我对您的来源进行了一些更改（仍然是基本的，但它可以帮助您入门）：
- 只有 1 个公共共享状态
-
switch value change listeners 现在只需触发 state changed event
-
state changed listeners 现在会在触发时更新 UI 元素
- 注册后，
state changed listeners 会被告知（触发）当前状态
主要思想是只有一个共享状态，任何更改都会传达给所有侦听器（包括更改起源的侦听器）。
您可以在下面找到代码：（P.S. 我没有重新编译我的小部件集，所以漂亮的开关图标会退回到默认复选框样式）
1) SwitchState - 表示所有应用实例之间共享的开关状态
public enum SwitchState {
ON(true, new ThemeResource("img/on.png")), OFF(false, new ThemeResource("img/off.png"));
private final boolean value;
private final ThemeResource icon;
SwitchState(boolean value, ThemeResource icon) {
this.value = value;
this.icon = icon;
}
public boolean getValue() {
return value;
}
public ThemeResource getIcon() {
return icon;
}
public static SwitchState from(boolean value) {
return value ? ON : OFF;
}
}
2) ScrumBoard 通用状态和监听器管理器
public class ScrumBoard {
// list of listeners
private static List<SwitchChangeListener> LISTENERS = new ArrayList<>();
// initial state
private static SwitchState STATE = SwitchState.OFF;
// state change listener contract
public interface SwitchChangeListener {
void handleStateChange(SwitchState state);
}
// handle a a state change request
public static synchronized void updateState(boolean value) {
STATE = SwitchState.from(value);
fireChangeEvent(STATE);
}
// register a new state listener
public static synchronized void addSwitchChangeListener(SwitchChangeListener listener) {
System.out.println("Added listener for " + listener);
LISTENERS.add(listener);
// when a new listener is registered, also inform it of the current state
listener.handleStateChange(STATE);
}
// remove a state listener
public static synchronized void removeSwitchListener(SwitchChangeListener listener) {
LISTENERS.remove(listener);
}
// fire a change event to all registered listeners
private static void fireChangeEvent(SwitchState state) {
for (SwitchChangeListener listener : LISTENERS) {
listener.handleStateChange(state);
}
}
}
3) ScrumBoardLayout - UI 布局和组件
public class ScrumBoardLayout extends VerticalLayout implements ScrumBoard.SwitchChangeListener {
private Label icon = new Label();
private Switch mySwitch = new Switch();
public ScrumBoardLayout() {
setMargin(true);
setSpacing(true);
addHeader();
// listen for state changes
ScrumBoard.addSwitchChangeListener(this);
}
private void addHeader() {
mySwitch.setImmediate(true);
icon.setSizeUndefined();
// notify of state change
mySwitch.addValueChangeListener((Property.ValueChangeListener) event -> ScrumBoard.updateState((Boolean) event.getProperty().getValue()));
VerticalLayout layout = new VerticalLayout();
layout.setHeight("78%");
layout.addComponents(icon, mySwitch);
layout.setComponentAlignment(icon, Alignment.BOTTOM_CENTER);
layout.setComponentAlignment(mySwitch, Alignment.BOTTOM_CENTER);
layout.setExpandRatio(mySwitch, 1);
addComponents(layout);
}
@Override
public void handleStateChange(SwitchState state) {
// update UI on state change
UI.getCurrent().access(() -> {
mySwitch.setValue(state.getValue());
icon.setIcon(state.getIcon());
Notification.show(state.name(), Type.ASSISTIVE_NOTIFICATION);
});
}
@Override
public void detach() {
super.detach();
ScrumBoard.removeSwitchListener(this);
}
}
4) 结果