android的view的生命周期

总：android的view类是android的布局，组件的父类，了解view的生命周期，对于布局，组件的使用，以及自定义组件的构造将会有更好的了解。

（1）onAttachToWindow（onAttachedToWindow运行在onResume之后）

     

     * 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)}.

（2）onMeasure（当控件的父元素正要放置该控件时调用.父元素会问子控件一个问题，“你想要用多大地方啊？”，然后传入两个参数——widthMeasureSpec和heightMeasureSpec）.

     * Measure the view and its content to determine the measured width and the
     * measured height. This method is invoked by {@link #measure(int, int)} and
     * should be overriden by subclasses to provide accurate and efficient
     * measurement of their contents.

（3）onSizeChanged

      （1）会被View.java的方法private void sizeChange(int newWidth, int newHeight, int oldWidth, int oldHeight)调用

      （2）sizeChange会被View.java的方法setTop(int top)、setFrame(int left, int top, int right, int bottom)、setRight(int right）、setLeft(int left)、setBottom(int bottom)调用

     * This is called during layout when the size of this view has changed. If
     * you were just added to the view hierarchy, you're called with the old
     * values of 0.

（4）onLayout

       （1）是第二阶段的布局机制 （第一阶段是测量）

       （2）通过第一阶段获得的测量值，布置子元素的位置

     * In this phase, each parent calls
     * layout on all of its children to position them.
     * This is typically done using the child measurements
     * that were stored in the measure pass()

（7）onDraw

    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
    }

     * Called from layout when this view should
     * assign a size and position to each of its children.
     *
     * Derived classes with children should override
     * this method and call layout on each of
     * their children.
     * @param changed This is a new size or position for this view
     * @param left Left position, relative to parent
     * @param top Top position, relative to parent
     * @param right Right position, relative to parent
     * @param bottom Bottom position, relative to parent

（8）onDetachedFromWindow

   * This is called when the view is detached from a window.  At this point it
     * no longer has a surface for drawing.
     *