Android之 MVC到MVVM架构发展和封装

一简介

1.1 软件架构发展趋势是解耦，即分离数据层和视图层，使得数据层专注于业务的数据和逻辑处理。从而提高代码的可读可编辑效率，提高团队协作能力，项目的生产能力，降低后期维护成本。

1.2 Android架构发展MVC -> MVP -> MVVM，目前最流程的MVVM，配合google的jetpack开发工具可以轻松实现MVVM架构

二 MVC

2.1 概念MVC (Model-View-Controller, 模型-视图-控制器)

模型层 (Model)：业务逻辑对应的数据模型，无View无关，而与业务相关；
视图层 (View)：一般使用XML或者Java对界面进行描述；
控制层 (Controllor)：在Android中通常指Activity和Fragment，或者由其控制的业务类

2.2 基类封装BaseActivity

title.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"android:id="@+id/rl_title_layout"android:layout_width="match_parent"android:layout_height="44dp"android:background="@color/white"><ImageViewandroid:id="@+id/iv_back"android:layout_width="wrap_content"android:layout_height="match_parent"android:paddingLeft="15dp"android:paddingRight="15dp"android:src="@mipmap/back" /><TextViewandroid:id="@+id/tv_head_title"style="@style/Font_title"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_centerInParent="true"android:gravity="center"android:includeFontPadding="false"android:singleLine="true" /><TextViewandroid:id="@+id/tv_right_text"style="@style/Font_title"android:layout_width="wrap_content"android:layout_height="match_parent"android:layout_alignParentRight="true"android:layout_centerVertical="true"android:layout_marginRight="10dp"android:gravity="center"android:includeFontPadding="false"android:paddingLeft="5dp"android:paddingRight="5dp"android:singleLine="true"android:textColor="@color/color_3e"android:textSize="15sp" /><ImageViewandroid:id="@+id/iv_right"android:layout_width="wrap_content"android:layout_height="match_parent"android:layout_alignParentRight="true"android:layout_centerVertical="true"android:layout_marginRight="10dp"android:gravity="center"android:paddingLeft="5dp"android:paddingRight="5dp" />
</RelativeLayout>

activity_base.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><include layout="@layout/title"/><FrameLayoutandroid:id="@+id/root_layout"android:layout_width="match_parent"android:layout_height="match_parent"/>
</LinearLayout>

BaseActivity.java

public abstract class BaseActivity extends AppCompatActivity {public Activity mContext;private RelativeLayout rlTitleLayout;private ImageView ivBack;private TextView tvHeadTitle;private TextView tvRightText;private ImageView ivRight;private FrameLayout rootLayout;@Overrideprotected void onCreate(@Nullable Bundle savedInstanceState) {super.onCreate(savedInstanceState);mContext = this;setContentView(R.layout.activity_base);initRootView();}private void initRootView() {rlTitleLayout = (RelativeLayout) findViewById(R.id.rl_title_layout);ivBack = (ImageView) findViewById(R.id.iv_back);tvHeadTitle = (TextView) findViewById(R.id.tv_head_title);tvRightText = (TextView) findViewById(R.id.tv_right_text);ivRight = (ImageView) findViewById(R.id.iv_right);rootLayout = (FrameLayout) findViewById(R.id.root_layout);ivBack.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {finish();}});rootLayout.addView(View.inflate(this, getLayoutResId(), null));initView();initData();}public void hideTitleLayout() {rlTitleLayout.setVisibility(View.GONE);}public void setTitleText(String text) {tvHeadTitle.setText(text);}public void setTitleText(int resId) {tvHeadTitle.setText(getResources().getText(resId));}public void setRightText(int resId, View.OnClickListener onClickListener) {tvRightText.setText(getResources().getText(resId));tvRightText.setOnClickListener(onClickListener);}public void setRightImage(int resId, View.OnClickListener onClickListener) {ivRight.setImageResource(resId);ivRight.setOnClickListener(onClickListener);}protected abstract int getLayoutResId();public abstract void initView();/*** 初始化数据*/public abstract void initData();
}

使用MainActivity.java

public class MainActivity extends BaseActivity implements View.OnClickListener {private FrameLayout flMainFragment;private LinearLayout llBottom;private LinearLayout llFirst;private ImageView ivFirst;private TextView tvFirst;private LinearLayout llTwo;private ImageView ivTwo;private TextView tvTwo;private LinearLayout llThree;private ImageView ivThree;private TextView tvThree;private FragmentTransaction transaction;private HomeFragment homeFragment;private CommunityFragment communityFragment;private MeFragment meFragment;@Overrideprotected int getLayoutResId() {return R.layout.activity_main;}@Overridepublic void initView() {//UltimateBarXUtils.setNoAppBar(this, true);hideTitleLayout();flMainFragment = (FrameLayout) findViewById(R.id.fl_main_fragment);llBottom = (LinearLayout) findViewById(R.id.ll_bottom);llFirst = (LinearLayout) findViewById(R.id.ll_first);ivFirst = (ImageView) findViewById(R.id.iv_first);tvFirst = (TextView) findViewById(R.id.tv_first);llTwo = (LinearLayout) findViewById(R.id.ll_two);ivTwo = (ImageView) findViewById(R.id.iv_two);tvTwo = (TextView) findViewById(R.id.tv_two);llThree = (LinearLayout) findViewById(R.id.ll_three);ivThree = (ImageView) findViewById(R.id.iv_three);tvThree = (TextView) findViewById(R.id.tv_three);}@Overridepublic void initData() {llFirst.setOnClickListener(this);llTwo.setOnClickListener(this);llThree.setOnClickListener(this);setTabSelection(1);}@Overridepublic void onClick(View view) {switch (view.getId()){case R.id.ll_first:setTabSelection(1);break;case R.id.ll_two:setTabSelection(2);break;case R.id.ll_three:setTabSelection(3);break;}}public void setTabSelection(int index) {transaction = getSupportFragmentManager().beginTransaction();hideFragments(transaction);resetBtn();switch (index) {case 1:if (homeFragment == null) {homeFragment = new HomeFragment();transaction.add(R.id.fl_main_fragment, homeFragment);}transaction.show(homeFragment);ivFirst.setImageResource(R.mipmap.tab1_se);tvFirst.setTextColor(getResources().getColor(R.color.color_blue_tab));break;case 2:if (communityFragment == null) {communityFragment = new CommunityFragment();transaction.add(R.id.fl_main_fragment, communityFragment);}transaction.show(communityFragment);ivTwo.setImageResource(R.mipmap.tab2_se);tvTwo.setTextColor(getResources().getColor(R.color.color_blue_tab));break;case 3:if (meFragment == null) {meFragment = new MeFragment();transaction.add(R.id.fl_main_fragment, meFragment);}transaction.show(meFragment);ivThree.setImageResource(R.mipmap.tab3_se);tvThree.setTextColor(getResources().getColor(R.color.color_blue_tab));break;}transaction.commitAllowingStateLoss();}private void resetBtn() {ivFirst.setImageResource(R.mipmap.tab1);ivTwo.setImageResource(R.mipmap.tab2);ivThree.setImageResource(R.mipmap.tab3);tvFirst.setTextColor(getResources().getColor(R.color.color_d8d8d8));tvTwo.setTextColor(getResources().getColor(R.color.color_d8d8d8));tvThree.setTextColor(getResources().getColor(R.color.color_d8d8d8));}private void hideFragments(FragmentTransaction transaction) {if (homeFragment != null) {transaction.hide(homeFragment);}if (communityFragment != null) {transaction.hide(communityFragment);}if (meFragment != null) {transaction.hide(meFragment);}}
}

2.3 基类封装BaseFragment

BaseFragment.java

public abstract class BaseFragment extends Fragment {public Activity mContext;@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);mContext = getActivity();}@Nullable@Overridepublic View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {View view = inflater.inflate(getLayoutId(), container, false);initView(view, savedInstanceState);initData();return view;}/*** Fragment数据的懒加载.*/protected boolean isVisible;@Overridepublic void setUserVisibleHint(boolean isVisibleToUser) {super.setUserVisibleHint(isVisibleToUser);if (getUserVisibleHint()) {isVisible = true;lazyLoad();} else {isVisible = false;}}protected void lazyLoad() {}public abstract int getLayoutId();public abstract void initView(View view, @Nullable Bundle savedInstanceState);/*** 初始化数据*/public abstract void initData();
}

fragment_home.xml

<?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"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><Viewandroid:id="@+id/view_statues"android:layout_width="match_parent"android:layout_height="0dp"/><RelativeLayoutandroid:layout_width="match_parent"android:layout_height="40dp"><TextViewstyle="@style/Font_black"android:layout_height="24dp"android:layout_centerVertical="true"android:layout_marginLeft="15dp"android:background="@drawable/shape_bg_color_f0eff5_30"android:gravity="center"android:paddingLeft="12dp"android:paddingRight="12dp"android:text="@string/home_property"android:textColor="@color/color_3e"android:textSize="15sp"android:textStyle="bold" /><ImageViewandroid:id="@+id/iv_search"android:layout_width="wrap_content"android:layout_height="match_parent"android:layout_alignParentRight="true"android:layout_marginRight="10dp"android:paddingLeft="5dp"android:paddingRight="5dp"android:src="@mipmap/home_search" /></RelativeLayout><androidx.core.widget.NestedScrollViewandroid:layout_width="match_parent"android:layout_height="match_parent"android:overScrollMode="never"android:scrollbars="none"><LinearLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content"android:orientation="vertical"></LinearLayout></androidx.core.widget.NestedScrollView>
</LinearLayout>

FragmentHome.java

public class HomeFragment extends BaseFragment{private View viewStatues;@Overridepublic int getLayoutId() {return R.layout.fragment_home;}@Overridepublic void initView(View view, @Nullable Bundle savedInstanceState) {viewStatues = (View) view.findViewById(R.id.view_statues);LinearLayout.LayoutParams layoutParams = (LinearLayout.LayoutParams) viewStatues.getLayoutParams();layoutParams.height = ScreenUtils.getStatusHeight(mContext);viewStatues.setLayoutParams(layoutParams);}@Overridepublic void initData() {}}

三 MVP

3.1 概念MVP (Model-View-Presenter)

模型层 (Model)：主要提供数据存取功能。
视图层 (View)：处理用户事件和视图。在Android中，可能是指Activity、Fragment或者View。
展示层 (Presenter)：负责通过Model存取书数据，连接View和Model，从Model中取出数据交给View。

3.2 封装基类

新建Presenter接口，Presenter.java

public interface Presenter<V extends BaseView> {void attachView(V view);void detachView();
}

新建Presenter基类BasePresenter.java

public class BasePresenter<V> implements IPresenter<V> {protected WeakReference<V> mViewRef; //View接口类型的弱引用/*** 建立关联* @param view*/public void attachView(V view){mViewRef=new WeakReference<V>(view);}/*** 解除关联*/public void detachView(){if (mViewRef!=null){mViewRef.clear();mViewRef=null;}}/*** 判断是否与View建立关联* @return*/public boolean isViewAttach(){return mViewRef != null && mViewRef.get() != null;}/*** 获取View* @return*/protected V getView(){return mViewRef.get();}}

新建Activity基类BaseActivity.java

public abstract class BaseActivity<T extends BasePresenter> extends AppCompatActivity {protected T mPresenter;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(getLayoutId());mPresenter=createPresneter();//关联viewif (mPresenter != null) {mPresenter.attachView(this);}init();}protected abstract T createPresneter();protected abstract void init();protected abstract int getLayoutId();@Overrideprotected void onDestroy() {super.onDestroy();//解除if (mPresenter != null) {mPresenter.detachView();}}
}

新建Fragment基类BaseFragment.java

public abstract class BaseFragment<T extends BasePresenter> extends Fragment {protected T mPresenter;@Nullable@Overridepublic View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {View mView = inflater.inflate(getLayoutId(), null);mPresenter = createPresneter();//关联viewif (mPresenter != null) {mPresenter.attachView(this);}init(mView);return mView;}protected abstract T createPresneter();/*** 初始化*/protected abstract void init(View view);/*** 布局ID** @return*/protected abstract int getLayoutId();@Overridepublic void onDestroy() {super.onDestroy();//解除if (mPresenter != null) {mPresenter.detachView();}}
}

3.3 实战，登录功能

新建登录视图操作接口，LoginView.java

public interface LoginView {String getUserName();String getPassWord();void toMainActivity();void showToast(String message);void finish();void showWaitDialog(String message);void hideWaitDialog();
}

新建数据操作接口，LoginModel.java

public interface LoginModel {void login();
}

新建桥梁连接Model合View， LoginPresenter.java

public class LoginPresenter extends BasePresenter<LoginView> implements LoginModel {@Overridepublic void login() {getView().showWaitDialog("正在登录...");String userName=getView().getUserName();String password=getView().getPassWord();String result="";if(StringUtils.isEmpty(userName)){result="用户名不能为空";getView().hideWaitDialog();getView().showToast(result);return;}if(StringUtils.isEmpty(password)){result="密码不能为空";getView().hideWaitDialog();getView().showToast(result);return;}RetrofitClient.getmInstance().postMapLogin(userName, password, new BaseSubscriber<HttpResponse<UserInfo>>() {@Overridepublic void onError(ExceptionHandle.ResponeThrowable e) {getView().hideWaitDialog();getView().showToast(e.message);}@Overridepublic void onNext(HttpResponse<UserInfo> userInfoHttpResponse) {if (userInfoHttpResponse.getStatus() == 1) {UserInfo userInfo = userInfoHttpResponse.getReturnX();getView().hideWaitDialog();getView().showToast("登录成功");getView().toMainActivity();getView().finish();} else {getView().hideWaitDialog();getView().showToast(userInfoHttpResponse.getInfo());}}});}
}

新建登录页面LoginActivity.java

public class LoginActivity extends BaseActivity implements LoginView {private MaterialEditText metName;private MaterialEditText metPassword;private Button btnLogin;LoginPresenter loginPresenter;@Overrideprotected int getLayoutId() {return R.layout.activity_login;}@Overrideprotected BasePresenter createPresneter() {loginPresenter = new LoginPresenter();return loginPresenter;}@Overrideprotected void init() {metName = (MaterialEditText) findViewById(R.id.met_name);metPassword = (MaterialEditText) findViewById(R.id.met_password);btnLogin = (Button) findViewById(R.id.btn_login);btnLogin.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {loginPresenter.login();}});}@Overridepublic String getUserName() {return  metName.getText().toString();}@Overridepublic String getPassWord() {return metPassword.getText().toString();}@Overridepublic void toMainActivity() {startActivity(new Intent(this,MainActivity.class));}@Overridepublic void showToast(String message) {ToastUtils.show(this,message);}@Overridepublic void finish() {}@Overridepublic void showWaitDialog(String message) {}@Overridepublic void hideWaitDialog() {}@Overrideprotected void onDestroy() {super.onDestroy();}
}

四 MVVM

4.1 概念MVVM（Model-View-ViewModel）

模型层 (Model)：负责从各种数据源中获取数据；
视图层 (View)：在 Android 中对应于 Activity 和 Fragment，用于展示给用户和处理用户交互，会驱动 ViewModel 从 Model 中获取数据；
ViewModel 层：用于将 Model 和 View 进行关联，我们可以在 View 中通过 ViewModel 从 Model 中获取数据；当获取到了数据之后，会通过自动绑定，比如 DataBinding，来将结果自动刷新到界面上。

4.2 Android中使用ViewModel + LiveData + DataBinding来快速实现MVVM架构的搭建，

ViewModel：① 绑定Activity ，② 页面布局绘制，③ 实现业务逻辑如登录功能
LiveData：① 可修改数据，② 数据观察
DataBinding：① 单向绑定，② 双向绑定

4.2 封装MVVM基类

在Model级build.gradle文件里开启dataBinding支持

android {compileSdk 32defaultConfig {applicationId "com.bob.diary"minSdk 21targetSdk 32versionCode 1versionName "1.0"testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"}dataBinding {enabled = true}
}

创建ViewModel基类，绑定Activity，BaseViewModel.java，BaseActivity.java

public abstract class BaseViewModel extends ViewModel implements DefaultLifecycleObserver {public Activity activity;public void setActivity(Activity activity) {this.activity = activity;}}

创建Activity基类，activity_base.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"><androidx.constraintlayout.widget.ConstraintLayoutandroid:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><include layout="@layout/layout_title_bar"android:id="@+id/layout_title_root"/><FrameLayoutandroid:id="@+id/fl_content_container"android:layout_width="0dp"android:layout_height="0dp"app:layout_constraintLeft_toLeftOf="parent"app:layout_constraintRight_toRightOf="parent"app:layout_constraintBottom_toBottomOf="parent"app:layout_constraintTop_toBottomOf="@id/layout_title_root"/></androidx.constraintlayout.widget.ConstraintLayout>
</layout>

public abstract class BaseActivity<VM extends BaseViewModel, DB extends ViewDataBinding>extends AppCompatActivity {public DB mDataBinding;protected VM mViewModel;protected ActivityBaseBinding activityBaseBinding;protected Activity mContext;@Overrideprotected void onCreate(@Nullable Bundle savedInstanceState) {mContext=this;super.onCreate(savedInstanceState);activityBaseBinding = DataBindingUtil.setContentView(this, R.layout.activity_base);mDataBinding = DataBindingUtil.inflate(getLayoutInflater(), getLayoutResId(),activityBaseBinding.flContentContainer, true);initViewModel();bindViewModel();if (mDataBinding != null) {mDataBinding.setLifecycleOwner(this);}//ViewModel订阅生命周期事件if (mViewModel != null) {getLifecycle().addObserver(mViewModel);mViewModel.setActivity(this);}init();}/*** 获取当前页面的布局资源ID** @return 布局资源ID*/protected abstract int getLayoutResId();/*** 初始化ViewModel*/protected abstract void initViewModel();/*** 绑定ViewModel*/protected abstract void bindViewModel();/*** 初始化*/protected abstract void init();/*** 设置标题*/public void setTitle(String title) {UltimateBarXUtils.setAppBar(this, true, R.color.white);ConstraintLayout layoutTitleRoot = findViewById(R.id.layout_title_root);layoutTitleRoot.setVisibility(View.VISIBLE);ImageView ivBack = findViewById(R.id.iv_back);TextView tvTitleMiddle = findViewById(R.id.tv_title_middle);ivBack.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {finish();}});tvTitleMiddle.setText(title);}}

使用，以登录为例，新建登录model，LoginModel.java

public class LoginModel extends BaseViewModel {//LiveData监听器public MutableLiveData<List<User>> userLiveData;public LoginModel() {userLiveData = new MutableLiveData<>();}//查询用户public void daoQueryAllUser() {//通知数据变化List<User> userList = DaoUserUtils.getInstance().daoQueryAllUser();userLiveData.postValue(userList);}
}

新建登录页面，activity_login.xml和LoginActivity.java

<?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></data><androidx.constraintlayout.widget.ConstraintLayoutandroid:layout_width="match_parent"android:layout_height="match_parent"android:background="@color/color_faf1ed"android:gravity="center_vertical"android:orientation="vertical"><LinearLayoutandroid:id="@+id/ll_login_layout"android:layout_width="match_parent"android:layout_height="0dp"android:gravity="center_vertical"android:orientation="vertical"app:layout_constraintBottom_toBottomOf="parent"app:layout_constraintBottom_toTopOf="@id/ll_policy_layout"app:layout_constraintLeft_toLeftOf="parent"app:layout_constraintRight_toRightOf="parent"app:layout_constraintTop_toTopOf="parent"><LinearLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content"android:layout_marginTop="-42dp"android:orientation="vertical"android:paddingLeft="@dimen/dp_32"android:paddingRight="@dimen/dp_32"><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@string/login_welcome_login"android:textColor="#E9756E"android:textSize="@dimen/sp_24"android:textStyle="bold" /><RelativeLayoutandroid:layout_width="match_parent"android:layout_height="@dimen/dp_40"android:layout_marginTop="@dimen/dp_30"><ImageViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_centerVertical="true"android:src="@mipmap/login_account"app:layout_constraintLeft_toLeftOf="parent"app:layout_constraintTop_toTopOf="parent" /><EditTextandroid:id="@+id/et_account"android:layout_width="match_parent"android:layout_height="match_parent"android:layout_marginLeft="@dimen/dp_30"android:background="@drawable/bg_orange_border_bottom"android:hint="@string/register_enter_account"android:maxLength="15"android:textColor="@color/color_e9756e"android:textColorHint="@color/color_e9756e"android:textSize="@dimen/sp_16" /></RelativeLayout><RelativeLayoutandroid:layout_width="match_parent"android:layout_height="@dimen/dp_40"android:layout_marginTop="@dimen/dp_30"><ImageViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_centerVertical="true"android:src="@mipmap/login_password"app:layout_constraintLeft_toLeftOf="parent"app:layout_constraintTop_toTopOf="parent" /><EditTextandroid:id="@+id/et_password"android:layout_width="match_parent"android:layout_height="match_parent"android:layout_marginLeft="@dimen/dp_30"android:background="@drawable/bg_orange_border_bottom"android:hint="@string/register_enter_password"android:inputType="textPassword"android:maxLength="15"android:textColor="@color/color_e9756e"android:textColorHint="@color/color_e9756e"android:textSize="@dimen/sp_16" /><ImageViewandroid:id="@+id/iv_see"android:layout_width="wrap_content"android:layout_height="match_parent"android:layout_alignParentRight="true"android:layout_centerVertical="true"android:paddingLeft="@dimen/dp_10"android:paddingRight="@dimen/dp_10"android:src="@mipmap/login_look_off" /></RelativeLayout><TextViewandroid:id="@+id/tv_register"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_gravity="right"android:padding="@dimen/dp_10"android:text="@string/login_register_account"android:textColor="#E9756E"android:textSize="@dimen/sp_12" /></LinearLayout><TextViewandroid:id="@+id/tv_confirm"android:layout_width="match_parent"android:layout_height="@dimen/dp_48"android:layout_marginLeft="@dimen/dp_15"android:layout_marginTop="@dimen/dp_70"android:layout_marginRight="@dimen/dp_15"android:background="@drawable/bg_orange_10"android:gravity="center"android:text="@string/login_to"android:textColor="@color/white"android:textSize="@dimen/sp_18"android:textStyle="bold"app:layout_constraintLeft_toLeftOf="parent"app:layout_constraintRight_toRightOf="parent"app:layout_constraintTop_toBottomOf="@id/ll_login_layout" /></LinearLayout><LinearLayoutandroid:id="@+id/ll_policy_layout"android:layout_width="0dp"android:layout_height="@dimen/dp_60"android:layout_marginLeft="@dimen/dp_15"android:layout_marginRight="@dimen/dp_15"android:orientation="horizontal"app:layout_constraintBottom_toBottomOf="parent"app:layout_constraintLeft_toLeftOf="parent"app:layout_constraintRight_toRightOf="parent"app:layout_constraintTop_toBottomOf="@id/ll_login_layout"><CheckBoxandroid:id="@+id/cb_check"android:layout_width="wrap_content"android:layout_height="wrap_content"android:button="@drawable/selector_checked"android:paddingTop="@dimen/dp_5"android:paddingBottom="@dimen/dp_5"android:paddingLeft="@dimen/dp_5"android:paddingRight="@dimen/dp_3"android:textColor="@color/color_3d3d3d"android:textSize="@dimen/sp_12" /><TextViewandroid:id="@+id/tv_policy"android:layout_width="wrap_content"android:layout_height="wrap_content"android:gravity="left|top"android:orientation="horizontal"android:text="@string/login_agreement_agree"android:textColor="@color/color_3d3d3d"android:textSize="@dimen/sp_12" /></LinearLayout></androidx.constraintlayout.widget.ConstraintLayout></layout>

public class LoginActivity extends BaseActivity<LoginModel, ActivityLoginBinding> {private boolean canSee;@Overrideprotected int getLayoutResId() {return R.layout.activity_login;}@Overrideprotected void initViewModel() {mViewModel = ViewModelProviders.of(this).get(LoginModel.class);}@Overrideprotected void bindViewModel() {//监听数据变化mViewModel.userLiveData.observe(this, new Observer<List<User>>() {@Overridepublic void onChanged(List<User> users) {User user = users.get(0);if (user == null) {ToastHelp.showToast("用户不存在");return;}startActivity(MainActivity.class);finish();}});}@Overrideprotected void init() {//登录点击事件mDataBinding.tvConfirm.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {String account = mDataBinding.etAccount.getText().toString();String password = mDataBinding.etPassword.getText().toString();if (TextUtils.isEmpty(account)) {ToastHelp.showToast(getResources().getString(R.string.register_enter_account));return;}if (TextUtils.isEmpty(password)) {ToastHelp.showToast(getResources().getString(R.string.register_enter_password));return;}mViewModel.daoQueryAllUser();}});}
}

4.3 BaseFragment封装

public abstract class BaseFragment<VM extends BaseViewModel, DB extends ViewDataBinding>extends Fragment {protected DB mDataBinding;protected VM mViewModel;private FragmentBaseBinding fragmentBaseBinding;protected Activity mContext;@Overridepublic void onCreate(@Nullable Bundle savedInstanceState) {super.onCreate(savedInstanceState);mContext=getActivity();initViewModel();// ViewModel订阅生命周期事件if (mViewModel != null) {getLifecycle().addObserver(mViewModel);} }@Nullable@Overridepublic View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {fragmentBaseBinding = DataBindingUtil.inflate(inflater, R.layout.fragment_base, container, false);mDataBinding = DataBindingUtil.inflate(inflater, getLayoutResId(),fragmentBaseBinding.flContentContainer, true);bindViewModel();mDataBinding.setLifecycleOwner(this);init();return fragmentBaseBinding.getRoot();}/*** 获取当前页面的布局资源ID** @return 布局资源ID*/protected abstract int getLayoutResId();/*** 初始化ViewModel*/protected abstract void initViewModel();/*** 绑定ViewModel*/protected abstract void bindViewModel();/*** 初始化*/protected abstract void init();protected boolean isVisible;/*** 在这里实现Fragment数据的缓加载.** @param isVisibleToUser*/@Overridepublic void setUserVisibleHint(boolean isVisibleToUser) {super.setUserVisibleHint(isVisibleToUser);if (getUserVisibleHint()) {isVisible = true;onVisible();} else {isVisible = false;onInvisible();}}protected void onVisible() {lazyLoad();}protected void lazyLoad() {}protected void onInvisible() {} 
}

BaseFragment的使用，以首页为例，新建HomeModel.java

public class HomeModel extends BaseViewModel {//LiveData监听器public MutableLiveData<List<User>> userLiveData;public LoginModel() {userLiveData = new MutableLiveData<>();}//查询用户public void daoQueryAllUser() {//通知数据变化List<User> userList = DaoUserUtils.getInstance().daoQueryAllUser();userLiveData.postValue(userList);}}

新建HomeFragment.java

public class HomeFragment extends BaseFragment<HomeModel, FragmentHomeBinding> implements View.OnClickListener {@Overrideprotected boolean isEventBus() {return true;}@Overrideprotected int getLayoutResId() {return R.layout.fragment_home;}@Overrideprotected void initViewModel() {mViewModel = ViewModelProviders.of(getActivity()).get(HomeModel.class);}@Overrideprotected void bindViewModel() {mDataBinding.setModel(mViewModel);}@Overrideprotected void init() {mViewModel.daoQueryAllUser();//监听数据变化mViewModel.userLiveData.observe(this, new Observer<List<User>>() {@Overridepublic void onChanged(List<User> users) {//加载用户信息if(users.size()>0){User user=users.get(0);GlideUtil.loadImageView(mContext,user.getAvatar(),mDataBinding.ivUser,R.mipmap.default_user);mDataBinding.tvNickName.setText(user.getName());}}});}
}

五总结，三种架构各自的特点

5.1 MVC特点

优势：简单易用，View接收用户操作，通过Controller去处理业务逻辑，并通过Model去获取/更新数据，然后Model层又将最新的数据传回View层进行页面展示。
劣势：由于XML布局能力弱，我们的View层的很多操作都是写在Activity/Fragment中，同时，Controller、Model层的代码也大都写在Activity/Fragment中，这就会导致一个问题，当业务逻辑比较复杂时，Activity/Fragment中的代码量会很大，其违背了类单一职责，不利于后续扩展及维护

5.2 MVP特点

View层接收用户操作，并通过持有的Presenter去处理业务逻辑，请求数据；接着Presenter层通过Model去获取数据，然后Model又将最新的数据传回Presenter层，Presenter层又持有View层的引用，进而将数据传给View层进行展示
与MCVC相比，View层与Model层不再交互，而是通过Presenter去进行联系
MVP是面向接口编程，Model/View/Presenter每层的职责分工明确，当业务复杂时，整个流程逻辑也是很清晰的
Presenter会被抽象成IPresenter接口及其一些列方法，每当实现一个功能时，都需要编写多个接口及其对应的方法，实现起来相对比较繁琐，而且每次有改动时，对应的接口方法也基本都会再去改动
View层与Presenter层相互持有，当View层关闭时，由于Presenter层不是生命周期感知的，可能会导致内存泄漏甚至是崩溃。如果你的项目中使用了RxJava，可以使用配合Rxjava自动解绑

5.3 MVVM特点

View层接收用户操作，并通过持有的ViewModel去处理业务逻辑，请求数据
ViewModel层通过Model去获取数据，然后Model又将最新的数据传回ViewModel层，这里ViewModel与Presenter所做的事基本是一样的
View层会通过观察者模式监听ViewModel层的数据变化，当有新数据时，View层能自动收到新数据并刷新界面，所以ViewModel不会也不能持有View层的引用。