public class CoordinatorLayout extends ViewGroup implements NestedScrollingParent2

建立依賴

onMeasure-》prepareChildren-》dependsOn-》layoutDependsOn
測量的第一步就是確定依賴關系
prepareChildren中getResolvedLayoutParams找到支持behavior的節(jié)點，然后找出互相依賴關系（2個for掃描所有節(jié)點，兩兩對比），結果加入緩存列表
layoutDependsOn被子類覆蓋，只需要對dependency判斷返回成功，就建立依賴

視圖改變

onNestedScroll-》onChildViewsChanged-》onDependentViewChanged

child的ontouch事件里有對parent的調用

behavior實例化parseBehavior內，ThreadLocal<Map<String, Constructor<Behavior>>>存放構造函數(shù)，用反射獲取構造緩存

補充androidx.core.util.Pools

private final Object[] mPool;//默認的存儲數(shù)組
private int mPoolSize;//當前剩余容量計數(shù)器

public T acquire() {
            if (mPoolSize > 0) {
                final int lastPooledIndex = mPoolSize - 1;
                T instance = (T) mPool[lastPooledIndex];
                mPool[lastPooledIndex] = null;
                mPoolSize--;
                return instance;
            }
            return null;
        }
private static Rect acquireTempRect() {
        Rect rect = sRectPool.acquire();
        if (rect == null) {
            rect = new Rect();
        }
        return rect;
    }
 public boolean release(@NonNull T instance) {
            if (isInPool(instance)) {
                throw new IllegalStateException("Already in the pool!");
            }
            if (mPoolSize < mPool.length) {
                mPool[mPoolSize] = instance;
                mPoolSize++;
                return true;
            }
            return false;
        }

        private boolean isInPool(@NonNull T instance) {
            for (int i = 0; i < mPoolSize; i++) {
                if (mPool[i] == instance) {
                    return true;
                }
            }
            return false;
        }
private static void releaseTempRect(@NonNull Rect rect) {
        rect.setEmpty();
        sRectPool.release(rect);
    }

總是從末尾獲得引用，引用賦值后使用，釋放時清空rect的值，但是存入到數(shù)組內，不釋放引用，這樣就是緩存了新建過程。