android輸入法架構解析

簡介：
前陣子接手維護了一個密碼鍵盤的項目，之前還沒有接觸過android輸入法這塊的知識點，所以在熟悉項目的同時將android系統輸入法實現框架整理了一遍，記錄在此.整個輸入法架構可以簡單劃分為主要三塊：

1.android輸入法管理服務InputMethodManagerService（IMMS）
2.android輸入法管理InputMethodManager(IMM)與當前輸入控件（EditText）
3.輸入法IME
簡要示意圖如下：

幾個主要類關系圖如下：

以下將按照如下流程分別進行介紹：
1.輸入法管理服務InputMethodManagerService（IMMS）簡介
2.輸入法管理InputMethodManager（IMM）簡介
3.輸入法服務InputMethodService簡介
4.從edittext點擊到輸入法界面顯示過程
5.輸入法字符傳遞到edittext過程

1.輸入法管理服務InputMethodManagerService簡介

IMMS主要管理輸入法，通過接收IMM的請求拉起或者隱藏輸入法，保持輸入法與IMM的連接，系統服務的啟動在systemserver中，輸入法管理是在startOtherServices中：

if (mFactoryTestMode != FactoryTest.FACTORY_TEST_LOW_LEVEL) {mSystemServiceManager.startService(InputMethodManagerService.Lifecycle.class);......}

進入到InputMethodManagerService中主要進行初始化操作，比如當前安裝的輸入法列表，設置默認輸入法，運行時序圖如下：

這里獲取默認輸入法列表和設置默認輸入法的操作都在初始化方法中完成：

public InputMethodManagerService(Context context) {mIPackageManager = AppGlobals.getPackageManager();mContext = context;mRes = context.getResources();mHandler = new Handler(this);// 這里后續會用來注冊幾個數據字段的監聽mSettingsObserver = new SettingsObserver(mHandler);mIWindowManager = IWindowManager.Stub.asInterface(ServiceManager.getService(Context.WINDOW_SERVICE));mWindowManagerInternal = LocalServices.getService(WindowManagerInternal.class);mCaller = new HandlerCaller(context, null, new HandlerCaller.Callback() {@Overridepublic void executeMessage(Message msg) {handleMessage(msg);}}, true /*asyncHandler*/);mAppOpsManager = mContext.getSystemService(AppOpsManager.class);mUserManager = mContext.getSystemService(UserManager.class);mHardKeyboardListener = new HardKeyboardListener();mHasFeature = context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_INPUT_METHODS);//獲取默認的系統設置mSlotIme = mContext.getString(com.android.internal.R.string.status_bar_ime);mHardKeyboardBehavior = mContext.getResources().getInteger(com.android.internal.R.integer.config_externalHardKeyboardBehavior);//初始化通知Bundle extras = new Bundle();extras.putBoolean(Notification.EXTRA_ALLOW_DURING_SETUP, true);mImeSwitcherNotification = new Notification.Builder(mContext).setSmallIcon(com.android.internal.R.drawable.ic_notification_ime_default).setWhen(0).setOngoing(true).addExtras(extras).setCategory(Notification.CATEGORY_SYSTEM).setColor(com.android.internal.R.color.system_notification_accent_color);Intent intent = new Intent(Settings.ACTION_SHOW_INPUT_METHOD_PICKER);mImeSwitchPendingIntent = PendingIntent.getBroadcast(mContext, 0, intent, 0);mShowOngoingImeSwitcherForPhones = false;//注冊用戶添加移除，從備份中恢復系統設置廣播final IntentFilter broadcastFilter = new IntentFilter();broadcastFilter.addAction(Intent.ACTION_CLOSE_SYSTEM_DIALOGS);broadcastFilter.addAction(Intent.ACTION_USER_ADDED);broadcastFilter.addAction(Intent.ACTION_USER_REMOVED);broadcastFilter.addAction(Intent.ACTION_SETTING_RESTORED);mContext.registerReceiver(new ImmsBroadcastReceiver(), broadcastFilter);mNotificationShown = false;int userId = 0;try {userId = ActivityManagerNative.getDefault().getCurrentUser().id;} catch (RemoteException e) {Slog.w(TAG, "Couldn't get current user ID; guessing it's 0", e);}//注冊app相關操作廣播，包括安裝卸載清除數據改變停止等mMyPackageMonitor.register(mContext, null, UserHandle.ALL, true);//初始化mSettings，后續用來存放和獲取一些InputMethod設置相關內容mSettings = new InputMethodSettings(mRes, context.getContentResolver(), mMethodMap, mMethodList, userId, !mSystemReady);//將從usermanager獲取的ProfileIds設置到mSettings中updateCurrentProfileIds();//InputMethodFileManager用來緩存用戶相關狀態mFileManager = new InputMethodFileManager(mMethodMap, userId);synchronized (mMethodMap) {mSwitchingController = InputMethodSubtypeSwitchingController.createInstanceLocked(mSettings, context);}//獲取系統默認設置輸入法名稱final String defaultImiId = mSettings.getSelectedInputMethod();if (DEBUG) {Slog.d(TAG, "Initial default ime = " + defaultImiId);}mImeSelectedOnBoot = !TextUtils.isEmpty(defaultImiId);synchronized (mMethodMap) {//解析所有安裝的輸入法，將其轉換為InputMethodInfo添加到列表mMethodList和mMethodMap中，并且處理默認輸入法相關，比如設置和重設新的默認輸入法buildInputMethodListLocked(!mImeSelectedOnBoot /* resetDefaultEnabledIme */);}//首次啟動會將所有的輸入法id以":"隔離開組成字符串寫入到系統數據庫ENABLED_INPUT_METHODS字段中mSettings.enableAllIMEsIfThereIsNoEnabledIME();if (!mImeSelectedOnBoot) {Slog.w(TAG, "No IME selected. Choose the most applicable IME.");synchronized (mMethodMap) {//如果還沒有設置默認輸入法就去設置，將獲取到的可用輸入法列表的第一個設置為默認輸入法resetDefaultImeLocked(context);}}synchronized (mMethodMap) {//注冊系統數據庫中部分跟輸入法相關字段改動的監聽mSettingsObserver.registerContentObserverLocked(userId);//使能當前安裝的所有輸入法，設置默認輸入法，發送輸入法變化通知，設置虛擬鍵盤是否要與實體鍵盤共存updateFromSettingsLocked(true);}//監聽ACTION_LOCALE_CHANGED廣播以便能夠在語言區域發生改變時候能夠及時對默認輸入法做出調整final IntentFilter filter = new IntentFilter();filter.addAction(Intent.ACTION_LOCALE_CHANGED);mContext.registerReceiver(new BroadcastReceiver() {@Overridepublic void onReceive(Context context, Intent intent) {synchronized(mMethodMap) {resetStateIfCurrentLocaleChangedLocked();}}}, filter);}

這里可以看到，在初始化方法中進行的操作，可以概括為如下幾點：

一些全局變量初始化，包括mIPackageManager/mIWindowManager/mSettings/mFileManager等。

注冊廣播監聽器，監聽包括應用安裝卸載改變，位置變更在內的廣播

獲取當前系統安裝的所有輸入法，并且設置默認輸入法。

初始化完成后，會調用onBootPhase方法：

@Overridepublic void onBootPhase(int phase) {// Called on ActivityManager thread.// TODO: Dispatch this to a worker thread as needed.if (phase == SystemService.PHASE_ACTIVITY_MANAGER_READY) {StatusBarManagerService statusBarService = (StatusBarManagerService) ServiceManager.getService(Context.STATUS_BAR_SERVICE);mService.systemRunning(statusBarService);}}

這里詳細講下systemRunning：

public void systemRunning(StatusBarManagerService statusBar) {synchronized (mMethodMap) {if (DEBUG) {Slog.d(TAG, "--- systemReady");}if (!mSystemReady) {mSystemReady = true;final int currentUserId = mSettings.getCurrentUserId();mSettings.switchCurrentUser(currentUserId,!mUserManager.isUserUnlockingOrUnlocked(currentUserId));mKeyguardManager = mContext.getSystemService(KeyguardManager.class);mNotificationManager = mContext.getSystemService(NotificationManager.class);mStatusBar = statusBar;if (mStatusBar != null) {mStatusBar.setIconVisibility(mSlotIme, false);}updateSystemUiLocked(mCurToken, mImeWindowVis, mBackDisposition);mShowOngoingImeSwitcherForPhones = mRes.getBoolean(com.android.internal.R.bool.show_ongoing_ime_switcher);if (mShowOngoingImeSwitcherForPhones) {mWindowManagerInternal.setOnHardKeyboardStatusChangeListener(mHardKeyboardListener);}buildInputMethodListLocked(!mImeSelectedOnBoot /* resetDefaultEnabledIme */);if (!mImeSelectedOnBoot) {Slog.w(TAG, "Reset the default IME as \"Resource\" is ready here.");resetStateIfCurrentLocaleChangedLocked();InputMethodUtils.setNonSelectedSystemImesDisabledUntilUsed(mIPackageManager,mSettings.getEnabledInputMethodListLocked(),mSettings.getCurrentUserId(), mContext.getBasePackageName());}mLastSystemLocales = mRes.getConfiguration().getLocales();try {//連接默認輸入法的服務startInputInnerLocked();} catch (RuntimeException e) {Slog.w(TAG, "Unexpected exception", e);}}}}

systemRunning中還會繼續進行一遍初始化方法中進行過的，獲取當前所有安裝的輸入法然會設置默認輸入法的操作，更重要的是，在這里會與默認輸入法的服務進行連接

InputBindResult startInputInnerLocked() {if (mCurMethodId == null) {return mNoBinding;}if (!mSystemReady) {// If the system is not yet ready, we shouldn't be running third// party code.return new InputBindResult(null, null, mCurMethodId, mCurSeq,mCurUserActionNotificationSequenceNumber);}InputMethodInfo info = mMethodMap.get(mCurMethodId);if (info == null) {throw new IllegalArgumentException("Unknown id: " + mCurMethodId);}unbindCurrentMethodLocked(true);mCurIntent = new Intent(InputMethod.SERVICE_INTERFACE);mCurIntent.setComponent(info.getComponent());mCurIntent.putExtra(Intent.EXTRA_CLIENT_LABEL,com.android.internal.R.string.input_method_binding_label);mCurIntent.putExtra(Intent.EXTRA_CLIENT_INTENT, PendingIntent.getActivity(mContext, 0, new Intent(Settings.ACTION_INPUT_METHOD_SETTINGS), 0));if (bindCurrentInputMethodService(mCurIntent, this, Context.BIND_AUTO_CREATE| Context.BIND_NOT_VISIBLE | Context.BIND_NOT_FOREGROUND| Context.BIND_SHOWING_UI)) {mLastBindTime = SystemClock.uptimeMillis();mHaveConnection = true;mCurId = info.getId();mCurToken = new Binder();try {if (true || DEBUG) Slog.v(TAG, "Adding window token: " + mCurToken);//服務連接成功就將該服務添加到窗口管理token列表中mIWindowManager.addWindowToken(mCurToken,WindowManager.LayoutParams.TYPE_INPUT_METHOD);} catch (RemoteException e) {}return new InputBindResult(null, null, mCurId, mCurSeq,mCurUserActionNotificationSequenceNumber);} else {mCurIntent = null;Slog.w(TAG, "Failure connecting to input method service: "+ mCurIntent);}return null;}

輸入法管理服務暫時分析到這里，這里還有幾個類說明下其承擔的功能：
InputMethodInfo/InputMethodSubtype用來描述輸入法相關信息
InputMethodUtils$InputMethodSettings包含了所有與輸入法相關數據信息的讀取和寫入
InputMethodFileManager用于從subtypes.xml文件中讀取和寫入subtype信息
InputBindResult 用于記錄和描述一次成功的輸入法管理服務到輸入法的綁定
ClientState 用于記錄一次遠程連接到當前輸入法的客戶端描述
SessionState 用于記錄一次連接的會話狀態

總結：輸入法管理服務主要用于管理輸入法，默認輸入法的設置，輸入法應用的安裝卸載監聽等，輸入法界面的彈出，退出，持有當前輸入法和當前輸入法服務對象的連接。

2. 輸入法管理InputMethodManager（IMM）簡介

InputMethodManager存在應用進程中，在activity展示階段在就初始化了，其主要功能是管理當前焦點view，與IMMS通信完成輸入法的展示與隱藏，讓EditText與輸入法產生交互，之后輸入法發送的內容就可以直接通過從IMM傳入到輸入法的連接通道發送到edittext中。

/*** This is the root view of the overall window that currently has input* method focus.*/View mCurRootView;/*** This is the view that should currently be served by an input method,* regardless of the state of setting that up.*/View mServedView;/*** This is then next view that will be served by the input method, when* we get around to updating things.*/View mNextServedView;

IMM中的三個view，mCurRootView是當前activity的decorview，mServedView是當前正在被服務的輸入框edittext，mNextServedView是當前焦點處在的view，也就是很有可能成為下一個被服務的view。當view焦點發生改變時候就會通過focusIn與focusOut方法改變mNextServedView的值：

void focusInLocked(View view) {......對view合法性的檢測mNextServedView = view;scheduleCheckFocusLocked(view);}

如果對當前view有進一步的操作，就會將mNextServedView賦值給mServedView

private boolean checkFocusNoStartInput(boolean forceNewFocus) {......synchronized (mH) {......ic = mServedInputConnectionWrapper;mServedView = mNextServedView;mCurrentTextBoxAttribute = null;mCompletions = null;mServedConnecting = true;}......return true;}

checkFocusNoStartInput方法被調用的頻次非常高

變量mClien表示當前輸入法服務對象，由IMMS持有

final IInputMethodClient.Stub mClient = new IInputMethodClient.Stub() {}

其內部類ControlledInputConnectionWrapper，持有EditableInputConnection通過IMMS最終傳遞到了IputMethodService中，建立了edittext與輸入法之間的連接，輸入法中提交的字符通過這個通道的commitText方法展示到了edittext中。

3.輸入法服務InputMethodService簡介

InputMethodService是每個輸入法服務都必須要繼承的基類，結構如下：

通過IInputMethodWrapper類包裝后，在父類的onbind方法中返回給IMMS，

final public IBinder onBind(Intent intent) {if (mInputMethod == null) {mInputMethod = onCreateInputMethodInterface();}return new IInputMethodWrapper(this, mInputMethod);}

IMMS中綁定服務成功后獲得IInputMethodWrapper，

@Overridepublic void onServiceConnected(ComponentName name, IBinder service) {synchronized (mMethodMap) {if (mCurIntent != null && name.equals(mCurIntent.getComponent())) {mCurMethod = IInputMethod.Stub.asInterface(service);if (mCurToken == null) {Slog.w(TAG, "Service connected without a token!");unbindCurrentMethodLocked(false);return;}if (DEBUG) Slog.v(TAG, "Initiating attach with token: " + mCurToken);executeOrSendMessage(mCurMethod, mCaller.obtainMessageOO(MSG_ATTACH_TOKEN, mCurMethod, mCurToken));if (mCurClient != null) {clearClientSessionLocked(mCurClient);requestClientSessionLocked(mCurClient);}}}}

方法中mCurToken非空，在mCurMethod被賦值后，會繼續通過requestClientSessionLocked建立會話，會話建立完成后會將InputMethodService的子類InputMethodSessionImpl傳遞過來保存到ClientState中

void onSessionCreated(IInputMethod method, IInputMethodSession session,InputChannel channel) {synchronized (mMethodMap) {if (mCurMethod != null && method != null&& mCurMethod.asBinder() == method.asBinder()) {if (mCurClient != null) {clearClientSessionLocked(mCurClient);mCurClient.curSession = new SessionState(mCurClient,method, session, channel);InputBindResult res = attachNewInputLocked(true);if (res.method != null) {executeOrSendMessage(mCurClient.client, mCaller.obtainMessageOO(MSG_BIND_CLIENT, mCurClient.client, res));}return;}}}// Session abandoned. Close its associated input channel.channel.dispose();}

4.從edittext點擊到輸入法界面顯示過程

該過程分為兩步，點擊后與輸入法的bind與start過程，輸入法界面的展示過程。
點擊后的bind與start過程如下：

這里重點看下startInputInner與attachNewInputLocked，在這里會生成view的EditableInputConnection，作為參數傳入到ControlledInputConnectionWrapper中，ControlledInputConnectionWrapper作為參數傳入到IMMS中，最后通過startInput在將IInputMethodWrapper再次包裝成一個ControlledInputConnectionWrapper傳入到InputMethodService中賦值給mStartedInputConnection。這樣輸入法與EditText之間的就關聯上了。

boolean startInputInner(@InputMethodClient.StartInputReason final int startInputReason,IBinder windowGainingFocus, int controlFlags, int softInputMode,int windowFlags) {.....//得到view的連接EditableInputConnectionInputConnection ic = view.onCreateInputConnection(tba);......servedContext = new ControlledInputConnectionWrapper(icHandler != null ? icHandler.getLooper() : vh.getLooper(), ic, this);......final InputBindResult res = mService.startInputOrWindowGainedFocus(startInputReason, mClient, windowGainingFocus, controlFlags, softInputMode,windowFlags, tba, servedContext, missingMethodFlags);......} InputBindResult attachNewInputLocked(boolean initial) {......final SessionState session = mCurClient.curSession;if (initial) {executeOrSendMessage(session.method, mCaller.obtainMessageIOOO(MSG_START_INPUT, mCurInputContextMissingMethods, session, mCurInputContext,mCurAttribute));} else {executeOrSendMessage(session.method, mCaller.obtainMessageIOOO(MSG_RESTART_INPUT, mCurInputContextMissingMethods, session, mCurInputContext,mCurAttribute));}if (mShowRequested) {if (DEBUG) Slog.v(TAG, "Attach new input asks to show input");showCurrentInputLocked(getAppShowFlags(), null);}return new InputBindResult(session.session,(session.channel != null ? session.channel.dup() : null),mCurId, mCurSeq, mCurUserActionNotificationSequenceNumber);}

進入到InputMethodWrapper中，參數中的inputContext就是IMM中生成的ControlledInputConnectionWrapper

public void startInput(IInputContext inputContext,@InputConnectionInspector.MissingMethodFlags final int missingMethods,EditorInfo attribute) {mCaller.executeOrSendMessage(mCaller.obtainMessageIOO(DO_START_INPUT,missingMethods, inputContext, attribute));} case DO_START_INPUT: {SomeArgs args = (SomeArgs)msg.obj;int missingMethods = msg.arg1;IInputContext inputContext = (IInputContext)args.arg1;//再次封裝一層，這里不明白為何還要再封裝一層InputConnection ic = inputContext != null? new InputConnectionWrapper(mTarget, inputContext, missingMethods) : null;EditorInfo info = (EditorInfo)args.arg2;info.makeCompatible(mTargetSdkVersion);//ic賦值給了InputMethodService中的mStartedInputConnectioninputMethod.startInput(ic, info);args.recycle();return;} void doStartInput(InputConnection ic, EditorInfo attribute, boolean restarting) {if (!restarting) {doFinishInput();}mInputStarted = true;//連接建立mStartedInputConnection = ic;mInputEditorInfo = attribute;initialize();if (DEBUG) Log.v(TAG, "CALL: onStartInput");onStartInput(attribute, restarting);if (mWindowVisible) {if (mShowInputRequested) {if (DEBUG) Log.v(TAG, "CALL: onStartInputView");mInputViewStarted = true;onStartInputView(mInputEditorInfo, restarting);startExtractingText(true);} else if (mCandidatesVisibility == View.VISIBLE) {if (DEBUG) Log.v(TAG, "CALL: onStartCandidatesView");mCandidatesViewStarted = true;onStartCandidatesView(mInputEditorInfo, restarting);}}}

以上流程完成之后輸入法與edittext之間的連接建立，輸入法也已經綁定，可以展示界面進行輸入操作了。輸入法界面展示流程如下：

5.輸入法字符傳遞到edittext過程

輸入法字符發送到edittext的流程如下，這里以sendKeyChar為開頭，看過源碼中的拉丁輸入法是直接getCurrentInputConnection.commitText發送字符的

在BaseInputConnection中的replaceText方法中

private void replaceText(CharSequence text, int newCursorPosition,boolean composing) {final Editable content = getEditable();......content.replace(a, b, text);.....}

子類EditableInputConnection中的重載方法如下：

public Editable getEditable() {TextView tv = mTextView;if (tv != null) {return tv.getEditableText();}return null;}

所以最終文字的字符從輸入法發送到edittext是通過按索引替換來實現的。

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