如何使用相同的事件处理程序在GWT（或Java AWT Swing）中对同一类的多个对象执行相同的功能

Question

我刚刚开始研究Gwt2.0。我这里有两个文本框。两者都执行相同的事件操作。使用

addFocusListener()

我现在拥有的是。

areaBox.addFocusListener(new FocusListener(){

        @Override
        @Deprecated
        public void onFocus(Widget arg0) {
            // TODO Auto-generated method stub
            areaBox.setTitle("Area");
        }
            @Override
            public void onLostFocus(Widget arg0) {
                if(areaBox.getText().length() >= 4 )
                {
                    areaBox.setStyleName("gwt-TextBox-Success");
                }
                else
                {
                    areaBox.setStyleName("gwt-TextBox-Error");
                    cityBox.setText("Enter Area Name ");
                    areaBox.addFocusListener(new FocusListener(){

                        @Override
                        @Deprecated
                        public void onFocus(Widget arg0) {
                            areaBox.setText(null);
                            areaBox.setStyleName("gwt-TextBox-AE");

                        }

                        @Override
                        @Deprecated
                        public void onLostFocus(Widget arg0) {

                        }

                    });

                }
            }

});
cityBox.addFocusListener(new FocusListener(){

    @Override
    @Deprecated
    public void onFocus(Widget arg0) {
        cityBox.setTitle("City");
    }
        @Override
        public void onLostFocus(Widget arg0) {
            if(cityBox.getText().length() >= 4 )
            {
                cityBox.setStyleName("gwt-TextBox-Success");
            }
            else
            {
                cityBox.setStyleName("gwt-TextBox-Error");
                cityBox.setText("Enter City Name ");

                cityBox.addFocusListener(new FocusListener(){

                    @Override
                    @Deprecated
                    public void onFocus(Widget arg0) {
                        cityBox.setText(null);
                        cityBox.setStyleName("gwt-TextBox-AE");

                    }

                    @Override
                    @Deprecated
                    public void onLostFocus(Widget arg0) {
                        // TODO Auto-generated method stub

                    }

                });

            }
        }

}); 

代码的作用是什么。当聚焦于区域文本框时，会出现工具提示，显示要输入的内容。当Focus on它丢失或进入下一个文本框，例如City TextBox时，它会检查输入的字符串是否大于4个字符。如果是，则如果不应用ERROR css样式，则将SUCCESS css样式应用于该框。因此，当再次单击它（AreaBox）时，文本被清除并且css样式被重置。

以上是2个文本框之间的示例。 请帮帮我，我有近10个这样的字段，我想尽量减少代码。 我正在考虑使用集合或自定义小部件。但不知道从哪里开始。需要你的帮助和意见。感谢...

Answer 1

以下是我将如何解决这个问题：

areaBox.addFocusListener(generateFocusListener("Area", "Enter Area Name "));
cityBox.addFocusListener(generateFocusListener("City", "Enter City Name "));

FocusListener generateFocusListener(final String title, final String text) {
    return new FocusListener(){

            @Override
            @Deprecated
            public void onFocus(Widget widget) {
                // initial focus happens here
                TextBox box = (TextBox) widget;
                box.setTitle(title);
            }

            @Override
            public void onLostFocus(Widget widget) {
                // Focus is lost for the first time

                TextBox box = (TextBox) widget;
                if(box.getText().length() >= 4 )
                {
                    box.setStyleName("gwt-TextBox-Success");

                    // Change focus listener so that now once pressed it resets
                    box.addFocusListener(new FocusListener(){

                        @Override
                        @Deprecated
                        public void onFocus(Widget widget) {
                            TextBox box = (TextBox) widget;
                            box.setText(null);
                            box.setStyleName("gwt-TextBox-AE");
                        }

                        @Override
                        @Deprecated
                        public void onLostFocus(Widget widget) {
                            TextBox box = (TextBox) widget;
                            if(box.getText().length() >= 4 )
                            {
                                box.setStyleName("gwt-TextBox-Success");
                            }
                            else
                            {
                                box.setStyleName("gwt-TextBox-Error");
                                box.setText(text);
                            }

                        }

                    });
                }
                else
                {
                    box.setStyleName("gwt-TextBox-Error");
                    box.setText(text);
                }
            }

    };
}