MV* in Android
此部分完整代码在这里 （https://github.com/ivacf/archi），笔者在这里节选出部分代码方便对照演示。Android中的Activity的功能很类似于iOS中的UIViewController，都可以看做MVC中的Controller。在2010年左右经典的Android程序大概是这样的:
TextView mCounterText;
Button mCounterIncrementButton;
int mClicks = 0;
public void onCreate(Bundle b) {
super.onCreate(b);
mCounterText = (TextView) findViewById(R.id.tv_clicks);
mCounterIncrementButton = (Button) findViewById(R.id.btn_increment);
mCounterIncrementButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
mClicks++;
mCounterText.setText(""+mClicks);
}
});
}
后来2013年左右出现了ButterKnife（https://github.com/JakeWharton/butterknife）这样的基于注解的控件绑定框架，此时的代码看上去是这样的:
@Bind(R.id.tv_clicks) mCounterText;
@OnClick(R.id.btn_increment)
public void onSubmitClicked(View v) {
mClicks++;
mCounterText.setText("" + mClicks);
}
后来Google官方也推出了数据绑定的框架，从此MVVM模式在Android中也愈发流行:
<layout xmlns:android="http://schemas.android.com/apk/res/android">
<data>
<variable name="counter" type="com.example.Counter"/>
<variable name="counter" type="com.example.ClickHandler"/>
</data>
<LinearLayout
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@{counter.value}"/>
<Buttonandroid:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@{handlers.clickHandle}"/>
</LinearLayout>
</layout>
后来Anvil（https://github.com/zserge/anvil）这样的受React启发的组件式框架以及Jedux这样借鉴了Redux全局状态管理的框架也将Unidirectional 架构引入了Android开发的世界。
MVC
- 声明View中的组件对象或者Model对象
private Subscription subscription;
private RecyclerView reposRecycleView;
private Toolbar toolbar;
private EditText editTextUsername;
private ProgressBar progressBar;
private TextView infoTextView;
private ImageButton searchButton;
- 将组件与Activity中对象绑定，并且声明用户响应处理函数
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
progressBar = (ProgressBar) findViewById(R.id.progress);
infoTextView = (TextView) findViewById(R.id.text_info);
//Set up ToolBar
toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
//Set up RecyclerView
reposRecycleView = (RecyclerView) findViewById(R.id.repos_recycler_view);
setupRecyclerView(reposRecycleView);
// Set up search button
searchButton = (ImageButton) findViewById(R.id.button_search);
searchButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
loadGithubRepos(editTextUsername.getText().toString());
}
});
//Set up username EditText
editTextUsername = (EditText) findViewById(R.id.edit_text_username);
editTextUsername.addTextChangedListener(mHideShowButtonTextWatcher);
editTextUsername.setOnEditorActionListener(new TextView.OnEditorActionListener() {
@Override
public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {
if (actionId == EditorInfo.IME_ACTION_SEARCH) {
String username = editTextUsername.getText().toString();
if (username.length() > 0) loadGithubRepos(username);
return true;
}
return false;
}
});
- 用户输入之后的更新流程
progressBar.setVisibility(View.VISIBLE);
reposRecycleView.setVisibility(View.GONE);
infoTextView.setVisibility(View.GONE);
ArchiApplication application = ArchiApplication.get(this);
GithubService githubService = application.getGithubService();
subscription = githubService.publicRepositories(username)
.observeOn(AndroidSchedulers.mainThread())
.subscribeOn(application.defaultSubscribeScheduler())
.subscribe(new Subscriber<List<Repository>>() {
@Override
public void onCompleted() {
progressBar.setVisibility(View.GONE);
if (reposRecycleView.getAdapter().getItemCount() > 0) {
reposRecycleView.requestFocus();
hideSoftKeyboard();
reposRecycleView.setVisibility(View.VISIBLE);
} else {
infoTextView.setText(R.string.text_empty_repos);
infoTextView.setVisibility(View.VISIBLE);
}
}
@Override
public void onError(Throwable error) {
Log.e(TAG, "Error loading GitHub repos ", error);
progressBar.setVisibility(View.GONE);
if (error instanceof HttpException
&& ((HttpException) error).code() == 404) {
infoTextView.setText(R.string.error_username_not_found);
} else {
infoTextView.setText(R.string.error_loading_repos);
}
infoTextView.setVisibility(View.VISIBLE);
}
@Override
public void onNext(List<Repository> repositories) {
Log.i(TAG, "Repos loaded " + repositories);
RepositoryAdapter adapter =
(RepositoryAdapter) reposRecycleView.getAdapter();
adapter.setRepositories(repositories);
adapter.notifyDataSetChanged();
}
});
MVP
- 将Presenter与View绑定，并且将用户响应事件绑定到Presenter中
//Set up presenter
presenter = new MainPresenter();
presenter.attachView(this);
...
// Set up search button
searchButton = (ImageButton) findViewById(R.id.button_search);
searchButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
presenter.loadRepositories(editTextUsername.getText().toString());
}
});
- Presenter中调用Model更新数据，并且调用View中进行重新渲染
public void loadRepositories(String usernameEntered) {
String username = usernameEntered.trim();
if (username.isEmpty()) return;
mainMvpView.showProgressIndicator();
if (subscription != null) subscription.unsubscribe();
ArchiApplication application = ArchiApplication.get(mainMvpView.getContext());
GithubService githubService = application.getGithubService();
subscription = githubService.publicRepositories(username)
.observeOn(AndroidSchedulers.mainThread())
.subscribeOn(application.defaultSubscribeScheduler())
.subscribe(new Subscriber<List<Repository>>() {
@Override
public void onCompleted() {
Log.i(TAG, "Repos loaded " + repositories);
if (!repositories.isEmpty()) {
mainMvpView.showRepositories(repositories);
} else {
mainMvpView.showMessage(R.string.text_empty_repos);
}
}
@Override
public void onError(Throwable error) {
Log.e(TAG, "Error loading GitHub repos ", error);
if (isHttp404(error)) {
mainMvpView.showMessage(R.string.error_username_not_found);
} else {
mainMvpView.showMessage(R.string.error_loading_repos);
}
}
@Override
public void onNext(List<Repository> repositories) {
MainPresenter.this.repositories = repositories;
}
});
}
MVVM
- XML中声明数据绑定
<data>
<variable
name="viewModel"
type="uk.ivanc.archimvvm.viewmodel.MainViewModel"/>
</data>
...
<EditText
android:id="@+id/edit_text_username"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_toLeftOf="@id/button_search"
android:hint="@string/hit_username"
android:imeOptions="actionSearch"
android:inputType="text"
android:onEditorAction="@{viewModel.onSearchAction}"
android:textColor="@color/white"
android:theme="@style/LightEditText"
app:addTextChangedListener="@{viewModel.usernameEditTextWatcher}"/>
- View中绑定ViewModel
super.onCreate(savedInstanceState);
binding = DataBindingUtil.setContentView(this, R.layout.main_activity);
mainViewModel = new MainViewModel(this, this);
binding.setViewModel(mainViewModel);
setSupportActionBar(binding.toolbar);
setupRecyclerView(binding.reposRecyclerView);
- ViewModel中进行数据操作
public boolean onSearchAction(TextView view, int actionId, KeyEvent event) {
if (actionId == EditorInfo.IME_ACTION_SEARCH) {
String username = view.getText().toString();
if (username.length() > 0) loadGithubRepos(username);
return true;
}
return false;
}
public void onClickSearch(View view) {
loadGithubRepos(editTextUsernameValue);
}
public TextWatcher getUsernameEditTextWatcher() {
return new TextWatcher() {
@Override
public void beforeTextChanged(CharSequence charSequence, int start, int count, int after) {
}
@Override
public void onTextChanged(CharSequence charSequence, int start, int before, int count) {
editTextUsernameValue = charSequence.toString();
searchButtonVisibility.set(charSequence.length() > 0 ? View.VISIBLE : View.GONE);
}
@Override
public void afterTextChanged(Editable editable) {
}
};
}
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感谢作者：wxyyxc1992
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