基本实现已经完成了，接下来就是封装了。

一、Acitvity的封装

我把Activity封装成了三层

1.MvvmActivity

public abstract class MvvmActivity<V extends ViewDataBinding, VM extends ViewModel> extends AppCompatActivity {

    /**
     * DataBinding
     */
    protected V mDataBinding;
    /**
     * ViewModel
     */
    protected VM mViewModel;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        initAAC();
    }

    /**
     * 获取视图ID
     *
     * @return 视图ID
     */
    protected abstract int getLayoutId();

    /**
     * 获取ViewModel
     *
     * @return ViewModel
     */
    protected abstract VM getViewModel();

    /**
     * 初始化 DataBinding 变量ID 和 变量实体类 Map
     *
     * @return DataBinding 变量SparseArray
     */
    protected abstract SparseArray<Object> getVariableSparseArray();

    /**
     * 初始化AAC组件
     */
    private void initAAC() {
        mDataBinding = DataBindingUtil.setContentView(this, getLayoutId());
        mViewModel = getViewModel();
        final SparseArray<Object> variableSA = getVariableSparseArray();
        if (variableSA != null && variableSA.size() > 0) {
            for (int i = 0; i < variableSA.size(); ++i) {
                final int variableId = variableSA.keyAt(i);
                final Object variableValue = variableSA.valueAt(i);
                mDataBinding.setVariable(variableId, variableValue);
            }
        }
        //让ViewModel拥有View的生命周期感应
        if (mViewModel != null) {
            getLifecycle().addObserver(mViewModel);
        }
    }

    /**
     * 工厂模式创建ViewModel
     *
     * @param cls     Activity Class
     * @param factory 工厂
     * @return ViewModel子类
     */
    public VM createViewModel(@NonNull Class<VM> cls, @NonNull ViewModelProvider.NewInstanceFactory factory) {
        return new ViewModelProvider(this, factory).get(cls);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        //销毁DataBinding
        if (mDataBinding != null) {
            mDataBinding.unbind();
        }
    }

}

第一层把databinding进行绑定和解绑，给ViewModel注册生命周期感知

2.MvvmActivity

public abstract class MvvmBaseActivity<V extends ViewDataBinding, VM extends ViewModel> extends MvvmActivity<V, VM> {

    /**
     * RxPermission (响应式权限申请框架)
     */
    protected RxPermissions mRxPermissions;
    /**
     * 页面跳转携带的数据Bundle
     */
    protected Bundle mBundle;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        initParam();
        initData();
        initAction();
        initObserver();
    }

    /**
     * 初始化参数
     */
    protected void initParam() {
        if (getIntent() != null) {
            mBundle = getIntent().getExtras();
        }
    }

    /**
     * 初始化数据
     */
    protected void initData() {
        //创建RxPermission对象
        if (this.getClass().isAnnotationPresent(NeedPermissions.class)) {
            mRxPermissions = new RxPermissions(this);
        }
        //注册EventBus
        if (this.getClass().isAnnotationPresent(BindEventBus.class)
                && !EventBus.getDefault().isRegistered(this)) {
            EventBus.getDefault().register(this);
        }

    }

    /**
     * 初始化事件
     */
    protected void initAction() {
    }

    /**
     * 初始化 LiveData Observer
     */
    protected void initObserver() {
        //显示加载中提示对话框
        mViewModel.getUiChangeLiveDataManager().getShowLoadingDialogEvent().observe(this, s -> {
            LoadingDialog.getInstance()
                    .setHintText(s)
                    .show(this);
        });
        //隐藏加载中提示对话框
        mViewModel.getUiChangeLiveDataManager().getHideLoadingDialogEvent().observe(this, o -> {
            LoadingDialog.getInstance().hide();
        });
        //切换Activity
        mViewModel.getUiChangeLiveDataManager().getStartActivityEvent().observe(this, paramSA -> {
            final Class<?> cls = (Class<?>) paramSA.get(BaseViewModel.ParamConstant.CLASS);
            final Bundle bundle = (Bundle) paramSA.get(BaseViewModel.ParamConstant.BUNDLE);
            final Integer requestCode = (Integer) paramSA.get(BaseViewModel.ParamConstant.REQUEST_CODE);

            if (requestCode == null) {
                startActivity(cls, bundle);
            } else {
                startActivityForResult(cls, bundle, requestCode);
            }
        });
        //关闭销毁Activity
        mViewModel.getUiChangeLiveDataManager().getFinishEvent().observe(this, o -> {
            finish();
        });
    }

    /**
     * 通过Class跳转界面
     **/
    public void startActivity(Class<?> cls) {
        startActivity(cls, null);
    }

    /**
     * 含有Bundle通过Class跳转界面
     **/
    public void startActivity(Class<?> cls, Bundle bundle) {
        Intent intent = new Intent();
        intent.setClass(this, cls);
        if (bundle != null) {
            intent.putExtras(bundle);
        }
        startActivity(intent);
    }

    /**
     * 通过Class跳转界面
     **/
    public void startActivityForResult(Class<?> cls, int requestCode) {
        startActivityForResult(cls, null, requestCode);
    }

    /**
     * 含有Bundle通过Class跳转界面
     **/
    public void startActivityForResult(Class<?> cls, Bundle bundle, int requestCode) {
        Intent intent = new Intent();
        intent.setClass(this, cls);
        if (bundle != null) {
            intent.putExtras(bundle);
        }
        startActivityForResult(intent, requestCode);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        //销毁加载中Dialog
        LoadingDialog.getInstance().destory();
        //销毁权限申请框架
        mRxPermissions = null;
        //清空Disposable
        clearDisposable();
        //解注册EventBus
        if (this.getClass().isAnnotationPresent(BindEventBus.class)
                && EventBus.getDefault().isRegistered(this)) {
            EventBus.getDefault().unregister(this);
        }
    }

}

第二层封装了一些通用的方法和一些必须框架的绑定和解绑

3.MvvmBaseActivity

public abstract class AppBaseActivity<V extends ViewDataBinding, VM extends ViewModel> extends MvvmBaseActivity<V, VM> {

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        LogUtil.d("页面", this.getClass().getSimpleName());
    }

    @Override
    protected void onStart() {
        super.onStart();
        initStatusBar();
    }

    /**
     * 初始化数据
     */
    @Override
    protected void initData() {
        super.initData();
        //Activity默认背景为白色
        getContentView().setBackgroundResource(R.color._FFFFFF);
        //设置状态栏高度
        if (!isSetCustomStatusBarHeight()) {
            @IdRes final int id = ResourceUtil.getResId("rl_layout_title_bar", R.id.class);
            if (id != -1) {
                final View view = findViewById(id);
                if (view != null) {
                    view.setPadding(0, StatusBarUtil.getStatusBarHeight(this), 0, 0);
                }
            }
        }
    }

    /**
     * 初始化状态栏
     */
    private void initStatusBar() {
        //设置默认状态栏背景颜色 为透明色
        StatusBarUtil.setStatusBarColor(this, R.color._00000000);
        //设置默认状态栏字体颜色 为浅色
        StatusBarUtil.setStatusBarContentColor(this, isSetStatusBarContentDark());
    }

    /**
     * 是否自定义设置状态栏高度
     *
     * @return true 自定义设置  false 默认设置
     */
    protected boolean isSetCustomStatusBarHeight() {
        return false;
    }

    /**
     * 是否设置状态栏内容颜色为深色
     *
     * @return true 深色  false 浅色
     */
    protected boolean isSetStatusBarContentDark() {
        return false;
    }


    /**
     * 连续双击退出应用
     */
    protected boolean mExitApp;

    /**
     * 指定间隔时间内 按下两次返回键退出App
     */
    public void doubleDownExitApp() {
        if (mExitApp) {
            //关闭所有的Activity
            ActivityUtils.finishAllActivities();
        } else {
            mExitApp = true;
            ToastUtils.showShort("再按一次退出应用");
            //超过两秒没有再次点击，则不退出App
            new Handler().postDelayed(() -> mExitApp = false, 2000);
        }
    }

}

第三层封装了一些沉浸式状态栏和双击退出的一些方法
以上利用泛型限制了数据类型，利用了抽象方法让子类实现变化的部分。

二、改造后的DemoActivity

public class DemoActivity extends AppBaseActivity<ActivityDemoBinding, AClass> {

    @Override
    protected int getLayoutId() {
        return R.layout.activity_demo;
    }

    @Override
    protected AClass getViewModel() {
        return new ViewModelProvider(this, new ViewModelProvider.NewInstanceFactory()).get(AClass.class);
    }

    @Override
    protected SparseArray<Object> getVariableSparseArray() {
        SparseArray<Object> variableSA = new SparseArray<>();
        variableSA.put(aClass, mViewModel);
        return variableSA;
    }
}