android5.0中RecycleView的用法

 最近学习了android5.0中新增的一个组件RecycleView，是用来代替当前的listview开发的，是因为在RecycleView中已经有了viewholder缓存，并且不同的item之间可以设置不同的布局。能非常有效地维护了意见数量有限，滚动大的数据集。使用 RecyclerView当你拥有的数据的集合，它的元素在运行时改变基于用户行为和网络事件的小部件

首先看看RecyclerView的一个小例子：

需要引入：android-support-v7-appcompat.jar

          android-v7-RecyclerView.jar来支持低版本的android系统

新建一个my_layout.xml布局文件：里边放置一个RecyclerView

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

在之前的listview开发中，我们需要自定义viewholder来缓存listView中的数据，而在RecyclerView中，已经封装好了viewholder在adapter中，接下来自定义我们的adapter

public class MyAdapter2 extends RecyclerView.Adapter<MyAdapter2.ViewHolder>
{
    // 数据集
    private String[] mDataset;

    public MyAdapter2(String[] dataset)
    {
        super();
        mDataset = dataset;
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int i)
    {

        // 创建一个View，简单起见直接使用系统提供的布局，就是一个TextView

        View view = View.inflate(viewGroup.getContext(),R.layout.viewholder_item, null);

        // 创建一个ViewHolder

        ViewHolder holder = new ViewHolder(view);

        return holder;

    }

    @Override
    public void onBindViewHolder(ViewHolder viewHolder, int i)
    {

        // 绑定数据到ViewHolder上

        viewHolder.mTextView.setText(mDataset[i]);

    }

    @Override
    public int getItemCount()
    {

        return mDataset.length;

    }

    public static class ViewHolder extends RecyclerView.ViewHolder
    {

        public TextView mTextView;

        public ViewHolder(View itemView)
        {

            super(itemView);

//          mTextView = (TextView) itemView;
            mTextView = (TextView) itemView.findViewById(R.id.view_text_id);

        }

    }

}

在activity这样调用，并设置adapter

RecyclerView recyclerView = (RecyclerView) findViewById(R.id.rvlist);

         // 创建一个线性布局管理器

         LinearLayoutManager layoutManager = new LinearLayoutManager(this);

         layoutManager.setOrientation(LinearLayoutManager.VERTICAL);

         // 设置布局管理器

         recyclerView.setLayoutManager(layoutManager);

         // 创建数据集
         String[] dataset = new String[100];

         for (int i = 0; i < dataset.length; i++){

         dataset[i] = "item" + i;

         }

         // 创建Adapter，并指定数据集

        MyAdapter2 adapter = new MyAdapter2(dataset);

         // 设置Adapter

         recyclerView.setAdapter(adapter);

         }

运行效果：

在这个例子中只是用到了最基本的布局，下面结合android中新增的CardView和RecycleView实现一个复杂的布局：

先看效果图：

CardView继承自FrameLayout，允许你在card视图中显示信息. CardView也可以设置阴影和圆角。（其实现在很多应用都自定义了Card视图，Google这回将card视图作为基本控件，可以拿来直接使用了）

Layout中为CardView设置圆角使用card_view:cardCornerRadius属性

代码中为CardView设置圆角使用CardView.setRadius方法

为CardView设置背景颜色使用card_view:cardBackgroundColor属性

1.在item布局中引入cardview组件

<android.support.v7.widget.CardView
      android:id="@+id/cardview_id"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      app:cardCornerRadius="5dp"
      app:cardElevation="0dp" >

      <RelativeLayout
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          android:padding="5dp" >

          <ImageView
              android:id="@+id/image_id"
              android:layout_width="20dp"
              android:layout_height="20dp"
              android:layout_alignParentLeft="true"
              />

          <TextView
              android:id="@+id/text_id"
              android:layout_width="wrap_content"
              android:layout_height="match_parent"
              android:textColor="#f89ef5"
              android:textSize="20dp"
              android:layout_centerInParent="true" />
      </RelativeLayout>
  </android.support.v7.widget.CardView>

需要注意的是要在最底层的layout中引入cardview的命名空间：

xmlns:app=http://schemas.android.com/apk/res-auto

要实现不同的item有不同的布局，需要有一个type字段来作为区分，这里，我新建一个UserInfo类，如下：

public class UserInfo {

    public static final int hasImage = 1;
    public static final int noImage = 2;

    private String mUserName;
    private int userImage;

    int type;

    public String getmUserName() {
        return mUserName;
    }

    public void setmUserName(String mUserName) {
        this.mUserName = mUserName;
    }

    public int getUserImage() {
        return userImage;
    }

    public void setUserImage(int userImage) {
        this.userImage = userImage;
    }

    public int getType() {
        return type;
    }

    public void setType(int type) {
        this.type = type;
    }

    public UserInfo(String mUserName, int type) {
        this.mUserName = mUserName;
        this.type = type;
    }

    public UserInfo(String mUserName, int userImage, int type) {
        this.mUserName = mUserName;
        this.userImage = userImage;
        this.type = type;
    }
}

hasImage和noImage分别表示该item需不需要加载图片，来加载不同的布局。

接下来看看Adapter的代码：

public class MyAdapter extends RecyclerView.Adapter<ViewHolder>{

    private List<UserInfo>mList = null;
    private Context context = null;

    public MyAdapter(List<UserInfo> mList, Context context) {
        super();
        this.mList = mList;
        this.context = context;
        //      for (int i = 0; i < mList.size(); i++) {
        //          Log.d("liuhang","==="+mList.get(i).getmUserName()+"==="+mList.get(i).getUserImage());
        //      }
    }

        public void addToList(UserInfo info,int position) {
            mList.add(0, info);
            notifyItemInserted(position);
            notifyDataSetChanged();
        }


    public class TextOnClick implements OnClickListener {
        private int position = 0;

        public TextOnClick(int position) {
            this.position = position;
        }


        @Override
        public void onClick(View v) {
            Toast.makeText(context,"text the name:"+mList.get(position).getmUserName(),1000).show();
        }
    }

    public class ImageOnclick implements OnClickListener {
        private int position = 0;

        public ImageOnclick(int position) {
            this.position = position;
        }
        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            Toast.makeText(context,"image the imageId:"+mList.get(position).getUserImage(),1000).show();
        }
    }

    public class ItemOnClick implements OnItemClickListener {

        @Override
        public void onItemClick(AdapterViewCompat<?> arg0, View arg1, int arg2,
                long arg3) {
            // TODO Auto-generated method stub
            Toast.makeText(context,"you choose the item",1000).show();
        }

    }



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

    public class TextViewHolder extends RecyclerView.ViewHolder {
        public TextView textView = null;
        public TextViewHolder(View view) {
            super(view);
            this.textView = (TextView) view.findViewById(R.id.text_id);
        }
    }

    public class ImageTextViewHolder extends RecyclerView.ViewHolder {
        public ImageView imageView = null;
        public TextView textView = null;
        public ImageTextViewHolder(View view) {
            super(view);
            this.imageView = (ImageView) view.findViewById(R.id.image_id);
            this.textView = (TextView) view.findViewById(R.id.text_id);
        }



    }



    @Override
    public int getItemViewType(int position) {
        // TODO Auto-generated method stub
        return mList.get(position).getType();
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        switch (getItemViewType(position)) {
        case UserInfo.hasImage:
            ImageTextViewHolder imageTextViewHolder = (ImageTextViewHolder) holder;
            imageTextViewHolder.imageView.setImageResource(mList.get(position).getUserImage());
            imageTextViewHolder.textView.setText(mList.get(position).getmUserName());
            imageTextViewHolder.textView.setOnClickListener(new TextOnClick(position));
            imageTextViewHolder.imageView.setOnClickListener(new ImageOnclick(position));
            break;
        case UserInfo.noImage:
            TextViewHolder textViewHolder = (TextViewHolder) holder;
            textViewHolder.textView.setText(mList.get(position).getmUserName());
            textViewHolder.textView.setOnClickListener(new TextOnClick(position));
        }
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int type) {
        ViewHolder holder = null;
        View view = null;
        switch (type) {
        case UserInfo.hasImage:
            view = LayoutInflater.from(parent.getContext()).inflate(R.layout.card_text_image_item,null);
            holder = new ImageTextViewHolder(view);
            break;
        case UserInfo.noImage:
            view = LayoutInflater.from(parent.getContext()).inflate(R.layout.card_text_item,null);
            holder = new TextViewHolder(view);
            break;
        }
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        return holder;
    }

}

在activity中这样调用：

RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recycler_id);
        recyclerView.setHasFixedSize(true);

        LinearLayoutManager linaLayout = new LinearLayoutManager(this);
        linaLayout.setOrientation(1);

        recyclerView.setLayoutManager(linaLayout);

        recyclerView.getRecycledViewPool().setMaxRecycledViews(0, 10);

        int[]userImage = {R.drawable.icon08,R.drawable.icon00,R.drawable.icon01,
                                  R.drawable.icon02,R.drawable.icon03,R.drawable.icon04,
                                  R.drawable.icon05,R.drawable.icon06,R.drawable.icon07};

        List<UserInfo>userList = new ArrayList<UserInfo>();

        int position = 0;
        for (int i = 0; i < 35; i++) {
            position = (int) (Math.random() * 8);
            UserInfo userInfo1 = new UserInfo("zhangsan"+i,2);
            UserInfo userInfo2 = new UserInfo("lisi"+i,userImage[position],1);
            userList.add(userInfo1);
            userList.add(userInfo2);
        }

        final MyAdapter adapter= new MyAdapter(userList, this);
        recyclerView.setAdapter(adapter);

        recyclerView.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                Toast.makeText(MyActivity.this,"you choose the item",1000).show();
            }
        });

        Button button = (Button) findViewById(R.id.add);
        button.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                adapter.addToList(new UserInfo("new add"+ newAdd++, 2),0);
            }
        });