问题描述
是否可以使用 Vaadin 处理 MouseDown/MouseUp 和 KeyDown/KeyUp 事件?我发现 论坛主题 有同样的问题，看起来答案是否定的，但那是 5 年前的事了——我希望以后的版本能有所改变.我仍然在 API 中找不到任何东西.也许有一些解决方法可以拦截此类事件?
Is it possible to handle MouseDown/MouseUp and KeyDown/KeyUp evens with Vaadin? I've found forum thread with the same question and looks like the answer is no, but it was 5 years ago - I hope something changed with later releases. Still I can't find anything in API. Maybe there's some workaround for intercepting such evens?
推荐答案
好吧，几天后我想出了可接受的(对我来说)解决方案.必需的组件必须用扩展拦截器包装(感谢@petey 在评论中的想法)，里面有 KeyDownHandler.但是诀窍不是添加到组件本身(因为它可能会错过触发)，而是添加到 RootPanel.所以这是一个有效的例子.
Well, after couple of days I came up with the acceptable (for me) solution. Required component has to be wrapped with extension-interceptor (credits to @petey for an idea in the comments) with KeyDownHandler inside. But the trick is not to add to the component itself (because it can miss triggering), but to the RootPanel. So here's a working example.
扩展:
public class InterceptorExtension extends AbstractExtension {
private boolean shiftKeyDown;
public InterceptorExtension(Tree tree) {
super.extend(tree);
registerRpc((InterceptorExtensionServerRpc) state -> shiftKeyDown = state);
}
public boolean isShiftKeyDown() {
return shiftKeyDown;
}
}
ServerRpc:
public interface InterceptorExtensionServerRpc extends ServerRpc {
void setShiftKeyDown(boolean state);
}
连接器:
@Connect(InterceptorExtension.class)
public class InterceptorExtensionConnector extends AbstractExtensionConnector {
@Override
protected void extend(final ServerConnector target) {
final InterceptorExtensionServerRpc rpcProxy = getRpcProxy(InterceptorTreeExtensionServerRpc.class);
final RootPanel rootPanel = RootPanel.get();
rootPanel.addDomHandler(new KeyDownHandler() {
@Override
public void onKeyDown(KeyDownEvent event) {
if (event.isShiftKeyDown()) {
rpcProxy.setShiftKeyDown(true);
}
}
}, KeyDownEvent.getType());
rootPanel.addDomHandler(new KeyUpHandler() {
@Override
public void onKeyUp(KeyUpEvent event) {
if (!event.isShiftKeyDown()) {
rpcProxy.setShiftKeyDown(false);
}
}
}, KeyUpEvent.getType());
}
}
然后，您可以随时通过 InterceptorExtension#isShiftKeyDown 在服务器端获得 Shift 按钮状态.
Then whenever you want you can get Shift-button state on the server-side via InterceptorExtension#isShiftKeyDown.
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