RecyclerView线性分割线

 

由于recyclerview默认是没有分割线的，需要显示分割线的话，可以在布局里添加一条有背景色的View标签，或者通过ItemDecoration来实现，本文以后者为例。

ItemDecoration里有2个重要的方法，onDraw和getItemOffsets。

class MyItemDecoration extends RecyclerView.ItemDecoration { private int mOrientation = LinearLayout.VERTICAL; private Drawable mDivider; MyItemDecoration(Context context) { int[] rids = new int[]{android.R.attr.listDivider};//系统自带的属性，宽高各2dp
        TypedArray typedArray = context.obtainStyledAttributes(rids); mDivider = typedArray.getDrawable(0); typedArray.recycle(); } void setOrientation(int orientation) { mOrientation = orientation; } int getOrientation() { return mOrientation; } @Override public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) { super.onDraw(c, parent, state); ((LinearLayoutManager) parent.getLayoutManager()).setOrientation(mOrientation); if (mDivider != null) { //需要传入画布和当前recyclerview
            if (mOrientation == LinearLayout.HORIZONTAL) { drawHorizontal(c, parent); } else { drawVertical(c, parent); } } } //绘制竖直方向的横线
    private void drawVertical(Canvas c, RecyclerView parent) { int left = parent.getPaddingLeft();//横线左右随父容器
        int right = parent.getWidth() - parent.getPaddingRight(); for (int i = 0; i < parent.getChildCount(); i++) { //遍历recyclerview的每个子view
            View child = parent.getChildAt(i); //分割线的top,left,right,bottom
            int top = child.getBottom(); int bottom = child.getBottom() + mDivider.getIntrinsicHeight(); mDivider.setBounds(left, top, right, bottom);//设置分割线的区域
            mDivider.draw(c);//绘制到画布
 } } //绘制水平方向的竖线
    private void drawHorizontal(Canvas c, RecyclerView parent) { int top = parent.getPaddingTop();//竖线上下随父容器
        int bottom = parent.getBottom(); for (int i = 0; i < parent.getChildCount(); i++) { //遍历recyclerview的每个子view
            View child = parent.getChildAt(i); //分割线的top,left,right,bottom
            int left = child.getRight(); Log.d("TAG", "LEFT:" + left); int right = left + mDivider.getIntrinsicWidth(); mDivider.setBounds(left, top, right, bottom);//设置分割线的区域
            mDivider.draw(c);//绘制到画布
 } } @Override public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) { super.getItemOffsets(outRect, view, parent, state); //item之间的位移量
        if (mOrientation == LinearLayout.HORIZONTAL) { outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0); } else { outRect.set(0, 0, 0, mDivider.getIntrinsicHeight()); } } }

布局文件activity_main

<LinearLayout 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" android:orientation="vertical" tools:context="com.jogger.animatorpathdemo.MainActivity">

    <Button android:id="@+id/btn_add" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="添加"/>

    <Button android:id="@+id/btn_reduce" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="移除"/>

    <Button android:id="@+id/btn_change" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="切换orientation"/>

    <android.support.v7.widget.RecyclerView android:id="@+id/rv_content" android:layout_width="match_parent" android:layout_height="wrap_content"/>
</LinearLayout>

MainActivity

public class MainActivity extends AppCompatActivity implements View.OnClickListener { private RecyclerView rv_content; private MyAdapter mAdapter; private Button btn_add; private Button btn_reduce; private Button btn_change; private int mPos; private MyItemDecoration mMyItemDecoration; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); rv_content = (RecyclerView) findViewById(R.id.rv_content); mAdapter = new MyAdapter(this); rv_content.setLayoutManager(new LinearLayoutManager(this)); rv_content.setAdapter(mAdapter); rv_content.setItemAnimator(new DefaultItemAnimator());//默认添加动画
        mMyItemDecoration = new MyItemDecoration(this); mMyItemDecoration.setOrientation(LinearLayout.HORIZONTAL);//设置方向
 rv_content.addItemDecoration(mMyItemDecoration); btn_add = (Button) findViewById(R.id.btn_add); btn_reduce = (Button) findViewById(R.id.btn_reduce); btn_change = (Button) findViewById(R.id.btn_change); btn_add.setOnClickListener(this); btn_reduce.setOnClickListener(this); btn_change.setOnClickListener(this); } @Override public void onClick(View view) { switch (view.getId()) { case R.id.btn_add: mAdapter.addItem(mPos); mPos++; if (mPos > 50) { mPos = 50; } break; case R.id.btn_reduce: mPos--; if (mPos < 0) { mPos = 0; } mAdapter.removeItem(mPos); break; case R.id.btn_change: if (mMyItemDecoration.getOrientation() == LinearLayout.HORIZONTAL) { mMyItemDecoration.setOrientation(LinearLayout.VERTICAL);//设置方向
                } else { mMyItemDecoration.setOrientation(LinearLayout.HORIZONTAL);//设置方向
 } rv_content.addItemDecoration(mMyItemDecoration); break; } } }

适配器MyAdapter

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> { private Context mContext; private List<String> mList; public MyAdapter(Context context) { mContext = context; mList = new ArrayList<>(); } public void addItem(int pos) { mList.add(pos, "android--->" + pos); notifyItemInserted(pos); } public void removeItem(int pos) { mList.remove(pos); notifyItemChanged(pos); } @Override public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { return new MyViewHolder(LayoutInflater.from(mContext).inflate(R.layout.rv_item, parent, false)); } @Override public void onBindViewHolder(MyViewHolder holder, int position) { holder.tv_content.setText(mList.get(position)); } @Override public int getItemCount() { return mList.size(); } class MyViewHolder extends RecyclerView.ViewHolder { TextView tv_content; MyViewHolder(View itemView) { super(itemView); tv_content = (TextView) itemView.findViewById(R.id.tv_content); } } }