java - 在 GWT 中取消按键事件

Question

我想取消长文本框的按键事件，以便用户新按下的字符不会输入到文本框中

longBox_1.addKeyPressHandler(new KeyPressHandler(){
    @Override
    public void onKeyPress(KeyPressEvent event) {
        String Valid="1234567890";
        if (!Valid.contains(String.valueOf(event.getCharCode()))) {
            // the code to cancel the event to be placed here
        }
    }
});

Answer 1

如果您的 longBox_1 是您的类的私有(private)成员或最终变量，则取消事件的代码是:

longBox_1.cancelKey();

否则，如果您确定事件源对应于 TextBox，则可以转换事件源:

((TextBox)event.getSource()).cancelKey();

这是 cancelKey 的文档:

If a keyboard event is currently being handled on this text box, calling this method will suppress it. This allows listeners to easily filter keyboard input