User interface 如何动态更改blackberry标签字段的字体颜色？

我有一个标签字段和三个按钮，分别是红色、黄色和蓝色。如果单击红色按钮，则标签字段字体颜色应更改为红色；类似地，如果我单击黄色按钮，则字体颜色应更改为黄色；同样，根据按钮颜色，标签字段中的字体颜色也应改变

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有人能告诉我怎么做吗？

通过在super.paint之前设置graphics.setColor on paint事件，可以轻松维护LabelField中的字体颜色：

    class FCLabelField extends LabelField {
        public FCLabelField(Object text, long style) {
            super(text, style);
        }

        private int mFontColor = -1;

        public void setFontColor(int fontColor) {
            mFontColor = fontColor;
        }

        protected void paint(Graphics graphics) {
            if (-1 != mFontColor)
                graphics.setColor(mFontColor);
            super.paint(graphics);
        }
    }

    class Scr extends MainScreen implements FieldChangeListener {
        FCLabelField mLabel;
        ButtonField mRedButton;
        ButtonField mGreenButton;
        ButtonField mBlueButton;

        public Scr() {
            mLabel = new FCLabelField("COLOR LABEL", 
                    FIELD_HCENTER);
            add(mLabel);
            mRedButton = new ButtonField("RED", 
                    ButtonField.CONSUME_CLICK|FIELD_HCENTER);
            mRedButton.setChangeListener(this);
            add(mRedButton);
            mGreenButton = new ButtonField("GREEN", 
                    ButtonField.CONSUME_CLICK|FIELD_HCENTER);
            mGreenButton.setChangeListener(this);
            add(mGreenButton);
            mBlueButton = new ButtonField("BLUE", 
                    ButtonField.CONSUME_CLICK|FIELD_HCENTER);
            mBlueButton.setChangeListener(this);
            add(mBlueButton);
        }

        public void fieldChanged(Field field, int context) {
            if (field == mRedButton) {
                mLabel.setFontColor(Color.RED);
            } else if (field == mGreenButton) {
                mLabel.setFontColor(Color.GREEN);
            } else if (field == mBlueButton) {
                mLabel.setFontColor(Color.BLUE);
            }
            invalidate();
        }
    }