RecyclerView和列表

冷不防 2022-05-29 08:40 216阅读 0赞

转载请注明链接：[http://blog.csdn.net/feather\_wch/article/details/79630459][http_blog.csdn.net_feather_wch_article_details_79630459]

总结列表和RecylerView的要点。  
1. ListView的简略介绍，市面上资料很多  
2. RecyclerView给出最基本的步骤，和最简单的实现方法。

# 列表和RecyclerView #

版本:2018/3/28-1(22:10)

*  列表和RecyclerView
    
     *  ListView
     *  RecyclerView
        
         *  分割线定制：ItemDecoration
         *  拖拽和滑动删除
     *  参考资料

## ListView ##

比较简单，四步骤：  
1. ListView所在的布局和Item的布局  
2. 自定义适配器(继承BaseAdapter)  
3. 给ListView设置适配器对象

自定义适配器主要四部分工作：  
1. getCount()-返回数据集的总数，如List的size等  
2. getItem(position)-返回数据集中position位置的数据  
3. getItemId(int position)-return position即可  
4. getView()-通过Item的布局去自定义每行的效果

convertView+ViewHolder是重写getView()的最好办法，能减少`findViewById`的次数，也减少了`重绘View`

## RecyclerView ##

1、RecyclerView的特点

> 1.  名称`回收循环视图`—只管回收与复用View
> 2.  强制使用`ViewHolder`，并将其封装，该控件会自动回收和复用

2、RecyclerView的优点

> 1.  `Item`复用性高
> 2.  `灵活、可定制化高、可扩展性高`\-提供插拔式体验；高度解耦；
> 3.  可控制`显示的方式`\-通过布局管理器`LayoutManager`
> 4.  可控制`Item间的间隔(可绘制)`\-通过`ItemDecoration`
> 5.  可控制`Item的增删动画`\-通过`ItemAnimator`

3、RecyclerView的缺点

> 实现`控制点击`、`长按事件`比较麻烦(要自己写)

4、RecyclerView的实现步骤

> 1.  定义包含`RecyclerView`的布局
> 2.  实现`RecyclerView`的`Item布局`
> 3.  继承并实现`RecyclerView.Adapter`(ViewHolder的实现，`点击事件`的实现，定义`列表等数据结构`用于存储数据)
> 4.  给`RecyclerView`设置`Adapter`, 并且设置监听器

5、RecyclerView的最简单实现

> 1-Activity的布局和`Item`的布局

//activity_recler_view.XMML
    <android.support.constraint.ConstraintLayout ...>
    
        <android.support.v7.widget.RecyclerView android:id="@+id/activity_recler_view" android:layout_width="match_parent" android:layout_height="match_parent">
    
        </android.support.v7.widget.RecyclerView>
    
    </android.support.constraint.ConstraintLayout>

//reclerview_item.xml
    <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="vertical">
    
        <TextView android:id="@+id/item_text" android:layout_width="match_parent" android:layout_height="50dp" android:gravity="center" android:text="TextView" android:textColor="@color/colorAccent" android:textSize="20dp" />
    
    </LinearLayout>

> 2-自定义Adapter

public class RecyclerViewAdapter extends RecyclerView.Adapter{ 
        //1. 布局
        private LayoutInflater mInflater;
        //2. 数据
        private ArrayList<String> mDatas;
        public RecyclerViewAdapter(Context context, ArrayList<String> stringArrayList){
            super();
            mInflater = LayoutInflater.from(context);
            mDatas = stringArrayList;
        }
        //3. 自定义ViewHolder
        class ViewHolder extends RecyclerView.ViewHolder{
            private TextView name;
    
            public ViewHolder(View itemView) {
                super(itemView);
                name = itemView.findViewById(R.id.item_text);
                itemView.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        if(mItemClickListener != null){
                            mItemClickListener.onItemClick(v, getPosition());
                        }
                    }
                });
            }
    
            public TextView getName(){
                return name;
            }
        }
    
        //4. 通过Item的布局创建ViewHolder
        @Override
        public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            return new ViewHolder(mInflater.inflate(R.layout.reclerview_item, parent, false)));
        }
        //5. 完成类似于getView里面显示数据的功能
        @Override
        public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
            ViewHolder viewHolder = (ViewHolder) holder;
            viewHolder.name.setText(mDatas.get(position));
        }
        //6. 获取数据size
        @Override
        public int getItemCount() {
            return mDatas.size();
        }
    
        //7. 点击事件的监听
        private ItemClickListener mItemClickListener;
        public interface ItemClickListener{ 
            public void onItemClick(View view, int position);
        }
        public void setOnItemClickListener(ItemClickListener listener){
            mItemClickListener = listener;
        }
    }

> 3-Activity.java

public class ReclerViewActivity extends Activity { 
    
        RecyclerView mRecyclerView;
        RecyclerViewAdapter mRecyclerViewAdapter;
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_recler_view);
            mRecyclerView = findViewById(R.id.activity_recler_view);
    
            ArrayList<String> arrayList = new ArrayList<>();
            arrayList.add("Wang");
            arrayList.add("Gu");
            arrayList.add("Li");
            arrayList.add("Wen");
    
            //1. 布局
            LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
            mRecyclerView.setLayoutManager(linearLayoutManager);
            //2. 适配器
            mRecyclerViewAdapter = new RecyclerViewAdapter(this, arrayList);
            mRecyclerViewAdapter.setOnItemClickListener(new RecyclerViewAdapter.ItemClickListener() {
                @Override
                public void onItemClick(View view, int position) {
                    Toast.makeText(ReclerViewActivity.this, "onItemClick position=" + position, Toast.LENGTH_SHORT).show();
                }
            });
            mRecyclerView.setAdapter(mRecyclerViewAdapter);
        }
    }

6、RecyclerView的基本使用

mRecyclerView = findView(R.id.id_recyclerview);
    //1. 设置布局管理器
    mRecyclerView.setLayoutManager(layout);
    //2. 设置adapter
    mRecyclerView.setAdapter(adapter)
    //3. 设置Item增加、移除动画
    mRecyclerView.setItemAnimator(new DefaultItemAnimator());
    //4. 添加分割线
    mRecyclerView.addItemDecoration(new DividerItemDecoration(getActivity(), DividerItemDecoration.HORIZONTAL_LIST));

### 分割线定制：ItemDecoration ###

7、ItemDecoration的使用和主要方法的要点(可以参考官方提供的`DividerItemDecoration`的内部实现)

> 1.  `ItemDecoration`是抽象类
> 2.  使用方法；`mRecyclerView.addItemDecoration()`
> 3.  四个方法：`onDraw()\onDrawOver()\getItemOffsets\getItemOffsets`
> 4.  `addItemDecoration()`后，绘制顺序`onDraw()->onDrawOver()`\-复写其中一个即可。
> 5.  `getItemOffsets` 可以通过`outRect.set()`为每个Item设置一定的偏移量，主要用于`绘制Decorator`。

mRecyclerView = findViewById(R.id.activity_imageview_recyclerview);
    mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
    mRecyclerView.setAdapter(mRVAdapter = new RVAdapter(this, cityNames));
    //1. 这里设置分割线
    mRecyclerView.addItemDecoration(new DividerItemDecoration(this, DividerItemDecoration.VERTICAL));

8、LayoutManager的布局管理器

### 拖拽和滑动删除 ###

9、RecyclerView的拖拽和滑动删除如何实现？

> 1.  都是通过`ItemTouchHelper`实现
> 2.  拖拽与滑动需要在`getMovementFlags`中进行开关
> 3.  拖拽的实现在`onMove()`中完成
> 4.  滑动删除是在`onSwiped()`中实现

//1. 帮助快速处理拖拽和滑动删除的类
            ItemTouchHelper itemTouchHelper = new ItemTouchHelper(new ItemTouchHelper.Callback() {
                /**==================================== * 2、通过返回值设置是否处理拖拽或者滑动事件 *=======================================*/
                @Override
                public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
                    if(recyclerView.getLayoutManager() instanceof GridLayoutManager){
                        //1. Grid布局中上下左右都可以拖拽
                        int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN
                                | ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT;
                        int swipeFlags = 0;
                        return makeMovementFlags(dragFlags, swipeFlags);
                    }else{
                        //2. 列表只有UP/DOWN两种方式
                        int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN;
                        //3. 滑动删除只有两个方向
                        int swipeFlags = ItemTouchHelper.START | ItemTouchHelper.END;
                        return makeMovementFlags(dragFlags, swipeFlags);
                    }
                }
                /**==================================== * 3、在拖拽过程中会不断回调 *=======================================*/
                @Override
                public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
                    //1. 获取到当前Item和目标Item的下标
                    int fromPosition = viewHolder.getAdapterPosition();
                    int toPosition = target.getAdapterPosition();
                    if(fromPosition < toPosition){
                        for(int i = fromPosition; i < toPosition; i++){
                            Collections.swap(mAdapter.getDatas(), i, i + 1);
                        }
                    }else{
                        for(int i = fromPosition; i > toPosition; i--){
                            Collections.swap(mAdapter.getDatas(), i, i - 1);
                        }
                    }
                    mAdapter.notifyItemMoved(fromPosition, toPosition);
                    return true;
                }
    
                //长按Item开始拖拽的时候调用
                @Override
                public void onSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionState) {
                    //设置为灰色
                    if(actionState != ItemTouchHelper.ACTION_STATE_IDLE){
                        viewHolder.itemView.setBackgroundColor(Color.LTGRAY);
                    }
                    super.onSelectedChanged(viewHolder, actionState);
                }
                //拖拽结束松开手指的时候调用
                @Override
                public void clearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
                    super.clearView(recyclerView, viewHolder);
                    viewHolder.itemView.setBackgroundColor(Color.WHITE);
                }
    
                /**============================== * 滑动删除的回调 *==========================*/
                @Override
                public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
                    //彻底删除目标Item
                    int targetPostion = viewHolder.getAdapterPosition();
                    mAdapter.notifyItemRemoved(targetPostion);
                    mAdapter.getDatas().remove(targetPostion);
                }
            });
            itemTouchHelper.attachToRecyclerView(mRecyclerView);

10、RecyclerView如何自定义ItemView的拖拽效果(如第一个Item禁止拖拽)？

> 1.需要在`ItemTouchHelper`中的`isLongPressDragEnabled()`禁止有所Item的拖拽

/** * 默认禁止所有Item的拖拽，并给RecyclerView设置长按监听事件，并进行处理 */
    @Override
    public boolean isLongPressDragEnabled() {
          return false;
    }

> 2.给RecyclerView设置`ItemTouchListener(本质通过手势探测器GestureDetectorCompat完成)`\-在长按事件中用`ItemTouchHelper`的`startDrag`方法进行拖拽

mRecyclerView.addOnItemTouchListener(new OnRecyclerItemClickListener(mRecyclerView) {
                @Override
                public void onItemClick(RecyclerView.ViewHolder viewHolder) {
                    //TODO 点击事件
                }
    
                @Override
                public void onLongClick(RecyclerView.ViewHolder viewHolder) {
                    if(viewHolder.getLayoutPosition() != 0){
                        itemTouchHelper.startDrag(viewHolder);
                    }
                }
            });

> 3-Item点击事件监听器的具体实现：

public abstract class OnRecyclerItemClickListener implements RecyclerView.OnItemTouchListener{ 
        private RecyclerView mRecyclerView;
        private GestureDetectorCompat mGestureDetectorCompat; //手势探测器
    
        public OnRecyclerItemClickListener(RecyclerView recyclerView){
            mRecyclerView = recyclerView;
            //手势探测器
            mGestureDetectorCompat = new GestureDetectorCompat(mRecyclerView.getContext(), new GestureDetector.SimpleOnGestureListener(){
                //1. 普通点击操作
                @Override
                public boolean onSingleTapUp(MotionEvent e) {
                    View curItemView = mRecyclerView.findChildViewUnder(e.getX(), e.getY());
                    if(curItemView != null){
                        RecyclerView.ViewHolder viewHolder = mRecyclerView.getChildViewHolder(curItemView);
                        onItemClick(viewHolder);
                    }
                    return true;
                }
                //2. 长按操作
                @Override
                public void onLongPress(MotionEvent e) {
                    View curItemView = mRecyclerView.findChildViewUnder(e.getX(), e.getY());
                    if(curItemView != null){
                        RecyclerView.ViewHolder viewHolder = mRecyclerView.getChildViewHolder(curItemView);
                        onLongClick(viewHolder);
                    }
                }
            });
        }
    
        @Override
        public boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent e) {
            return mGestureDetectorCompat.onTouchEvent(e);
        }
    
        @Override
        public void onTouchEvent(RecyclerView rv, MotionEvent e) {
            mGestureDetectorCompat.onTouchEvent(e);
        }
    
        @Override
        public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {
        }
    
        public abstract void onItemClick(RecyclerView.ViewHolder viewHolder);
        public abstract void onLongClick(RecyclerView.ViewHolder viewHolder);
    }

## 参考资料 ##

1.  [ Android RecyclerView 使用完全解析][Android RecyclerView]
2.  [clipToPadding解决列表滚动无法触及到Padding的问题][clipToPadding_Padding]
3.  [用RecyclerView做一个小清新的Gallery效果][RecyclerView_Gallery]
4.  [RecyclerView 梳理：点击&长按事件、分割线、拖曳排序、滑动删除][RecyclerView]
5.  [【wanandroid】RecyclerView资料列表][wanandroid_RecyclerView]
6.  [RecyclerView进阶(一)RecyclerView实现双列表联动][RecyclerView_RecyclerView]

[http_blog.csdn.net_feather_wch_article_details_79630459]: http://blog.csdn.net/feather_wch/article/details/79630459
[Android RecyclerView]: https://blog.csdn.net/lmj623565791/article/details/45059587
[clipToPadding_Padding]: https://blog.csdn.net/litefish/article/details/52471273
[RecyclerView_Gallery]: https://juejin.im/post/5a30fe5a6fb9a045132ab1bf
[RecyclerView]: https://blog.csdn.net/shedoor/article/details/77326167
[wanandroid_RecyclerView]: http://www.wanandroid.com/article/query?k=recyclerview
[RecyclerView_RecyclerView]: https://www.jianshu.com/p/5864db231ed5