Android官方DataBinding（三）：RecyclerView 使用ViewDataBinding更新数据

本例基于Android官方DataBinding，在RecyclerView上实现一个简单需求：点击一个button按钮，增加一个数据元素，并更新的view上。

（1）首先写一个布局，这个布局上面放一个按钮button，下面一个标准Android RecyclerView。Button按钮的实现一个简单的功能：没点击一次就增加一个数据元素，然后更新到RecyclerView。recycler_view_layout.xml：

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

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

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

（2）和附录文章1,2，写数据模型User，对比这个User和附录1,2的User建模时候的异同，User.java：

package zhangphil.test;

import android.databinding.BaseObservable;
//import android.databinding.Bindable;

/**
 * Created by Phil on 2017/8/17.
 */

public class User extends BaseObservable {
    private String id;
    private String name;
    private String blog;

    public void setId(String id) {
        this.id = id;
        //notifyPropertyChanged(BR.id);
    }

    //@Bindable
    public String getId() {
        return this.id;
    }


    public void setName(String name) {
        this.name = name;
        //notifyPropertyChanged(BR.name);
    }

    //@Bindable
    public String getName() {
        return this.name;
    }

    public void setBlog(String blog) {
        this.blog = blog;
        //notifyPropertyChanged(BR.blog);
    }

    //@Bindable
    public String getBlog() {
        return this.blog;
    }
}

（3）因为是一个RecyclerView，RecyclerView需要Adapter，在Adapter中需要一个布局layout，为User的数据找到View，Adapter需要的子view布局这里将写View和Model的绑定代码，item.xml：

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">

    <data>

        <variable
            name="user"
            type="zhangphil.test.User" />
    </data>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <TextView
            android:id="@+id/id"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{user.id}"
            android:textColor="@android:color/holo_red_light" />

        <TextView
            android:id="@+id/name"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{user.name}"
            android:textColor="@android:color/holo_red_light" />

        <TextView
            android:id="@+id/blog"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{user.blog}"
            android:textColor="@android:color/holo_red_light" />

        <View
            android:layout_width="match_parent"
            android:layout_height="1px"
            android:background="@android:color/holo_blue_bright" />
    </LinearLayout>
</layout>

（4）上层Java代码，注意观察ViewHolder的写法。比较关键的是在创建ViewHolder时候传入的ViewDataBinding。在Adapter的onBindViewHolder里面，仅需两行代码就实现数据模型和View的绑定，MainActivity.java：

package zhangphil.test;

import android.databinding.DataBindingUtil;
import android.databinding.ViewDataBinding;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import java.util.ArrayList;

import static zhangphil.test.BR.user;

public class MainActivity extends AppCompatActivity {
    private int index = 0;

    private ItemAdapter mItemAdapter;
    private ArrayList<User> mItems;

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

        mItems = new ArrayList();
        for (int i = 0; i < 1; i++) {
            User u = new User();
            u.setId(index + "");
            u.setName("zhangphil @" + index);
            u.setBlog("blog.csdn.net/zhangphil @" + index);

            mItems.add(u);

            index++;
        }

        RecyclerView mRecyclerView = (RecyclerView) findViewById(R.id.recycler_view);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false));

        mItemAdapter = new ItemAdapter();
        mRecyclerView.setAdapter(mItemAdapter);

        findViewById(R.id.button).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                User u = new User();
                u.setId(index + "");
                u.setName("zhangphil @" + index);
                u.setBlog("blog.csdn.net/zhangphil @" + index);

                mItems.add(u);
                mItemAdapter.notifyDataSetChanged();

                index++;
            }
        });
    }


    private class ItemAdapter extends RecyclerView.Adapter<ItemViewHolder> {

        @Override
        public ItemViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
            ViewDataBinding binding = DataBindingUtil.inflate(LayoutInflater.from(viewGroup.getContext()), R.layout.item, viewGroup, false);
            ItemViewHolder holder = new ItemViewHolder(binding);
            return holder;
        }

        @Override
        public void onBindViewHolder(ItemViewHolder viewHolder, int i) {
            viewHolder.getBinding().setVariable(user, mItems.get(i));
            viewHolder.getBinding().executePendingBindings();
        }

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

    private class ItemViewHolder extends RecyclerView.ViewHolder {
        private ViewDataBinding binding;

        public ItemViewHolder(ViewDataBinding binding) {
            super(binding.getRoot());
            this.binding = binding;
        }

        public void setBinding(ViewDataBinding binding) {
            this.binding = binding;
        }

        public ViewDataBinding getBinding() {
            return this.binding;
        }
    }
}

代码运行结果，每点击一次button，数据增加一个，更新：

附录：
1，《Android官方DataBinding简例（一）》链接：http://blog.csdn.net/zhangphil/article/details/77322530  
2，《Android官方DataBinding（二）：动态数据更新notifyPropertyChanged》链接：http://blog.csdn.net/zhangphil/article/details/77328688