Android RecyclerView的使用（二）——添加分割线

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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

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>    <!-- Base application theme. -->    <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">        <!-- Customize your theme here. -->        <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。

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