down link is clicked
else if (commandId.equals(DOWNLINK_ID)) {
if (value - getStep() < min) {
input.setValue(new Integer(min));
} else {
input.setValue(new Integer(value - getStep()));
}
}
} else {
throw new IllegalArgumentException(
"Unsupported binding type, " +
"and only Integer instance allowed for this demo.");
}
}
}
最后，在调用 addChildrenAndFaces 方法创建添加子组件的时候，将这个自定义动作监听器添加到增值和减值组件中去。
清单 7. 注册 Value Scroller 动作监听器
ScrollerActionListener listener = new ScrollerActionListener();
upLink.addActionListener(listener);
downLink.addActionListener(listener);
upLink.addActionListener(listener);
downLink.addActionListener(listener);
