View 1

App的跟节点是PhoneWindow$DecorView, DecorView是PhoneWindow下面的内部类实例。PhoneWindow$DecorView下面有三个child,分别是LinearLayout View@49da043和View@44ff410，一个表示 navigationBarBackground ,一个表示StatusBarBackground. Linearlayout下面有两个子child，分别是ViewStub实例和FrameLayout实例,FrameLayout有一个子类Fragment（这就是平常创建项目的inflate  xml最外层）什么所有的控件都是View的实例，onCreate() 中调用 setContentView(R.layout.main),Andorid就会从PhoneWindow 到每一层 执行 测量，布局，绘制。所有子类都 先执行 super.XXX方法几  1 

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);

2  布局   布局 会用到

@Overridepublic LayoutParams generateLayoutParams(AttributeSet attrs) {return new MarginLayoutParams(getContext(), attrs);}

自定义布局

@Overrideprotected void onLayout(boolean changed, int l, int t, int r, int b) {mListViews.clear();mHieghts.clear();//int lineWidth = 0;int lineHeight = 0;int width = getWidth();int count = getChildCount();List<View> mList = new ArrayList<>();for (int i = 0; i < count; i++) {View child = getChildAt(i);MarginLayoutParams mlp = (MarginLayoutParams) child.getLayoutParams();int childWidth = child.getMeasuredWidth() + mlp.leftMargin + mlp.rightMargin;int childHeight = child.getMeasuredHeight() + mlp.topMargin + mlp.bottomMargin;

3布局完了之后 就会绘图