我写了一个简单的登录demo，用的是传统的Data Binding来实现Android的MVVM架构。对于MVVM我觉得是对MVP架构中P层的一次升华，进一步的解耦，同时view与model又是双向绑定，这种绑定又是支持生命周期检测，不用担心页面销毁了还有回调出现，不需要findViewById也不需要butterknife，不需要拿到具体的View去设置数据绑定监听器等等，全由data binding帮我们完成。

build.gradle(app)

dataBinding{
        enabled=true
 }

布局

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"
    xmlns:tools="http://schemas.android.com/tools">
    <data>
        <variable
            name="viewModel"
            type="com.leostadyn.stackfarm.mvvmtest.UserViewModel" />
    </data>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        tools:context=".MainActivity">
        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@={viewModel.user.status}"
            android:id="@+id/txt_user_login_status"/>
        <EditText
            android:id="@+id/edit_username"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@={viewModel.user.userName}"
            android:hint="username"/>
        <EditText
            android:id="@+id/edit_password"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@={viewModel.user.password}"
            android:hint="password"/>
        <Button
            android:id="@+id/btn_submit"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:textAllCaps="false"
            android:onClick="click"
            android:text="submit"/>

        <ProgressBar
            android:id="@+id/progressBar"
            android:visibility="gone"
            style="?android:attr/progressBarStyle"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />


    </LinearLayout>
</layout>

Model

User.java

import android.databinding.ObservableField;
//User模型
public class User {
    //用户名
    public ObservableField<String >userName=new ObservableField<>();
    //密码
    public ObservableField<String >password=new ObservableField<>();
    //反馈
    public ObservableField<String >status=new ObservableField<>();

    public User() {
    }
}

ViewModel

UserViewModel.java

import android.content.Context;
import android.util.Log;
import com.leostadyn.stackfarm.mvvmtest.databinding.ActivityMainBinding;
public class UserViewModel {
    private Context context;
    private ActivityMainBinding activityMainBinding;
    public static final String TAG="KKKKKKK";
    public User user;
    public UserLocalData data;
    public UserViewModel(Context context, ActivityMainBinding activityMainBinding){
        this.context=context;
        this.activityMainBinding=activityMainBinding;
    }
    public void init(){
        this.user=new User();
        this.activityMainBinding.setViewModel(UserViewModel.this);
        data=new UserLocalData();
    }
    //登录
    public void login(){
        //业务逻辑
        Log.e(TAG,"status:"+user.status.get());
        Log.e(TAG,"username:"+user.userName.get());
        Log.e(TAG,"password:"+user.password.get());
        //权限的校验
        if (data.findByUser(this.user))
            this.user.status.set("success");
        else
            this.user.status.set("error");
    }
}

View

MainActivity.java

public class MainActivity extends AppCompatActivity {
    UserViewModel userViewModel;
    ProgressBar progressBar;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
//        setContentView(R.layout.activity_main);
        ActivityMainBinding dataBindingUtil=DataBindingUtil.setContentView(MainActivity.this,R.layout.activity_main);
        userViewModel=new UserViewModel(MainActivity.this,dataBindingUtil);
        progressBar=findViewById(R.id.progressBar);
    }
    @Override
    protected void onStart() {
        super.onStart();
        userViewModel.init();
    }
    public void click(View view) {
        progressBar.setVisibility(View.VISIBLE);
        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                userViewModel.login();
                progressBar.setVisibility(View.GONE);
            }
        },2000);
    }
}

模拟数据处理

public class UserLocalData {
    //模拟数据库
    String [] userArray={"user1:password1","user2:password2"};
    public UserLocalData() {
    }
    //查找用户
    public boolean findByUser(User user){
        if(user==null)
            throw  new NullPointerException("this user object is null");
        for (int i = 0; i <userArray.length; i++) {
            String  userStr=userArray[i];
            String [] userArray=userStr.split(":");
            String username=userArray[0];
            String password=userArray[1];
            if((user.userName.get()).equals(username)&& (user.password.get()).equals(password)){
                return true;
            }
        }
        return false;
    }
}