闲话不多少，还是老套路，处理一个登陆的业务。详细的介绍MVVM我就不多说了，网上一大把，毕竟吹水还是我的弱项。
主要实现的功能有两个输入框，一个登陆按钮，两个TextView显示登陆结果。
秀一把我的LoginActivity

@BindLayout(R.layout.activity_login)
public class LoginActivity extends BaseActivity<ILoginViewModel, LoginActivityBriefnessor> implements ILoginView {
    @Override
    protected ILoginViewModel createViewModel(LoginActivityBriefnessor briefnessor) {
        return new LoginViewModel(this, briefnessor);
    }
}

是不是超级简洁，点击事件呢？怎么不见了，再看一看ViewModel

public class LoginViewModel extends BaseViewModel<ILoginView, ILoginModel, LoginActivityBriefnessor> implements ILoginViewModel {

    public LoginViewModel(ILoginView view, LoginActivityBriefnessor briefnessor) {
        super(view, briefnessor);
    }

    @Override
    protected ILoginModel createModel() {
        return new LoginModel(this);
    }

    @Override
    public void onLoginClick(String account, String pswd) {
        if (account.length() < 3) {
            Toast.makeText(context(), "账号不正确", Toast.LENGTH_SHORT).show();
            return;
        }
        if (pswd.length() < 3) {
            Toast.makeText(context(), "密码不正确", Toast.LENGTH_SHORT).show();
            return;
        }
        model.login(account, pswd);
    }

    @Override
    public void callbackLogin(LoginResult result) {
        briefnessor.setResult(result);
    }
}

ViewModel制作了登陆的数据验证，以及登陆回调的实现，model层完成模拟了登陆。
整个登陆的业务流程Activity并没有参与，在这其中就不得不提一个关键的中间件Briefness，它连接了View层与Model层，帮我们实现了数据绑定，以及事件传递。
我们先看一看布局是如何实现的

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    app:imports="com.hacknife.demo.bean.LoginResult,result"a
    app:viewModel="com.hacknife.demo.mvvm.viewmodel.ILoginViewModel"
    tools:ignore="MissingPrefix">

    <EditText
        android:id="@+id/et_account"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginHorizontal="40dp"
        android:layout_marginVertical="10dp"
        android:hint="账号" />

    <EditText
        android:id="@+id/et_pswd"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginHorizontal="40dp"
        android:layout_marginVertical="10dp"
        android:hint="密码" />

    <Button
        android:id="@+id/btn_login"
        android:layout_width="match_parent"
        android:layout_height="40dp"
        android:layout_marginHorizontal="40dp"
        android:layout_marginVertical="10dp"
        android:text="登陆"
        app:transfer="onLoginClick($et_account$,$et_pswd$)" />

    <LinearLayout style="@style/text_parent" android:layout_marginHorizontal="40dp">

        <TextView
            style="@style/text_childer"
            android:text="返回码" />

        <TextView
            android:id="@+id/tv_code"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            app:bind="$result.code$" />
    </LinearLayout>

    <LinearLayout style="@style/text_parent" android:layout_marginHorizontal="40dp">

        <TextView
            style="@style/text_childer"
            android:text="结果:" />

        <TextView
            android:id="@+id/tv_msg"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            app:bind="$result.msg$" />
    </LinearLayout>
</LinearLayout>

布局中，根布局绑定了ViewModel，以及用于展示登陆结果的数据源。登陆按钮传递单击登陆事件，剩下的两个textView绑定相应的字段。
同时在对应的Activity上绑定相应的布局文件，Briefness就能暂时他强大的功能了，它会自动生成[类名+Briefnessor]的类。

public class LoginActivityBriefnessor implements Briefnessor<LoginActivity> {
    public EditText et_account;
    public EditText et_pswd;
    public Button btn_login;
    public TextView tv_code;
    public TextView tv_msg;
    public LoginResult result;
    public ILoginViewModel viewModel;

    @Override
    public void bind(final LoginActivity host, Object source) {
        if (!Utils.contentViewExist(host)) {
            host.setContentView(R.layout.activity_login);
        }
        et_account = (EditText) host.findViewById(R.id.et_account);
        et_pswd = (EditText) host.findViewById(R.id.et_pswd);
        btn_login = (Button) host.findViewById(R.id.btn_login);
        tv_code = (TextView) host.findViewById(R.id.tv_code);
        tv_msg = (TextView) host.findViewById(R.id.tv_msg);
        btn_login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                viewModel.onLoginClick(et_account.getText().toString().trim() , et_pswd.getText().toString().trim());
            }
        });

    }

    @Override
    public void clear() {
        this.result = null;
        this.viewModel = null;
    }

    @Override
    public void clearAll() {
        this.result = null;
        this.viewModel = null;
        this.et_account = null;
        this.et_pswd = null;
        this.btn_login = null;
        this.tv_code = null;
        this.tv_msg = null;
    }
    @Override
    public void bindViewModel(Object viewModel) {
        this.viewModel = (ILoginViewModel) viewModel;
    }
    public void setResult(LoginResult result) {
        if (result == null) return;
        this.result = result;
        BriefnessInjector.injector(tv_code,result.getCode());
        BriefnessInjector.injector(tv_msg,result.getMsg());
    }
}

该类实现了数据绑定，以及向ViewModel发送消息附带输入框中的值。
Briefness的具体用法，请参考https://github.com/hacknife/briefness
下面说一说BaseActivity

public abstract class BaseActivity<T extends IBaseViewModel,B extends Briefnessor> extends AppCompatActivity implements IBaseView {
    protected T viewModel;
    protected B briefnessor;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        briefnessor = (B )Briefness.bind(this);
        viewModel = createViewModel(briefnessor);
        briefnessor.bindViewModel(viewModel);
        initView();
    }

    protected abstract T createViewModel(B briefnessor);


    @Override
    protected void onDestroy() {
        super.onDestroy();
        if (viewModel != null)
            viewModel.dettachView();
    }

    protected void initView() {
    }

    @Override
    public Context applicationContext() {
        return getApplication();
    }

    @Override
    public Activity context() {
        return this;
    }
}

BaseActivity中初始化了Briefness并创建ViewModel绑定到Briefness，并实现了IBaseView

public interface IBaseView {

    Context applicationContext();

    Activity context();
}

BaseViewModel继承AbsViewmodel并实现IBaseViewModel，持有Briefnessor，View，Model。

public abstract class BaseViewModel<V extends IBaseView, M extends IBaseModel, B extends Briefnessor> extends AbsViewModel<V> implements IBaseViewModel {

    protected V view;
    protected M model;
    protected B briefnessor;

    public BaseViewModel(V view, B briefnessor) {
        this.attachView(view);
        this.attachBriefnessor(briefnessor);
        this.view = getView();
        this.briefnessor = (B) getBriefnessor();
        model = createModel();
    }

    protected abstract M createModel();

    @Override
    public Context applicationContext() {
        return view.applicationContext();
    }

    @Override
    public Activity context() {
        return view.context();
    }
}

AbsViewModel 的作用主要是释放相应的连接关系。

public abstract class AbsViewModel<T> implements IBaseViewModel{
    protected WeakReference<T> mViewRef;
    protected WeakReference<Briefnessor> mBriefnessorRef;

    protected void attachView(T view) {
        mViewRef = new WeakReference<T>(view);
    }

    protected void attachBriefnessor(Briefnessor briefnessor) {
        mBriefnessorRef = new WeakReference<Briefnessor>(briefnessor);
    }

    protected T getView() {
        return mViewRef.get();
    }

    protected Briefnessor getBriefnessor() {
        return mBriefnessorRef.get();
    }

    public boolean isViewAttached() {
        return mViewRef != null && mViewRef.get() != null & mBriefnessorRef != null & mBriefnessorRef.get() != null;
    }

    public void dettachView() {
        if (mViewRef != null) {
            mViewRef.clear();
            mViewRef = null;
        }
        if (mBriefnessorRef != null) {
            mBriefnessorRef.clear();
            mBriefnessorRef = null;
        }
    }
}

BaseModel 持有ViewModel，并实现了IBaseView。

public abstract class BaseModel<VM extends IBaseViewModel> implements IBaseModel {
    protected VM viewModel;

    public BaseModel(VM viewModel) {
        this.viewModel = viewModel;
    }

    @Override
    public Context applicationContext() {
        return viewModel.applicationContext();
    }

    @Override
    public Activity context() {
        return viewModel.context();
    }
}

写的不好，请多多见谅，毕竟小学都没毕业😂
如果还有什么不明白的，代码直通车https://github.com/hacknife/Briefness/tree/master/example/src/main/java/com/hacknife/demo/mvvm