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GWT:TextField的拖放事件?

[英]GWT: Drag&Drop Event for TextField?

I wonder how it is possible to listen for the drop event for a TextField . 我想知道如何监听TextField的drop事件。 I need to intercept that events in order to do value checks. 我需要拦截该事件以便进行值检查。

I wrote an extended TextBox , which fires TextChangeEvents . 我写了一个扩展的TextBox ,它触发了TextChangeEvents But when i drop a text into the text field, I don't get a call for the onBrowserEvent(Event event) method. 但是,当我将文本放入文本字​​段时,我没有调用onBrowserEvent(Event event)方法。

Any hint? 有什么提示吗?

public class ExtendedTextBox extends TextBox {

    /**
     * Creates an empty extended text box.
     */
    public ExtendedTextBox() {
        super();

        // Catch the browser events.
        sinkEvents(Event.ONKEYUP);
        sinkEvents(Event.ONPASTE);

    }

    @Override
    public void onBrowserEvent(Event event) {
        super.onBrowserEvent(event);
        System.out.println(event.getTypeInt());

        switch (event.getTypeInt()) {
            case Event.ONKEYUP:
            case Event.ONPASTE: {
            // Fire the event after the text box shows the new data.
            Scheduler.get().scheduleDeferred(new ScheduledCommand() {

                @Override
                public void execute() {
                    fireEvent(new TextChangeEvent(ExtendedTextBox.this.getText()));
                }
            });
            break;
        }
        default:
        }
    }

    /**
     * Add a given {@link TextChangeEventHandler} to the widget.
     * 
     * @param handler
     *            the handler
     * @return {@link HandlerRegistration} used to remove the handler
     */
    public HandlerRegistration addTextChangeEventHandler(TextChangeEventHandler handler) {
        return addHandler(handler, TextChangeEvent.TYPE);
    }
}

A TextBox should fire a ChangeEvent (or ValueChangeEvent - don't know at the moment). TextBox应该触发一个ChangeEvent (或ValueChangeEvent目前尚不知道)。 So you could easily do something like this inside your constructor: 因此,您可以轻松地在构造函数中执行以下操作:

this.addChangeHandler(new ChangeHandler ...

If that's not enough, you could also listen to the Focus event. 如果这还不够,您还可以收听Focus事件。

Thanks for your help. 谢谢你的帮助。 I figured it out by myself today and it is quiet simple. 我今天自己弄清楚了,它很简单。 I didn't notice, that there is already the DropHandler . 我没有注意到,已经有了DropHandler

You can do this for example in the constructor: 例如,您可以在构造函数中执行此操作:

addDropHandler(new DropHandler() {

    @Override
    public void onDrop(DropEvent event) {
        if(!event.getDataTransfer().getData("text/plain").isEmpty()) {
            Scheduler.get().scheduleDeferred(new ScheduledCommand() {

                @Override
                public void execute() {
                    fireEvent(new TextChangeEvent(ExtendedTextBox.this.getText()));
                }
            });
        }

    }
});

To prevent the default behaviour of the TextField just add event.preventDefault(); 为了防止TextField的默认行为,只需添加event.preventDefault(); . Now you can get the input by calling event.getDataTransfer().getData("text/plain") and do your input validation etc. 现在,您可以通过调用event.getDataTransfer().getData("text/plain")进行输入,并进行输入验证等。

And as side effect the onBrowserEvent(Event event) method is called now by dropping something into the text field. 作为副作用,现在通过将某些内容放入文本字​​段来调用onBrowserEvent(Event event)方法。 But the type int is -1 , so it's not really helpful at this place. 但是int类型是-1 ,所以在这个地方并没有太大帮助。

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