解决方法：
在TextField源码上 加上editString();函数：
public void pointerReleased(int x, int y) {
        // unlike text area the text field supports shifting the cursor with the touch screen
     editString();
        String text = getText();
        int textLength = text.length();
        int position = 0;
        Font f = getStyle().getFont();
        x -= getAbsoluteX();
        for(int iter = 0 ; iter < textLength ; iter++) {
            int width = f.substringWidth(text, 0, iter);
            if(x > width) {
                position = iter;
            } else {
                break;
            }
        }
        if(position == textLength - 1) {
            if(f.stringWidth(text) < x) {
                position = textLength;
            }
        }
        setCursorPosition(position);
        repaint();
    }

或者官方的解决方法：http://forums.java.net/jive/thread.jspa?threadID=52716