多屏模式输入法可以正确切换屏幕展示原理剖析

背景

hi，粉丝朋友们：
近期有个学员问到了一个输入法相关问题。刚好梳理了一下输入法相关的在多屏模式的一个展示流程，这里做个记录，也相当于深入理解窗口相关的一篇干货blog。

如上面两幅图展示，输入法可以自由自在显示在双屏的任意屏幕，那么下面主要就是来解密输入到底如何做到的自由双屏展示。

分析思路

如果对输入相关业务不知道的话，那么就只能考虑从窗口层面入手，一般输入法都是其实是一个dialog，这个类是SoftInputWindow
一般输入法窗口显示到了其他屏幕，肯定相关的displayid是要变化的这里可以dumpsys window windows可以看出来
输入法窗口在副屏：

Window #1 Window{e79aca4 u0 InputMethod}:
    mDisplayId=2 rootTaskId=35 mSession=Session{d9973cd 1240:u0a10084} mClient=android.os.BinderProxy@e774f37
    mOwnerUid=10084 showForAllUsers=false package=com.android.inputmethod.latin appop=NONE
    mAttrs={(0,0)(fillxfill) gr=BOTTOM CENTER_VERTICAL sim={adjust=pan} ty=INPUT_METHOD fmt=TRANSPARENT wanim=0x1030056 receive insets ignoring z-order
      fl=NOT_FOCUSABLE LAYOUT_IN_SCREEN SPLIT_TOUCH HARDWARE_ACCELERATED DRAWS_SYSTEM_BAR_BACKGROUNDS
      pfl=USE_BLAST FIT_INSETS_CONTROLLED
      bhv=DEFAULT
      fitTypes=STATUS_BARS NAVIGATION_BARS
      fitSides=LEFT TOP RIGHT}
    Requested w=1120 h=2960 mLayoutSeq=64
    mIsImWindow=true mIsWallpaper=false mIsFloatingLayer=true
    mBaseLayer=131000 mSubLayer=0    mToken=WindowToken{8e22fba type=2011 android.os.Binder@8ee38e5}
    mViewVisibility=0x0 mHaveFrame=true mObscured=false
    mGivenContentInsets=[0,1759][0,0] mGivenVisibleInsets=[0,1759][0,0]
    mTouchableInsets=3 mGivenInsetsPending=false
    touchable region=SkRegion((0,1759,1440,2792))
    mFullConfiguration={1.0 310mcc260mnc [en_US] ldltr sw411dp w411dp h797dp 560dpi nrml long port finger qwerty/v/v dpad/v winConfig={ mBounds=Rect(0, 0 - 1440, 2960) mAppBounds=Rect(0, 0 - 1440, 2792) mMaxBounds=Rect(0, 0 - 1440, 2960) mDisplayRotation=ROTATION_0 mWindowingMode=fullscreen mDisplayWindowingMode=fullscreen mActivityType=undefined mAlwaysOnTop=undefined mRotation=ROTATION_0} s.49 fontWeightAdjustment=0}
    mLastReportedConfiguration={1.0 310mcc260mnc [en_US] ldltr sw411dp w411dp h797dp 560dpi nrml long port finger qwerty/v/v dpad/v winConfig={ mBounds=Rect(0, 0 - 1440, 2960) mAppBounds=Rect(0, 0 - 1440, 2792) mMaxBounds=Rect(0, 0 - 1440, 2960) mDisplayRotation=ROTATION_0 mWindowingMode=fullscreen mDisplayWindowingMode=fullscreen mActivityType=undefined mAlwaysOnTop=undefined mRotation=ROTATION_0} s.49 fontWeightAdjustment=0}
    mHasSurface=true isReadyForDisplay()=true mWindowRemovalAllowed=false
    Frames: parent=[0,0][1440,2960] display=[0,0][1440,2960] frame=[0,0][1440,2960] last=[0,0][1440,2960] insetsChanged=false
     surface=[0,0][0,0]
    ContainerAnimator:
      mLeash=Surface(name=Surface(name=e79aca4 InputMethod)/@0xd668dc2 - animation-leash of insets_animation)/@0xaeadaa0 mAnimationType=insets_animation
      Animation: com.android.server.wm.InsetsSourceProvider$ControlAdapter@c5c0659
        ControlAdapter mCapturedLeash=Surface(name=Surface(name=e79aca4 InputMethod)/@0xd668dc2 - animation-leash of insets_animation)/@0xaeadaa0
    WindowStateAnimator{ef4021e InputMethod}:
      mSurface=Surface(name=InputMethod)/@0x7be3aff
      Surface: shown=true layer=0 alpha=1.0 rect=(0.0,0.0)  transform=(1.0, 0.0, 0.0, 1.0)
      mDrawState=HAS_DRAWN       mLastHidden=false
      mEnterAnimationPending=false      mSystemDecorRect=[0,0][0,0]
    mForceSeamlesslyRotate=false seamlesslyRotate: pending=null    isOnScreen=true
    isVisible=true
    keepClearAreas: restricted=[], unrestricted=[]

输入法在主屏幕：

Window #7 Window{ee26d8d u0 InputMethod}:
    mDisplayId=0 rootTaskId=1 mSession=Session{d9973cd 1240:u0a10084} mClient=android.os.BinderProxy@7424e24
    mOwnerUid=10084 showForAllUsers=false package=com.android.inputmethod.latin appop=NONE
    mAttrs={(0,0)(fillxfill) gr=BOTTOM CENTER_VERTICAL sim={adjust=pan} ty=INPUT_METHOD fmt=TRANSPARENT wanim=0x1030056 receive insets ignoring z-order
      fl=NOT_FOCUSABLE LAYOUT_IN_SCREEN SPLIT_TOUCH HARDWARE_ACCELERATED DRAWS_SYSTEM_BAR_BACKGROUNDS
      pfl=USE_BLAST FIT_INSETS_CONTROLLED
      bhv=DEFAULT
      fitTypes=STATUS_BARS NAVIGATION_BARS
      fitSides=LEFT TOP RIGHT}
    Requested w=1440 h=2960 mLayoutSeq=162
    mIsImWindow=true mIsWallpaper=false mIsFloatingLayer=true
    mBaseLayer=131000 mSubLayer=0    mToken=WindowToken{ba8dd3a type=2011 android.os.Binder@4152c65}
    mViewVisibility=0x0 mHaveFrame=true mObscured=false
    mGivenContentInsets=[0,1675][0,0] mGivenVisibleInsets=[0,1675][0,0]
    mTouchableInsets=3 mGivenInsetsPending=false
    touchable region=SkRegion((0,1759,1440,2792))
    mFullConfiguration={1.0 310mcc260mnc [en_US] ldltr sw411dp w411dp h773dp 560dpi nrml long port finger qwerty/v/v dpad/v winConfig={ mBounds=Rect(0, 0 - 1440, 2960) mAppBounds=Rect(0, 0 - 1440, 2792) mMaxBounds=Rect(0, 0 - 1440, 2960) mDisplayRotation=ROTATION_0 mWindowingMode=fullscreen mDisplayWindowingMode=fullscreen mActivityType=undefined mAlwaysOnTop=undefined mRotation=ROTATION_0} s.24 fontWeightAdjustment=0}
    mLastReportedConfiguration={1.0 310mcc260mnc [en_US] ldltr sw411dp w411dp h773dp 560dpi nrml long port finger qwerty/v/v dpad/v winConfig={ mBounds=Rect(0, 0 - 1440, 2960) mAppBounds=Rect(0, 0 - 1440, 2792) mMaxBounds=Rect(0, 0 - 1440, 2960) mDisplayRotation=ROTATION_0 mWindowingMode=fullscreen mDisplayWindowingMode=fullscreen mActivityType=undefined mAlwaysOnTop=undefined mRotation=ROTATION_0} s.24 fontWeightAdjustment=0}
    mHasSurface=true isReadyForDisplay()=true mWindowRemovalAllowed=false
    Frames: parent=[0,84][1440,2960] display=[0,84][1440,2960] frame=[0,84][1440,2960] last=[0,84][1440,2960] insetsChanged=false
     surface=[0,0][0,0]
    ContainerAnimator:
      mLeash=Surface(name=Surface(name=ee26d8d InputMethod)/@0x1dbd753 - animation-leash of insets_animation)/@0xf16d3fd mAnimationType=insets_animation
      Animation: com.android.server.wm.InsetsSourceProvider$ControlAdapter@3fd88f2
        ControlAdapter mCapturedLeash=Surface(name=Surface(name=ee26d8d InputMethod)/@0x1dbd753 - animation-leash of insets_animation)/@0xf16d3fd
    WindowStateAnimator{fd93b43 InputMethod}:
       mAnimationIsEntrance=true      mSurface=Surface(name=InputMethod)/@0x85ed5c0
      Surface: shown=true layer=0 alpha=1.0 rect=(0.0,0.0)  transform=(1.0, 0.0, 0.0, 1.0)
      mDrawState=HAS_DRAWN       mLastHidden=false
      mEnterAnimationPending=false      mSystemDecorRect=[0,0][0,0]
    mForceSeamlesslyRotate=false seamlesslyRotate: pending=null    isOnScreen=true
    isVisible=true
    keepClearAreas: restricted=[], unrestricted=[]

明显看到了displayId是变化了，而且window对象不是一个

这里可以考虑在SoftInputWindow的构造方法中加入相关堆栈。

日志堆栈及源码

上一个屏幕的输入法移除

systemserver发起inputmethodservice的destory

bringDownServiceLocked:4744, ActiveServices (com.android.server.am)
bringDownServiceIfNeededLocked:4566, ActiveServices (com.android.server.am)
removeConnectionLocked:4923, ActiveServices (com.android.server.am)
unbindServiceLocked:3164, ActiveServices (com.android.server.am)
unbindService:12670, ActivityManagerService (com.android.server.am)
unbindService:2079, ContextImpl (android.app)
unbindMainConnection:450, InputMethodBindingController (com.android.server.inputmethod)
unbindCurrentMethod:353, InputMethodBindingController (com.android.server.inputmethod)
startInputUncheckedLocked:2843, InputMethodManagerService (com.android.server.inputmethod)
startInputOrWindowGainedFocusInternalLocked:4156, InputMethodManagerService (com.android.server.inputmethod)
startInputOrWindowGainedFocusInternal:3863, InputMethodManagerService (com.android.server.inputmethod)
startInputOrWindowGainedFocus:3816, InputMethodManagerService (com.android.server.inputmethod)
onTransact:402, IInputMethodManager$Stub (com.android.internal.view)
onTransact:1957, InputMethodManagerService (com.android.server.inputmethod)
execTransactInternal:1280, Binder (android.os)
execTransact:1244, Binder (android.os)

新的输入法service启动

realStartServiceLocked:4373, ActiveServices (com.android.server.am)
bringUpServiceLocked:4228, ActiveServices (com.android.server.am)
bindServiceLocked:2956, ActiveServices (com.android.server.am)
bindServiceInstance:12653, ActivityManagerService (com.android.server.am)
bindServiceInstance:12609, ActivityManagerService (com.android.server.am)
bindServiceCommon:2035, ContextImpl (android.app)
bindServiceAsUser:1974, ContextImpl (android.app)
bindCurrentInputMethodService:466, InputMethodBindingController (com.android.server.inputmethod)
bindCurrentInputMethodServiceMainConnection:479, InputMethodBindingController (com.android.server.inputmethod)
bindCurrentMethod:400, InputMethodBindingController (com.android.server.inputmethod)
startInputUncheckedLocked:2845, InputMethodManagerService (com.android.server.inputmethod)
startInputOrWindowGainedFocusInternalLocked:4156, InputMethodManagerService (com.android.server.inputmethod)
startInputOrWindowGainedFocusInternal:3863, InputMethodManagerService (com.android.server.inputmethod)
startInputOrWindowGainedFocus:3816, InputMethodManagerService (com.android.server.inputmethod)
onTransact:402, IInputMethodManager$Stub (com.android.internal.view)
onTransact:1957, InputMethodManagerService (com.android.server.inputmethod)
execTransactInternal:1280, Binder (android.os)
execTransact:1244, Binder (android.os)

这里可以看出主要是一个跨进程调用发起老的输入法service要stop，destory新的service要进行onCreate，这些堆栈都是在systemserver进程打出来的。
是谁发起跨进程startInputOrWindowGainedFocus方法呢？当然是app端啊，输入焦点EditText那个app

App端发起启动输入法

startInputInner:2379, InputMethodManager (android.view.inputmethod)
startInput:665, InputMethodManager$DelegateImpl (android.view.inputmethod)
startInputAsyncOnWindowFocusGain:733, InputMethodManager$DelegateImpl (android.view.inputmethod)
onPostWindowFocus:141, ImeFocusController (android.view)
handleWindowFocusChanged:3699, ViewRootImpl (android.view)
-$$Nest$mhandleWindowFocusChanged:-1, ViewRootImpl (android.view)
handleMessageImpl:5538, ViewRootImpl$ViewRootHandler (android.view)
handleMessage:5452, ViewRootImpl$ViewRootHandler (android.view)
dispatchMessage:106, Handler (android.os)
loopOnce:201, Looper (android.os)
loop:288, Looper (android.os)
main:7898, ActivityThread (android.app)
invoke:-1, Method (java.lang.reflect)
run:548, RuntimeInit$MethodAndArgsCaller (com.android.internal.os)
main:936, ZygoteInit (com.android.internal.os)

可以看到在app ViewRootImpl的handleWindowFocusChanged() 方法发起的操作

SoftInputWindow创建堆栈

LatinIME这个service的onCreate创建

<init>:135, SoftInputWindow (android.inputmethodservice)
onCreate:1515, InputMethodService (android.inputmethodservice)
onCreate:608, LatinIME (com.android.inputmethod.latin)
handleCreateService:4515, ActivityThread (android.app)
-$$Nest$mhandleCreateService:-1, ActivityThread (android.app)
handleMessage:2162, ActivityThread$H (android.app)
dispatchMessage:106, Handler (android.os)
loopOnce:201, Looper (android.os)
loop:288, Looper (android.os)
main:7898, ActivityThread (android.app)
invoke:-1, Method (java.lang.reflect)
run:548, RuntimeInit$MethodAndArgsCaller (com.android.internal.os)
main:936, ZygoteInit (com.android.internal.os)

创建SoftInputWindow的Display确定

相关创建SoftInputWindow代码关键的是这个context，看看这个context的创建流程

frameworks/base/core/java/android/app/ActivityThread.java

 @UnsupportedAppUsage
    private void handleCreateService(CreateServiceData data) {
//省略大部分
            ContextImpl context = ContextImpl.getImpl(service
                    .createServiceBaseContext(this, packageInfo));
                    }

调用到了createServiceBaseContext方法

frameworks/base/core/java/android/window/WindowProviderService.java

/** @hide */
@Override
public final Context createServiceBaseContext(ActivityThread mainThread,
        LoadedApk packageInfo) {
    final Context context = super.createServiceBaseContext(mainThread, packageInfo);
    final Display display = context.getSystemService(DisplayManager.class)
            .getDisplay(getInitialDisplayId());//这里是核心关键会创建display
    return context.createTokenContext(mWindowToken, display);
}

这里可以看到主要核心就是context.getSystemService(DisplayManager.class)
.getDisplay(getInitialDisplayId())获取一个display，这个display也就是最后决定输入在哪个屏幕的关键
这里主要通过getInitialDisplayId获取到合适的displayId

frameworks/base/core/java/android/inputmethodservice/AbstractInputMethodService.java

    /** @hide */
    @Override
    public final int getInitialDisplayId() {
        try {
        //这里主要调用到wms的getImeDisplayId
            return WindowManagerGlobal.getWindowManagerService().getImeDisplayId();
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

下面看看wms的getImeDisplayId
frameworks/base/services/core/java/com/android/server/wm/WindowManagerService.java

@Override
    public int getImeDisplayId() {
        synchronized (mGlobalLock) {
        //这里主要获取一下焦点的Display是谁
            final DisplayContent dc = mRoot.getTopFocusedDisplayContent();
            //这里有个getImePolicy获取，要等于DISPLAY_IME_POLICY_LOCAL才可以
            return dc.getImePolicy() == DISPLAY_IME_POLICY_LOCAL ? dc.getDisplayId()
                    : DEFAULT_DISPLAY;
        }
    }

那现在就清楚了，输入法显示在哪个Display，是最后调用到了wms的中的getImeDisplayId方法，这个方法主要就是获取当前谁是focused的display，然后把displayid传递回去

总结

整个多屏输入法的流程涉及到了3个进程

    ---->焦点app发起startInputAsyncOnWindowFocusGain
        ------>systemserver stop老的service，start新service
            -------->输入法进程创建新的service onCreate执行
                 ------->输入法创建带有display的context
                       -------->创建对于输入法窗口带有新的display

更多framework干货获取相关可以 私聊+v(androidframework007)
点击这里 https://mp.weixin.qq.com/s/Qv8zjgQ0CkalKmvi8tMGaw
视频：https://www.bilibili.com/video/BV1ah411d7Y3