Blackberry上实现文字滚动效果

最新推荐文章于 2025-09-06 10:38:25 发布

杨江

最新推荐文章于 2025-09-06 10:38:25 发布

阅读量2.5k

点赞数

分类专栏： BlackBerry Java 文章标签： blackberry null timer string scroll layout

BlackBerry Java 专栏收录该内容

107 篇文章

订阅专栏

本文介绍了一种在BlackBerry设备上实现滚动显示长文本的LabelField组件自定义方法。通过定时任务模拟文字滚动效果，并针对不同交互场景如聚焦、失焦等进行了优化。

博主doll还写了几篇BlackBerry开发的小文档，相当实用，感谢！

原文：

http://doll.javaeye.com/blog/569457

LabelField testLabel = new LabelField(
            "I swear to god up in the sky I will be your shelter when you cry Cause you are my everything.",
            Field.FOCUSABLE) {
        int currentChar = 0;
        String currentText = null;
        Font ourFont;
        private Timer _scrollTimer;
        private TimerTask _scrollTimerTask;

        protected void paint(Graphics graphics) {
            currentText = this.getText();
            if (currentChar < currentText.length()) {
                currentText = currentText.substring(currentChar);
            }
            graphics.drawText(currentText, 0, 0, DrawStyle.ELLIPSIS, Display
                    .getWidth());
        }

        protected void layout(int width, int height) {
            ourFont = this.getFont();
            setExtent(Display.getWidth(), ourFont.getHeight());
        }

        protected void onDisplay() {
            startScroll();
        }

        protected void onUnfocus() {
            startScroll();
        }

        private void startScroll() {
            // Start scrolling
            final String fullText = this.getText();
            if (_scrollTimer == null) {
                _scrollTimer = new Timer();
                _scrollTimerTask = new TimerTask() {
                    public void run() {
                        currentChar = currentChar + 4;
                        if (currentChar > fullText.length()) {
                            currentChar = 0;
                        }
                        invalidate();
                    }
                };
                _scrollTimer.scheduleAtFixedRate(_scrollTimerTask, 500, 500);
            }
        }

        protected void onFocus(int direction) {
            if (_scrollTimer != null) {
                _scrollTimerTask.cancel();
                _scrollTimer.cancel();
                _scrollTimer = null;
                _scrollTimerTask = null;
            }
        }

        protected boolean navigationMovement(int dx, int dy, int status,
                int time) {
            currentText = this.getText();
            int oldCurrentChar = currentChar;
            if (Math.abs(dx) > Math.abs(dy)) {
                // horizontal scroll
                if (dx > 0) {
                    currentChar = Math.min(currentText.length() - 1,
                            currentChar + 1);
                } else if (dx < 0) {
                    currentChar = Math.max(0, currentChar - 1);
                }
                if (oldCurrentChar != currentChar) {
                    this.invalidate();
                }
                return true;
            } else {
                return super.navigationMovement(dx, dy, status, time);
            }
        }
    };