获取控件的长宽

txtA.getViewTreeObserver().addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
            @Override
            public boolean onPreDraw() {
                int height = txtA.getMeasuredHeight();
                int width = txtA.getMeasuredWidth();
             txtA.getViewTreeObserver().removeOnPreDrawListener(this);
                return true;
            }
        });