滑动底部工具条显示与隐藏

public class ScrollerBottomLayoutDelegation {

    private NestedScrollViewmNestedScroller;
    private ViewGroup mBottomLayout;

    private ScrollerBottomLayoutDelegation(NestedScrollView scroller, ViewGroup view){
        this.mNestedScroller = scroller;
        this.mBottomLayout = view;
        init();
    }

    /**
     * 开始初始化代理
    */
    private void init() {
        mNestedScroller.setOnScrollChangeListener(new NestedScrollView.OnScrollChangeListener() {
        	@Override
        	public void onScrollChange(NestedScrollView v, int scrollX, int scrollY, int oldScrollX, int oldScrollY) {
            		int dy = scrollY - oldScrollY;
                	// 第一次调用的时候   dy = nowYOffset
                	// 随后调用的时候可以做是变化量dy的叠加
                	// 在移动的过程中mBottomLayout.getTop()始终不会变
                	int nowYOffset = (int) (dy + mBottomLayout.getTranslationY());
                	Log.d("@@@", "dy = " + dy + " , nowYOffset = " + nowYOffset + " , top = " + mBottomLayout.getTop());
                	// scrollTo()，scrollBy()：移动view的显示位置，并不移动它的点击位置
                	// setTranslationX()：设置x轴平衡距离,将view的点击位置和显示位置同时移动
               	 	// 取消当前正在运行或者挂起的属性动画
                	ViewCompat.animate(mBottomLayout).cancel();
                	if (dy > 0) { // 手指向顶部移动  布局隐藏  
                    		if (nowYOffset < mBottomLayout.getHeight()) {
                        		mBottomLayout.setTranslationY(nowYOffset);
                    		} else {
                        		mBottomLayout.setTranslationY(mBottomLayout.getHeight());
                    		}
                	} else if (dy < 0) { // 手指向底部移动
                    		if (nowYOffset < 0) {
                       		mBottomLayout.setTranslationY(0);
                    	} else {
                        	mBottomLayout.setTranslationY(nowYOffset);
                    	}
                }
            }
        });

        mNestedScroller.setOnTouchListener(new View.OnTouchListener() {
        @Override
        public boolean onTouch(View v, MotionEvent event) {
            switch (event.getAction()) {
                case MotionEvent.ACTION_UP:
                case MotionEvent.ACTION_CANCEL:
                    // positive to check scrolling down  经测试：如果已经滑动到底部时再把手指往上滑回调该方法
                    if (!mNestedScroller.canScrollVertically(1)) {
                        animateHide();
                        return false;
                    }
                    // Negative to check scrolling up 经测试：如果已经滑动到顶部时再把手指往下滑回调该方法
                    if (!mNestedScroller.canScrollVertically(-1)) {
                            animateShow();
                            return false;
                    }
                    if (mNestedScroller.getScrollY() <= 0) return false;
                        if (mBottomLayout.getTranslationY() >= mBottomLayout.getHeight() / 2) {
                            // 手指向顶部滑动
                            animateHide();
                        } else {
                            animateShow();
                        }
                }
                return false;
            }
        });
    }

    public static void delegation(NestedScrollView scroller, ViewGroup view){
        new ScrollerBottomLayoutDelegation(scroller, view);
    }

    // y = top + translationY;
    private void animateShow(){
        mBottomLayout.animate()
                .translationY(0)
                .setInterpolator(new LinearInterpolator())
                .setDuration(180);
    }

    private void animateHide(){
        mBottomLayout.animate()
                .translationY(mBottomLayout.getHeight())
                .setInterpolator(new LinearInterpolator())
                .setDuration(180);
    }

}