RecyclerView 使用方法总结（一）：RecyclerView的基本用法，及实现ListView

参考资源：http://blog.youkuaiyun.com/developer_jiangqq/article/details/49992269?hmsr=toutiao.io&utm_medium=toutiao.io&utm_source=toutiao.io

一、为什么叫RecyclerView?

• 不关注item是否显示在正确位置，是否显示正确
• 不关注item是如何分割的，即不关注分割线
• 不关注item增加和删除的动画效果
• 仅仅关注如何回收和复用itemView

备注

1. item的位置是由 LayoutManager 决定的
2. item的分割线是由ItemDecoration 决定的
3. item的动画效果是由ItemAnimator 决定的

二、RecyclerView能干什么？

三、RecyclerView的相关配置

步骤：Files -> Project Structure ->app(需要关联的Module) -> Dependencies ->”+”(加号) ->recyclerview-v7(选择该依赖) -> ok -> ok

备注：使用RecyclerView的时候一定要把包名写完整，如：

否则不会识别RecyclerView。

四、RecyclerView的实现

1、Just Like ListView（无下拉刷新和加载更多）
①定义一个分割线：DividerItemDecoration.java

public class DividerItemDecoration extends RecyclerView.ItemDecoration
{

    private static final int[] ATTRS = new int[] { android.R.attr.listDivider };

    public static final int HORIZONTAL_LIST = LinearLayoutManager.HORIZONTAL;

    public static final int VERTICAL_LIST = LinearLayoutManager.VERTICAL;

    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)
    {
        Log.v("itemdecoration", "onDraw()");
         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, int itemPosition,
            RecyclerView parent)
    {
        if (mOrientation == VERTICAL_LIST)
        {
            outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());
        } else
        {
            outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);
        }
    }
}

②定义Adapter和ViewHolder:
MyViewHolder

public class MyViewHolder extends RecyclerView.ViewHolder {

    protected TextView textView;
    public MyViewHolder(View itemView) {
        super(itemView);

        textView = (TextView) itemView.findViewById(R.id.text_view);
    }
}

适配器：RecyclerViewAdapter

 public class RecyclerViewAdapter extends RecyclerView.Adapter<MyViewHolder>{

    private Context mContext;
    private LayoutInflater mInflater;
    private List<String> mDatas;

    public RecyclerViewAdapter(Context context,List<String> datas) {

        this.mContext = context;
        this.mDatas = datas;
        mInflater = LayoutInflater.from(mContext);
    }

    @Override
    public void onBindViewHolder(MyViewHolder holder, int position) {
        holder.textView.setText(mDatas.get(position));
    }

    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

        View view = mInflater.inflate(R.layout.item,parent,false);
        MyViewHolder mMyViewHolder = new MyViewHolder(view);
        return mMyViewHolder;
    }

    @Override
    public int getItemCount() {
        return mDatas.size();
    }
}

③布局文件：
activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#ffffff"
    >

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

</RelativeLayout>

item.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="70dp"
    android:background="#d1da1b"
    >

    <TextView
        android:id="@+id/text_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:textSize="15sp"
        android:textColor="#ffffff"
        android:gravity="center"
        />

</LinearLayout>

④界面Activity：MainActivity.java

public class MainActivity extends Activity {

    private RecyclerView mRecyclerView;
    private List<String> mDatas;
    private RecyclerViewAdapter mAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        initDatas();
        initView();

        mAdapter = new RecyclerViewAdapter(this,mDatas);
        mRecyclerView.setAdapter(mAdapter);


        LinearLayoutManager mLinearLayoutManager = new LinearLayoutManager(this,LinearLayoutManager.VERTICAL,false);
        mRecyclerView.setLayoutManager(mLinearLayoutManager);

        mRecyclerView.addItemDecoration(new DividerItemDecoration(this,DividerItemDecoration.VERTICAL_LIST));
    }

    private void initDatas(){
        mDatas = new ArrayList<>();

        for (int i = 'A';i<='z';i++){
            mDatas.add(""+(char)i);
        }
    }

    private void initView(){
        mRecyclerView = (RecyclerView) findViewById(R.id.recycler_view);
    }
}

到此，ListView的效果就成功地实现了

备注：实现自定义分割线
①在drawable文件夹下新建一个xml文件，shape类型的，如下：

divider.xml的内容如下：

②android每个工程都会有一个默认的主题，如：

③在这个主题的styles.xml文件中添加一个item,如下红线部分：

android:listDivider与分割线DividerItemDecoration.java文件中的ATTRS中的元素相对应，android.R.attr.listDivider是android自带的属性。

最终效果图如下：

其他添加分割线：在子布局中添加android:layout_margin=”5dp”属性，如下：
item.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="70dp"
    android:background="#d1da1b"
    android:layout_margin="5dp"
    >
    <TextView
        android:id="@+id/text_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:textSize="15sp"
        android:textColor="#ffffff"
        android:gravity="center"
        />
</LinearLayout>

这种方法的结果是RecyclerView的背景是什么颜色，分割线就是什么颜色，而且item的背景有重复的颜色，性能不太好

RecyclerView使用总结的全部代码下载请点我

下篇将介绍有下拉刷新和加载更多的仿ListView的RecyclerView