写一个简单的例子说明ObservableMap，ObservableArrayMap用法。
建立一个User.java的数据模型：

package zhangphil.test;

import android.databinding.BaseObservable;
import android.databinding.ObservableArrayMap;
import android.databinding.ObservableField;
import android.databinding.ObservableInt;
import android.databinding.ObservableMap;

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

public class User extends BaseObservable {
    public final ObservableInt id = new ObservableInt();
    public final ObservableField<String> name = new ObservableField<>();
    public final ObservableMap<String, Object> quality = new ObservableArrayMap<>();
    public final ObservableField<String> current = new ObservableField<>();
}

Keys.java：

package zhangphil.test;

/**
 * Created by Phil on 2017/8/18.
 */

public class Keys {
    public static final String current = "current_value";
}

activity_main.xml布局：

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

    <data>
        <import type="android.view.View" />
        <import type="zhangphil.test.Keys" />
        <import type="android.databinding.ObservableMap" />

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

    <LinearLayout
        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="更新" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{String.valueOf(user.id)}"
            android:textColor="@android:color/holo_red_light"
            android:visibility="@{ user.id > 0 ? View.VISIBLE : View.GONE }" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{user.name}"
            android:textColor="@{user.id == 0 ? @android:color/holo_red_light : @android:color/holo_blue_light}" />

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

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@{user.current}" />

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text=" --- " />

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@{user.quality[user.current]}" />
        </LinearLayout>
    </LinearLayout>
</layout>

MainActivity.java：

package zhangphil.test;

import android.databinding.DataBindingUtil;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;

import zhangphil.test.databinding.ActivityMainBinding;

public class MainActivity extends AppCompatActivity {

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

        ActivityMainBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_main);

        final User user = new User();
        binding.setUser(user);

        user.id.set(0);
        user.name.set("zhangphil");

        user.quality.put("normal", "N url");
        user.quality.put("high", "H url");
        user.quality.put("super", "S url");

        user.current.set("normal");

        binding.button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                user.id.set(1);
                user.quality.put("high", "new H url");
                user.current.set("high");
            }
        });
    }
}

代码运行结果，初始化状态：

点击更新按钮：

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   
3，《Android官方DataBinding（三）：RecyclerView 使用ViewDataBinding更新数据》链接：http://blog.csdn.net/zhangphil/article/details/77367432  
4，《Android官方DataBinding（四）：BindingAdapter》链接：http://blog.csdn.net/zhangphil/article/details/77374211