今天在看第三方开源框架使用设计模式的相关书籍是，发现有一些第三方框架内部使用到了onAttachedToWindow来做了很多文章。本文我们一起了解一下，onAttachedToWindow调用的时机。

什么时候被调用的？

我们先看一下方法说明

    /     * This is called when the view is attached to a window.  At this point it     * has a Surface and will start drawing.  Note that this function is     * guaranteed to be called before {@link #onDraw(android.graphics.Canvas)},     * however it may be called any time before the first onDraw -- including     * before or after {@link #onMeasure(int, int)}.     *     * @see #onDetachedFromWindow()     */    @CallSuper    protected void onAttachedToWindow(