app下的build.gradle中添加

 dataBinding{
        enabled true
    }

MVVM的基本使用

activity_main.xml

<?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>
        <!--此处定义该布局要用的数据的名称和类型-->
        <variable
            name="user"
            type="com.example.myapplication.User"/>
    </data>
    <!--下面的内容就和平时的布局文件一样-->
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">
        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            app:header="@{user.header}"
            />
        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:gravity="center"
            android:text="@{`姓名：`+user.name}"/>
        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:gravity="center"
            android:text="@{`密码:`+user.password}"/>

    </LinearLayout>


</layout>

User.java

public class User extends BaseObservable{
    private String name;
    private String password;

    private String header;

    public String getHeader() {
        return header;
    }

    public void setHeader(String header) {
        this.header = header;
    }

    public User(String name, String password,String header) {
        this.name = name;
        this.password = password;
        this.header=header;
    }
    @Bindable
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
        notifyPropertyChanged(BR.name);
    }
    @Bindable
    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
        notifyPropertyChanged(BR.password);
    }

    //自定义属性:提供一个静态方法来加载image
    @BindingAdapter("bind:header")
    public static void getImage(ImageView view,String url){
        Picasso.with(view.getContext()).load(url).into(view);
    }
}

MainActivity.java

public class MainActivity extends AppCompatActivity {
    private Handler handler = new Handler();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
//        setContentView(R.layout.activity_main);

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

        final User user = new User("napolean","123",
                "http://b-ssl.duitang.com/uploads/blog/201312/04/20131204184148_hhXUT.jpeg");
        activityMainBinding.setUser(user);

        handler.postDelayed(new Runnable() {
            @Override
            public void run() {
                user.setName("lisi");
                user.setPassword("123456");
            }
        },3000);
    }
}

MVVM中使用ListView
item.xml

<?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>
        <variable
            name="user"
            type="com.example.myapplication.User" />
    </data>
    
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">
        <ImageView
            android:layout_width="50dp"
            android:layout_height="50dp"
            app:header="@{user.header}" />
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:gravity="center"
            android:text="@{user.name}" />
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:gravity="center"
            android:onClick="@{user.click}"
            android:text="@{user.password}" />
    </LinearLayout>
</layout>

CommAdapter.java

public class CommAdapter<T> extends BaseAdapter {
    private Context context;
    private LayoutInflater inflater;
    private int layoutId;
    //variable的ID，，自动生成
    private int variableId;

    private List<T> list;

    public CommAdapter(Context context, LayoutInflater inflater, int layoutId, int variableId, List<T> list) {
        this.context = context;
        this.inflater = inflater;
        this.layoutId = layoutId;
        this.variableId = variableId;
        this.list = list;
    }

    @Override
    public int getCount() {
        return list.size();
    }

    @Override
    public Object getItem(int position) {
        return list.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewDataBinding dataBinding;
        if(convertView==null){
            dataBinding= DataBindingUtil.inflate(inflater,layoutId,parent,false);
        }else{
            //重用之前的
            dataBinding=DataBindingUtil.getBinding(convertView);
        }
        dataBinding.setVariable(variableId,list.get(position));
        return dataBinding.getRoot().getRootView();
    }
}

MainActivity.java

public class MainActivity extends AppCompatActivity {
    ListView list;
    List<User> data=new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        list= (ListView) findViewById(R.id.listView);
        data.add(new User("https://goss1.vcg.com/creative/vcg/800/new/VCG41N104285826.jpg","1","1"));
        data.add(new User("https://goss1.vcg.com/creative/vcg/800/new/VCG41N104285826.jpg","2","2"));
        data.add(new User("https://goss1.vcg.com/creative/vcg/800/new/VCG41N104285826.jpg","3","3"));
        data.add(new User("https://goss1.vcg.com/creative/vcg/800/new/VCG41N104285826.jpg","4","4"));
        list.setAdapter(new CommAdapter<User>(this,getLayoutInflater(),R.layout.item, BR.user,data));
    }
}