Android RecyclerView的使用（二）——添加分割线

桃扇骨 2022-06-04 08:26 502阅读 0赞

## Android RecyclerView的使用（二）——添加分割线 ##

**前言：** RecyclerView提供了一种插拔式的体验，高度的解耦，异常的灵活，通过设置它提供的不同LayoutManager，ItemDecoration , ItemAnimator实现绚丽的效果。

*  通过布局管理器LayoutManager，可以控制其显示的方式；
 *  通过ItemDecoration，可以控制Item间的间隔（可定制）；
 *  通过ItemAnimator，可以控制Item增删的动画；
 *  至于点击、长按事件，RecyclerView并没有给我们提供相应的方法接口，需要我们自己实现。

上一节我们了解了RecyclerView的基本使用，这节我们将介绍如何为RecyclerView **添加分割线**。

**效果图：**

![这里写图片描述][SouthEast]

第一步：activity\_main.xml布局文件

<?xml version="1.0" encoding="utf-8"?>
    <android.support.constraint.ConstraintLayout 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">
    
        <android.support.v7.widget.RecyclerView
            android:id="@+id/recyclerView"
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>
    
    </android.support.constraint.ConstraintLayout>

第二步：定义item的样式，item\_single\_textview.xml

<?xml version="1.0" encoding="utf-8"?>
    <LinearLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:background="#442F2F2F"
        android:layout_height="72dp">
    
        <ImageView
            android:id="@+id/imageView"
            android:layout_margin="20dp"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />
    
        <TextView
            android:id="@+id/textView"
            android:layout_gravity="center_vertical"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />
    
    </LinearLayout>

第三步：自定义Adapter适配器

public class MyAdapter extends RecyclerView.Adapter<MyViewHolder> {
        
    
        private LayoutInflater mInflater;
        private Context mContext;
        private List<String> mDatas;
        private int[] imgIds;
    
        public MyAdapter(Context context, List<String> datas, int[] imgIds) {
            this.mContext = context;
            this.mDatas = datas;
            this.imgIds = imgIds;
            mInflater = LayoutInflater.from(context);
        }
    
        @Override
        public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            View view = mInflater.inflate(R.layout.item_single_textview, parent, false);
            MyViewHolder viewHolder = new MyViewHolder(view);
            return viewHolder;
        }
    
        @Override
        public void onBindViewHolder(MyViewHolder holder, int position) {
            holder.textView.setText(mDatas.get(position));
            holder.imageView.setBackgroundResource(imgIds[ position % 7]);
        }
    
        @Override
        public int getItemCount() {
            return mDatas.size();
        }
    }
    class MyViewHolder extends RecyclerView.ViewHolder {
        
    
        ImageView imageView;
        TextView textView;
    
        public MyViewHolder(View itemView) {
            super(itemView);
            textView = itemView.findViewById(R.id.textView);
            imageView = itemView.findViewById(R.id.imageView);
        }
    }

第四步：自定义分割线类（说明，我所使用的分割线类是从网上找的，不是本人实现的）

public class DividerItemDecoration extends RecyclerView.ItemDecoration {
        
    
        public static final int HORIZONTAL_LIST = LinearLayoutManager.HORIZONTAL;
        public static final int VERTICAL_LIST = LinearLayoutManager.VERTICAL;
        private static final int[] ATTRS = new int[]{android.R.attr.listDivider};
        private Drawable mDivider;
    
        private int mOrientation;
    
        public DividerItemDecoration(Context context, int orientation) {
            final TypedArray a = context.obtainStyledAttributes(ATTRS);
            mDivider = a.getDrawable(0);
            a.recycle();
            setOrientation(orientation);
        }
    
        public void setOrientation(int orientation) {
            if (orientation != HORIZONTAL_LIST && orientation != VERTICAL_LIST) {
                throw new IllegalArgumentException("invalid orientation");
            }
            mOrientation = orientation;
        }
    
        @Override
        public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
            super.onDraw(c, parent, state);
            if (mOrientation == VERTICAL_LIST) {
                drawVertical(c, parent);
            } else {
                drawHorizontal(c, parent);
            }
        }
    
        public void drawVertical(Canvas c, RecyclerView parent) {
            final int left = parent.getPaddingLeft();
            final int right = parent.getWidth() - parent.getPaddingRight();
    
            final int childCount = parent.getChildCount();
    
            for (int i = 0; i < childCount; i++) {
                final View child = parent.getChildAt(i);
                RecyclerView v = new RecyclerView(
                        parent.getContext());
                final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
                        .getLayoutParams();
                final int top = child.getBottom() + params.bottomMargin;
                final int bottom = top + mDivider.getIntrinsicHeight();
                mDivider.setBounds(left, top, right, bottom);
                mDivider.draw(c);
            }
        }
    
        public void drawHorizontal(Canvas c, RecyclerView parent) {
            final int top = parent.getPaddingTop();
            final int bottom = parent.getHeight() - parent.getPaddingBottom();
    
            final int childCount = parent.getChildCount();
            for (int i = 0; i < childCount; i++) {
                final View child = parent.getChildAt(i);
                final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
                        .getLayoutParams();
                final int left = child.getRight() + params.rightMargin;
                final int right = left + mDivider.getIntrinsicHeight();
                mDivider.setBounds(left, top, right, bottom);
                mDivider.draw(c);
            }
        }
    
        @Override
        public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
            super.getItemOffsets(outRect, view, parent, state);
            if (mOrientation == VERTICAL_LIST) {
                outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());
            } else {
                outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);
            }
        }
    
    }

第五步：MainActivity.java

public class MainActivity extends AppCompatActivity {
    
        private RecyclerView recyclerView;
    
        private List<String> mDatas;
        private int[] imgIds;
        private MyAdapter mAdapter;
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            initDatas();
    
            recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
    
            mAdapter = new MyAdapter(this, mDatas, imgIds);
            recyclerView.setAdapter(mAdapter);
    
            //设置RecyclerView的布局管理
            LinearLayoutManager manager = new LinearLayoutManager(this,
                    LinearLayoutManager.VERTICAL, false);
            recyclerView.setLayoutManager(manager);
    
            //设置RecyclerView的item间分割线
            recyclerView.addItemDecoration(new DividerItemDecoration(this,
                    DividerItemDecoration.VERTICAL_LIST));
        }
    
        private void initDatas() {
            imgIds = new int[]{R.mipmap.pic01, R.mipmap.pic02, R.mipmap.pic03, R.mipmap.pic04,
                    R.mipmap.pic05, R.mipmap.pic06, R.mipmap.pic07};
            mDatas = new ArrayList<>();
            mDatas.add("亳州"); // 亳[bó]属于不常见的二级汉字
            mDatas.add("大娃");
            mDatas.add("二娃");
            mDatas.add("三娃");
            mDatas.add("四娃");
            mDatas.add("五娃");
            mDatas.add("六娃");
            mDatas.add("七娃");
            mDatas.add("喜羊羊");
            mDatas.add("美羊羊");
            mDatas.add("懒羊羊");
            mDatas.add("沸羊羊");
            mDatas.add("暖羊羊");
            mDatas.add("慢羊羊");
            mDatas.add("灰太狼");
            mDatas.add("红太狼");
            mDatas.add("孙悟空");
            mDatas.add("黑猫警长");
            mDatas.add("舒克");
            mDatas.add("贝塔");
            mDatas.add("海尔");
            mDatas.add("阿凡提");
            mDatas.add("邋遢大王");
            mDatas.add("哪吒");
            mDatas.add("没头脑");
            mDatas.add("不高兴");
            mDatas.add("蓝皮鼠");
            mDatas.add("大脸猫");
            mDatas.add("大头儿子");
            mDatas.add("小头爸爸");
            mDatas.add("蓝猫");
            mDatas.add("淘气");
            mDatas.add("叶峰");
            mDatas.add("楚天歌");
            mDatas.add("江流儿");
            mDatas.add("Tom");
            mDatas.add("Jerry");
            mDatas.add("12345");
            mDatas.add("54321");
            mDatas.add("_(:з」∠)_");
            mDatas.add("……%￥#￥%#");
        }
    }

**拓展：** 同样，我们也可以自定义分割线的样式。

在drawable目录下自定义样式divider\_item.xml

<?xml version="1.0" encoding="utf-8"?>
    <shape xmlns:android="http://schemas.android.com/apk/res/android"
        android:shape="rectangle">
    
        <size android:height="2dp"/>
        <gradient android:startColor="#00FF00"
            android:centerColor="#FFFF00"
            android:endColor="#FF0000"
            android:type="linear"/>
    
    </shape>

在values目录的styles.xml文件中引用自定义的分割线样式

<resources>
    
        
        <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
            
            <item name="colorPrimary">@color/colorPrimary</item>
            <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
            <item name="colorAccent">@color/colorAccent</item>
    
            <item name="android:listDivider">@drawable/divider_item</item>
        </style>
    
    </resources>

> item name=”android:listDivider”>@drawable/divider\_item

就这样我们完成了RecyclerView分割线的定义，我们可以自定义我们分割线的样式，让分割线更加绚丽多彩。

[SouthEast]: /images/20220604/b36bc21e459f4b929de0b10df479b917.png