RecyclerVeiw的学习（一）

天高任鸟飞，海阔凭鱼跃

recyclerView的最初实现

现在recyclerView的使用越来越广泛，多条目，多布局，局部刷新，动态改变布局，item的拖拽等等，recyclerView的灵活性是listView不能媲美的地方。今天这篇文章先简单的介绍下recyclerView的简单使用。

先看布局中的代码,只有一个recyclerVeiw

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    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/id_recyclerView"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</RelativeLayout>

compile 'com.android.support:recyclerview-v7:25.0.1'
compile 'com.android.support:cardview-v7:25.0.1'
 compile 'com.github.bumptech.glide:glide:3.7.0'

接下啦看看主程序

public class MainActivity extends AppCompatActivity {

    private RecyclerView mRecyclerView;
    private Fruit[] fruits = {new Fruit("Apple", R.mipmap.apple), new Fruit("Banana", R.mipmap.banana),
            new Fruit("Orange", R.mipmap.orange), new Fruit("Watermelon", R.mipmap.watermelon),
            new Fruit("Pear", R.mipmap.pear), new Fruit("Grape", R.mipmap.grape),
            new Fruit("Pineapple", R.mipmap.pineapple), new Fruit("Strawberry", R.mipmap.strawberry),
            new Fruit("Cherry", R.mipmap.cherry), new Fruit("Mango", R.mipmap.mango)};
    private List<Fruit> fruitList = new ArrayList<>();
    private FruitAdapter adapter;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initFruits();
        intiViews();
        GridLayoutManager layoutManager = new GridLayoutManager(this, 3);
        mRecyclerView.setLayoutManager(layoutManager);
        adapter = new FruitAdapter(fruitList);
        mRecyclerView.setAdapter(adapter);

    }

    private void intiViews() {
        mRecyclerView= (RecyclerView) findViewById(R.id.id_recyclerView);
    }

    private void initFruits() {
        fruitList.clear();
        for (int i = 0; i < 50; i++) {
            Random random = new Random();
            int index = random.nextInt(fruits.length);
            fruitList.add(fruits[index]);
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();
        switch (id){
            case R.id.action_add:
                adapter.addData(1);
                break;
            case R.id.action_delete:
                adapter.deleteData(1);
                break;
            case R.id.action_gridview:
                mRecyclerView.setLayoutManager(new GridLayoutManager(this,3));
                break;
            case R.id.action_listview:
                mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
                break;
            case R.id.action_staggered:
                startActivity(new Intent(this,StaggeredGridLayoutActivity.class));

                break;
            case R.id.action_hor_gridview:
                mRecyclerView.setLayoutManager(new StaggeredGridLayoutManager(5,StaggeredGridLayoutManager.HORIZONTAL));
                break;
        }

        return super.onOptionsItemSelected(item);
    }
}

recyclerView这里的初始化方法要注意下,layoutManager有三种，在menu中我将切换布局就是设置不同的layoutManager.

• GridLayoutManager layoutManager = new GridLayoutManager(this, 3);

• mRecyclerView.setLayoutManager(layoutManager);

这里用到了menu，菜单里面设置了几个方法，增加，删除一个。切换布局等

<menu 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"
    tools:context=".MainActivity">
    <item
        android:id="@+id/action_add"
        android:orderInCategory="100"
        android:title="Add"
        android:icon="@mipmap/ic_menu_add"
        app:showAsAction="ifRoom" />
    <item
        android:id="@+id/action_delete"
        android:orderInCategory="100"
        android:title="Delete"
        android:icon="@mipmap/ic_menu_delete"
        app:showAsAction="ifRoom" />
    <item
        android:id="@+id/action_listview"
        android:orderInCategory="100"
        android:title="ListView"
        app:showAsAction="never" />
    <item
        android:id="@+id/action_gridview"
        android:orderInCategory="100"
        android:title="GridView"
        app:showAsAction="never" />
    <item
        android:id="@+id/action_hor_gridview"
        android:orderInCategory="100"
        android:title="HorizontalGridView"
        app:showAsAction="never" />
    <item
        android:id="@+id/action_staggered"
        android:orderInCategory="100"
        android:title="StaggeredGridView"
        app:showAsAction="never" />


</menu>

接下来看看Adapter

public class FruitAdapter extends RecyclerView.Adapter<FruitAdapter.ViewHolder> {

    private static final String TAG = "FruitAdapter";

    private Context mContext;

    private List<Fruit> mFruitList;

    static class ViewHolder extends RecyclerView.ViewHolder {
        CardView cardView;
        ImageView fruitImage;
        TextView fruitName;

        public ViewHolder(View view) {
            super(view);
            cardView = (CardView) view;
            fruitImage = (ImageView) view.findViewById(R.id.fruit_image);
            fruitName = (TextView) view.findViewById(R.id.fruit_name);
        }
    }

    public FruitAdapter(List<Fruit> fruitList) {
        mFruitList = fruitList;
    }

    public void addData(int pos) {
        mFruitList.add(new Fruit("Apple", R.mipmap.apple));
        notifyItemInserted(pos);
    }

    public void deleteData(int pos) {
        mFruitList.remove(pos);
        notifyItemRemoved(pos);
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        if (mContext == null) {
            mContext = parent.getContext();
        }
        View view = LayoutInflater.from(mContext).inflate(R.layout.fruit_item, parent, false);
        final ViewHolder holder = new ViewHolder(view);
        holder.cardView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(mContext, "点击了", Toast.LENGTH_SHORT).show();
            }
        });
        return holder;
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        Fruit fruit = mFruitList.get(position);
        holder.fruitName.setText(fruit.getName());
        Glide.with(mContext).load(fruit.getImageId()).into(holder.fruitImage);
    }

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

}

注意一下几点即可：

• 继承于RecyclerView.Adapter，里面传一个继承于RecyclerView.ViewHolder的对象，继承该对象后会重写构造方法，一般在这个构造方法里面实现item控件的初始化操作
• 继承RecyclerView.Adapter方法后会实现两个方法
  • onCreateViewHolder（）该方法返回一个实现了的Viewholder对象，在该方法中初始化布局。
• onBindViewHolder（）该方法主要做绑定数据方法

关于实现item的分割线的问题，文档上说

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

这里我也将提供DividerItemDecoration类

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;

/**
 * This class is from the v7 samples of the Android SDK. It's not by me!
 * <p/>
 * See the license above for details.
 */
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;   //item间隔图片资源

    private int mOrientation;   //方向

    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("recyclerview - 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);       //绘制
        }
    }

    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);
        }
    }
}

而我的一般做法是在item 的布局中设置margin或者padding.

好了今天这里介绍recyclerView的简单用法，最后附上gif图一张

recylerVeiw--1.gif

参考文献：http://blog.csdn.net/lmj623565791/article/details/45059587