MVP理解與實踐

2019-11-09 14:03:56

字體：大中小

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MVP模式概念

在MVP模式里通常包含4個要素：

View:負責繪制UI元素、與用戶進行交互(在Android中體現為Activity); View interface:需要View實現的接口，View通過View interface與PResenter進行交互，降低耦合，方便進行單元測試; Model:負責存儲、檢索、操縱數據(有時也實現一個Model interface用來降低耦合);Presenter:作為View與Model交互的中間紐帶，處理與用戶交互的負責邏輯。

??在Android開發中，Activity并不是一個標準的MVC模式中的Controller，它的首要職責是加載應用的布局和初始化用戶界面，并接受并處理來自用戶的操作請求，進而作出響應。隨著界面及其邏輯的復雜度不斷提升，Activity類的職責不斷增加，以致變得龐大臃腫。 ??當我們將其中復雜的邏輯處理移至另外的一個類（Presneter）中時，Activity其實就是MVP模式中 View，它負責UI元素的初始化，建立UI元素與Presenter的關聯（Listener之類），同時自己也會處理一些簡單的邏輯（復雜的邏輯交由 Presenter處理）。

MVP與MVC模式對比

MVP模式：

View不直接與Model交互，而是通過與Presenter交互來與Model間接交互Presenter與View的交互是通過接口來進行的，更有利于添加單元測試通常View與Presenter是一對一的，但復雜的View可能綁定多個Presenter來處理邏輯

MVC模式：

View可以與Model直接交互Controller是基于行為的，并且可以被多個View共享

MVP項目代碼組織方式

項目含一個app src目錄，4個測試目錄：

測試目錄分別是androidTest（UI層測試）、androidTestMock（UI層測試mock數據支持）、test（業務層單元測試）、mock（業務層單元測試mock數據支持）。

src目錄

按照功能組織，功能內部分為xactivity、xcontract、xfragment、xpresenter四個類文件(x代表業務名稱)；按照類型組織，比如按照activity、adapter、fragment、contract、presenter進行劃分，不同的類文件分別放到不同的目錄中。

MVP具體應用實現

/** * mvp 中的 v */public interface IView { /** * 添加 presenter */ void addPresenter(ipresenter presenter); /** * 結束當前view */ void finish();}

/** * mvp中的P */public interface IPresenter { /** * 回調 * @return true,已經處理. */ boolean onActivityResult(int requestCode, int resultCode, Intent data); /** * 注冊廣播 */ String[] registerLocalReceivers(); /** * 接收到廣播 */ void onLocalReceive(Intent intent); /** * UI銷毀,釋放view */ void onDestroyView();}/** * 業務處理基類 */public abstract class AbsPresenter implements IPresenter { protected AppCompatActivity mActivity; protected Context mContext; protected LoaderManager mLoaderManager; public AbsPresenter(@NonNull IView view) { if (view instanceof AppCompatActivity) { initWithActivity((AppCompatActivity) view); } else if (view instanceof Fragment) { initWithFragment((Fragment) view); } else if (view instanceof ActivityInstrumentationTestCase2) { ActivityInstrumentationTestCase2 testCase = (ActivityInstrumentationTestCase2) view; mContext = testCase.getActivity(); mActivity = (AppCompatActivity) testCase.getActivity(); mLoaderManager = mActivity.getSupportLoaderManager(); } else { throw new RuntimeException("view must be instance of AppCompatActivity or Fragment."); } } private void initWithActivity(AppCompatActivity activity) { mActivity = activity; mContext = mActivity; mLoaderManager = mActivity.getSupportLoaderManager(); } private void initWithFragment(Fragment fragment) { mActivity = (AppCompatActivity) fragment.getActivity(); mContext = fragment.getContext(); mLoaderManager = fragment.getLoaderManager(); } @Override public boolean onActivityResult(int requestCode, int resultCode, Intent data) { return false; } @Override public String[] registerLocalReceivers() { return new String[0]; } @Override public void onLocalReceive(Intent intent) { } @Override @CallSuper public void onDestroyView() { mActivity = null; mContext = null; mLoaderManager = null; }}

MVP中的M也就是Model層一般和Bean實體會抽離出來，作為中間件接口調用，如ModelService Module

實現某個具體業務流程如下：

定義某個業務Presenter接口IXxPresenter extends IPresenter定義某個業務顯示View接口IXxView extends IView實現某個業務Presenter–XxPresenter(增刪查改) extends AbsPresenter implements IXxPresenter, LoaderManager.LoaderCallbacks<Cursor>private IXxView mView;private XxTask mXxTask;public XxPresenter(@NonNull IXxView view) { super(view); mView = view;}@Overridepublic Loader<Cursor> onCreateLoader(int id, Bundle args) {//返回一個new CursorLoader對象}@Overridepublic void onLoadFinished(Loader<Cursor> loader, Cursor data) {//完成對UI主界面的更新 if(mView != null) { mView.showXx(); }}@Overridepublic void onLoaderReset(Loader<Cursor> loader) {}@Overridepublic void queryXx() { mLoaderManager.destroyLoader(AppConst.LOADER_ID.XXX); mLoaderManager.initLoader(AppConst.LOADER_ID.XXX, null, this);}@Overridepublic void updateXx() { if (mXxTask == null || mXxTask.getStatus() != AsyncTask.Status.RUNNING) { mXxTask = new XxTask(); mXx.execute(); }}//deleteXx //saveXx(insert && update,根據是否有有效ID值判斷)private void destroyLoader() { mLoaderManager.destroyLoader(AppConst.LOADER_ID.XXX); mLoaderManager.destroyLoader(AppConst.LOADER_ID.YYY);}@Overridepublic void onDestroyView() { destroyLoader(); if (mXxTask != null) { mXxTask.cancel(true); mXxTask = null; } mView = null; super.onDestroyView();}private class XxTask extends AsyncTask<Void, Void, Boolean> { private xx; private xxx; XxTask() { //初始化成員變量 } @Override protected Boolean doInBackground(Void... params) { //返回類型自定義 } @Override protected void onPostExecute(Boolean res) { super.onPostExecute(res); if(mView != null) { mView.showXx(); } }}

Presenter實例化

/** * Presenter工廠,用于實例化相對的Presenter */public interface IPresenterFactory { /** * 返回Presenter實現類的實例 */ @Nullable IPresenter newPresenter(IView view, Class clazz);}/** * Presenter實例化工廠 */public class PresenterFactory implements IPresenterFactory { @Nullable @Override public IPresenter newPresenter(IView view, Class clazz) { final String className = clazz.getName(); IPresenter presenter = null; if (view instanceof IXxView && className.equals(IXxPresenter.class.getName())) { IXxView xxView = (IXxView) view; return new XxPresenter(xxView); } }}/** * app application */public class XxApplication extends ApplicationWrapper { @Override public void onCreate() { super.onCreate(); ...... // presenter初始化 Presenter.init(new PresenterFactory()); ...... }}

Presenter與Activity綁定，Activity實現View接口

/** * Activity基類 */public abstract class BaseActivity extends AppCompatActivity { protected Context mContext = this; protected ActionBar mActionBar; protected Toolbar mToolbar; protected TextView mTitleTv; protected ImageView mIconIv; private List<IPresenter> mPresenterList = new ArrayList<>(); private BroadcastReceiver mReceiver; @Override @CallSuper protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); mReceiver = new BroadcastReceiver() { @Override public void onReceive(Context context, Intent intent) { AppBarActivity.this.onLocalReceive(intent); } }; registerLocalReceiver(); } @Override @CallSuper protected void onDestroy() { unregisterLocalReceiver(); for (IPresenter presenter : mPresenterList) { presenter.onDestroyView(); } super.onDestroy(); } /** * 查找控件 */ @CallSuper protected void findWidget() { mToolbar = (Toolbar) findViewById(R.id.toolbar); mTitleTv = (TextView) findViewById(R.id.title_tv); mIconIv = (ImageView) findViewById(R.id.logo_iv); } /** * 顯示或隱藏標題圖標,由子類去實現 */ protected void showIcon(boolean show) { if (show) { mIconIv.setVisibility(View.VISIBLE); mTitleTv.setVisibility(View.GONE); } else { mIconIv.setVisibility(View.GONE); mTitleTv.setVisibility(View.VISIBLE); } } /** * 設置標題 */ public void setTitle(String title) { mTitleTv.setText(title); } /** * 設置actionBar的顯示和隱藏 */ public void setActionBarVisibility(int visibility) { mToolbar.setVisibility(visibility); } /** * 隱藏標題 */ public void hideAppBar() { if (mToolbar != null) { mToolbar.setVisibility(View.GONE); } } /** * 初始化控件 */ protected void initWidget() { if (mToolbar != null) { setSupportActionBar(mToolbar); mActionBar = getSupportActionBar(); if (mActionBar != null) { mActionBar.setDisplayShowTitleEnabled(false); mActionBar.setDisplayHomeAsUpEnabled(true); mActionBar.setHomeAsUpIndicator(R.drawable.icon_back); } } } protected void setListener() { } @CallSuper public void addPresenter(IPresenter presenter) { mPresenterList.add(presenter); } @Override public boolean onOptionsItemSelected(MenuItem item) { if (item.getItemId() == android.R.id.home) { onBackPressed(); return true; } else { return super.onOptionsItemSelected(item); } } @CallSuper protected void onLocalReceive(Intent intent) { for (IPresenter presenter : mPresenterList) { presenter.onLocalReceive(intent); } } @CallSuper protected String[] registerLocalReceivers() { ArrayList<String> allActionList = new ArrayList<>(); List<String> actionList; for (IPresenter presenter : mPresenterList) { actionList = Arrays.asList(presenter.registerLocalReceivers()); allActionList.addAll(actionList); } String[] actions = new String[allActionList.size()]; actions = allActionList.toArray(actions); return actions; } private void registerLocalReceiver() { LocalBroadcastManager localBroadcastManager = LocalBroadcastManager.getInstance(mContext); IntentFilter intentFilter = new IntentFilter(); String[] actions = registerLocalReceivers(); for (String action : actions) { intentFilter.addAction(action); } localBroadcastManager.registerReceiver(mReceiver, intentFilter); } private void unregisterLocalReceiver() { LocalBroadcastManager localBroadcastManager = LocalBroadcastManager.getInstance(mContext); localBroadcastManager.unregisterReceiver(mReceiver); }}XxActivity extends BaseActivity implements IXxView, IXxxView, ...private IXxPresenter mXxPresenter;@Overrideprotected void onCreate(Bundle savedInstanceState) { Presenter.bind(this, IXxPresenter.class, IXxxPresenter.class, ...); super.onCreate(savedInstanceState); //setContentView() findWidget(); initWidget(); setListener();}@Overridepublic void addPresenter(IPresenter presenter) { super.addPresenter(presenter); if (presenter instanceof IXxPresenter) { mXxPresenter = (IXxPresenter) presenter; }...}/** * 初始化控件 */@Overrideprotected void initWidget() { super.initWidget(); if(mXxPresenter != null) { mXxPresenter.queryXx();//查詢數據 }}@Overridepublic void showXx(params) {//傳遞數據//顯示數據到UI界面}

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