仿二手车汽车之家折叠列表效果

public class ViewDropList extends FrameLayout {
    private ViewDragHelper dragHelper;
    private View listView;
    private boolean mMenuIsOpen = false;
    //头部高度
    private int headerHeight;

    public ViewDropList(Context context) {
        this(context, null);
    }

    public ViewDropList(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public ViewDropList(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        dragHelper = ViewDragHelper.create(this, callback);
    }

    private ViewDragHelper.Callback callback = new ViewDragHelper.Callback() {
        @Override
        public boolean tryCaptureView(View child, int pointerId) {
            //在这个方法中可以指定哪个字view可以拖动，返回true代表全部子view可以拖动
            return listView == child;
        }

        @Override
        public int clampViewPositionVertical(View child, int top, int dy) {
            //垂直拖动的时候回调
            //设定拖动范围
            if (top <= 0) {
                top = 0;
            }
            if (top >= headerHeight) {
                top = headerHeight;
            }
            return top;
        }

        @Override
        public int clampViewPositionHorizontal(View child, int left, int dx) {
            //横向拖动的时候回调  将值改为return left
            return super.clampViewPositionHorizontal(child, left, dx);
        }

        @Override
        public void onViewReleased(View releasedChild, float xvel, float yvel) {
            super.onViewReleased(releasedChild, xvel, yvel);
            //拖动松手的时候会回调
            if (listView == releasedChild) {
                int listViewTop = listView.getTop();
                if (listViewTop > headerHeight / 2) {
                    //滚动打开
                    dragHelper.settleCapturedViewAt(0, headerHeight);
                    mMenuIsOpen = true;
                } else {
                    //滚动关闭
                    dragHelper.settleCapturedViewAt(0, 0);
                    mMenuIsOpen = false;
                }
                invalidate();
            }
        }
    };
    private float downY;

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
//        //判断是否打开，打开的话直接将事件拦截掉
//        if(mMenuIsOpen){
//            // 向下滑动 && 滚动到了顶部，拦截不让ListView做处理
//            return true;
//        }
        switch (ev.getAction()) {
            case MotionEvent.ACTION_DOWN:
                //按下的时候记录下按下坐标
                downY = ev.getY();
                dragHelper.processTouchEvent(ev);
                break;
            case MotionEvent.ACTION_MOVE:
                //获取移动是的坐标
                float evY = ev.getY();
                if (evY - downY > 0 && !canChildScrollUp()) {
                    // 向下滑动 && 滚动到了顶部，拦截不让ListView做处理
                    return true;
                } else {
                    if (listView instanceof RecyclerView) {
                        //如果是打开请recycleview已经滚动到最底部了，将事件拦截掉
                        if (mMenuIsOpen && isVisBottom((RecyclerView) listView)) {
                            return true;
                        }
                    }
                }
                break;
        }
        return super.onInterceptTouchEvent(ev);
    }

    /**
     * 判断recycleview是否滚动到底部
     * @param recyclerView
     * @return
     */
    private boolean isVisBottom(RecyclerView recyclerView) {
        LinearLayoutManager layoutManager = (LinearLayoutManager) recyclerView.getLayoutManager();
        //屏幕中最后一个可见子项的position
        int lastVisibleItemPosition = layoutManager.findLastVisibleItemPosition();
        //当前屏幕所看到的子项个数
        int visibleItemCount = layoutManager.getChildCount();
        //当前RecyclerView的所有子项个数
        int totalItemCount = layoutManager.getItemCount();
        //RecyclerView的滑动状态
        int state = recyclerView.getScrollState();
        if (visibleItemCount > 0 && lastVisibleItemPosition == totalItemCount - 1 && state == recyclerView.SCROLL_STATE_IDLE) {
            return true;
        } else {
            return false;
        }
    }

    /**
     * @return Whether it is possible for the child view of this layout to
     * scroll up. Override this if the child view is a custom view.
     * 判断View是否滚动到了最顶部,还能不能向上滚
     */
    public boolean canChildScrollUp() {
        if (android.os.Build.VERSION.SDK_INT < 14) {
            if (listView instanceof AbsListView) {
                final AbsListView absListView = (AbsListView) listView;
                return absListView.getChildCount() > 0
                        && (absListView.getFirstVisiblePosition() > 0 || absListView.getChildAt(0)
                        .getTop() < absListView.getPaddingTop());
            } else {
                return ViewCompat.canScrollVertically(listView, -1) || listView.getScrollY() > 0;
            }
        } else {
            return ViewCompat.canScrollVertically(listView, -1);
        }
    }

    @Override
    public void computeScroll() {
        super.computeScroll();
        if (dragHelper.continueSettling(true)) {
            invalidate();
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        dragHelper.processTouchEvent(event);
        return true;
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        View childAt = getChildAt(0);
        headerHeight = childAt.getMeasuredHeight();
    }

    @Override
    protected void onFinishInflate() {
        super.onFinishInflate();
        //该方法在加载完布局会调用
        //获取子view
        int childCount = getChildCount();
        if (childCount != 2) {
            return;
        }
        //获取列表view
        listView = getChildAt(1);
    }
}

<?xml version="1.0" encoding="utf-8"?>
<com.lsm.view_day14.ViewDropList xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.lsm.view_day14.MainActivity">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="200dp"
        android:text="头部内容"
        android:background="@color/colorAccent"/>
    <android.support.v7.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@android:color/white"/>
</com.lsm.view_day14.ViewDropList>

public class MainActivity extends AppCompatActivity {
    private RecyclerView recyclerView;
    private List<String> list=new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        for(int i=0;i<20;i++){
            list.add("item"+i);
        }
        recyclerView= (RecyclerView) findViewById(R.id.recycler_view);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        DropListAdapter adapter=new DropListAdapter();
        recyclerView.setAdapter(adapter);
    }
    class DropListAdapter extends RecyclerView.Adapter<DropListAdapter.DropHolder>{

        @Override
        public DropHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            View view = LayoutInflater.from(MainActivity.this).inflate(R.layout.item_layout, parent, false);
            DropHolder holder=new DropHolder(view);
            return holder;
        }

        @Override
        public void onBindViewHolder(DropHolder holder, int position) {
            final String txt = list.get(position);
            holder.tvItem.setText(txt);
            holder.tvItem.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Toast.makeText(MainActivity.this,txt,Toast.LENGTH_LONG).show();
                }
            });
        }

        @Override
        public int getItemCount() {
            return list.size();
        }

        class DropHolder extends RecyclerView.ViewHolder{
            public TextView tvItem;
            public DropHolder(View itemView) {
                super(itemView);
                tvItem= (TextView) itemView.findViewById(R.id.tv_item);
            }
        }
    }
}