RecyclerView粘性头部

已适配Androidx，需要切到androidx分支即可

一种新的解决思路，对比我之前写的PinnedSectionItemDecoration有如下好处：

• 粘性头部是放置在RecyclerView外面的View，对比之前绘制出来的粘性头部，能显示出点击的效果，并且处理点击事件更加简单

• 不需要频繁的创建粘性头部的View用于绘制，只需要刷新外置的粘性头部的数据即可

效果图

代码实现

StickyHeadContainer用来承载粘性头部布局，并且需要和RecyclerView的顶部对齐

<RelativeLayout
    android:id="@+id/content_main"
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="com.oubowu.stickydemo.MainActivity"
    tools:showIn="@layout/activity_main">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentTop="true"
        android:layout_margin="10dp"
        tools:background="@color/colorAccent"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true">

    </android.support.v7.widget.RecyclerView>

    <com.oubowu.stickyitemdecoration.StickyHeadContainer
        android:id="@+id/shc"
        android:layout_width="match_parent"
        android:layout_margin="10dp"
        android:layout_height="wrap_content">

        <include
            layout="@layout/item_stock_sticky_head"/>

    </com.oubowu.stickyitemdecoration.StickyHeadContainer>

</RelativeLayout>

RecyclerView只需要添加一个StickyItemDecoration即可实现粘性头部，需要传入StickyHeadContainer用于头部的处理，以及粘性头部的类型；然后头部的点击处理就像平常一样处理

        final StickyHeadContainer container = (StickyHeadContainer) findViewById(R.id.shc);
        final TextView tvStockName = (TextView) container.findViewById(R.id.tv_stock_name);
        final CheckBox checkBox = (CheckBox) container.findViewById(R.id.checkbox);
        final ImageView more = (ImageView) container.findViewById(R.id.iv_more);
        checkBox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                mAdapter.getData().get(mStickyPosition).getData().check = isChecked;
                mAdapter.notifyItemChanged(mStickyPosition);
            }
        });
        container.setDataCallback(new StickyHeadContainer.DataCallback() {
            @Override
            public void onDataChange(int pos) {
                mStickyPosition = pos;
                StockEntity.StockInfo item = mAdapter.getData().get(pos).getData();
                tvStockName.setText(item.stickyHeadName);
                checkBox.setChecked(item.check);
            }
        });
        more.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(MainActivity.this, "点击了粘性头部的更多", Toast.LENGTH_SHORT).show();
            }
        });
        container.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(MainActivity.this, "点击了粘性头部：" + tvStockName.getText(), Toast.LENGTH_SHORT).show();
            }
        });

        mRecyclerView = (RecyclerView) findViewById(R.id.recycler_view);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(MainActivity.this, LinearLayoutManager.VERTICAL, false));
        mRecyclerView.addItemDecoration(new StickyItemDecoration(container, RecyclerViewAdapter.TYPE_STICKY_HEAD));
        mRecyclerView.addItemDecoration(new SpaceItemDecoration(mRecyclerView.getContext()));

Adapter需要重写这两个方法，用于处理GridLayoutManager和StaggeredGridLayoutManager模式下的头部使之占满一行

    @Override
    public void onAttachedToRecyclerView(RecyclerView recyclerView) {
        super.onAttachedToRecyclerView(recyclerView);
        FullSpanUtil.onAttachedToRecyclerView(recyclerView, this, TYPE_STICKY_HEAD);
    }

    @Override
    public void onViewAttachedToWindow(RecyclerViewHolder holder) {
        super.onViewAttachedToWindow(holder);
        FullSpanUtil.onViewAttachedToWindow(holder, this, TYPE_STICKY_HEAD);
    }

PS:若是使用了下拉刷新的控件配合RecyclerView使用的话(显示刷新头部并且RecyclerView跟随头部的显示往下移动那种类型)，因为StickyHeadContainer是独立于RecyclerView存在的，不能跟随RecyclerView移动，需要根据刷新头部的显示情况设置StickyHeadContainer的可见性

License

Copyright 2016 oubowu

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.