应用注册input事件

	应用如果要监听input的事件，那么肯定就存在一个注册监听input事件的过程，跟随着addView方法我们跟着走一下

frameworks/base/core/java/android/view/WindowManagerImpl.java

    @Override
    public void addView(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {
        applyDefaultToken(params);
        mGlobal.addView(view, params, mContext.getDisplay(), mParentWindow);
    }

frameworks/base/core/java/android/view/WindowManagerGlobal.java


    public void addView(View view, ViewGroup.LayoutParams params,
            Display display, Window parentWindow) {
   			// 省略无关代码，ViewRootImpl是view和window之间的一个沟通的桥梁，在ViewRootImpl构造函数中会做很多事，但目前我们不关心
            root = new ViewRootImpl(view.getContext(), display);
            view.setLayoutParams(wparams);

            mViews.add(view);
            mRoots.add(root);
            mParams.add(wparams);

            // do this last because it fires off messages to start doing things
            try {
            // 主要看这个方法，在这会创建InputChannel
                root.setView(view, wparams, panelParentView);
            } catch (RuntimeException e) {
                // BadTokenException or InvalidDisplayException, clean up.
                if (index >= 0) {
                    removeViewLocked(index, true);
                }
                throw e;
            }

frameworks/base/core/java/android/view/ViewRootImpl.java


public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) {
                if ((mWindowAttributes.inputFeatures
                        & WindowManager.LayoutParams.INPUT_FEATURE_NO_INPUT_CHANNEL) == 0) {
                        // 创建客户（应用）端的InputChannel对象,这里会创建socket进行service和client绑定
                    mInputChannel = new InputChannel();
                }
                mForceDecorViewVisibility = (mWindowAttributes.privateFlags
                        & PRIVATE_FLAG_FORCE_DECOR_VIEW_VISIBILITY) != 0;
                try {
                    mOrigWindowType = mWindowAttributes.type;
                    mAttachInfo.mRecomputeGlobalAttributes = true;
                    collectViewAttributes();
                    // 看这里将上面创建出来的客户端的InputChannel给到WindowSession，我们继续跟一下
                    res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes,
                            getHostVisibility(), mDisplay.getDisplayId(), mWinFrame,
                            mAttachInfo.mContentInsets, mAttachInfo.mStableInsets,
                            mAttachInfo.mOutsets, mAttachInfo.mDisplayCutout, mInputChannel);
                } catch (RemoteException e) {
                    mAdded = false;
                    mView = null;
                    mAttachInfo.mRootView = null;
                    mInputChannel = null;
                    mFallbackEventHandler.setView(null);
                    unscheduleTraversals();
                    setAccessibilityFocus(null, null);
                    throw new RuntimeException("Adding window failed", e);
                } finally {
                    if (restore) {
                        attrs.restore();
                    }
                }
}

frameworks/base/services/core/java/com/android/server/wm/Session.java

    @Override
    public int addToDisplay(IWindow window, int seq, WindowManager.LayoutParams attrs,
            int viewVisibility, int displayId, Rect outFrame, Rect outContentInsets,
            Rect outStableInsets, Rect outOutsets,
            DisplayCutout.ParcelableWrapper outDisplayCutout, InputChannel outInputChannel) {
            // 这里调到了windowManagerService
        return mService.addWindow(this, window, seq, attrs, viewVisibility, displayId, outFrame,
                outContentInsets, outStableInsets, outOutsets, outDisplayCutout, outInputChannel);
    }

frameworks/base/services/core/java/com/android/server/wm/WindowManagerService.java


public int addWindow(Session session, IWindow client, int seq,
            LayoutParams attrs, int viewVisibility, int displayId, Rect outFrame,
            Rect outContentInsets, Rect outStableInsets, Rect outOutsets,
            DisplayCutout.ParcelableWrapper outDisplayCutout, InputChannel outInputChannel) {

            final WindowState win = new WindowState(this, session, client, token, parentWindow,
                    appOp[0], seq, attrs, viewVisibility, session.mUid,
                    session.mCanAddInternalSystemWindow);
            if (win.mDeathRecipient == null) {
                // Client has apparently died, so there is no reason to
                // continue.
                Slog.w(TAG_WM, "Adding window client " + client.asBinder()
                        + " that is dead, aborting.");
                return WindowManagerGlobal.ADD_APP_EXITING;
            }

            if (win.getDisplayContent() == null) {
                Slog.w(TAG_WM, "Adding window to Display that has been removed.");
                return WindowManagerGlobal.ADD_INVALID_DISPLAY;
            }

            final boolean hasStatusBarServicePermission =
                    mContext.checkCallingOrSelfPermission(permission.STATUS_BAR_SERVICE)
                            == PackageManager.PERMISSION_GRANTED;
            mPolicy.adjustWindowParamsLw(win, win.mAttrs, hasStatusBarServicePermission);
            win.setShowToOwnerOnlyLocked(mPolicy.checkShowToOwnerOnly(attrs));

            res = mPolicy.prepareAddWindowLw(win, attrs);
            if (res != WindowManagerGlobal.ADD_OKAY) {
                return res;
            }

            final boolean openInputChannels = (outInputChannel != null
                    && (attrs.inputFeatures & INPUT_FEATURE_NO_INPUT_CHANNEL) == 0);
            if  (openInputChannels) {
            // 这个openInputChannel我们会做详细讲解
                win.openInputChannel(outInputChannel);
            }

frameworks/base/services/core/java/com/android/server/wm/WindowState.java

    void openInputChannel(InputChannel outInputChannel) {
        if (mInputChannel != null) {
            throw new IllegalStateException("Window already has an input channel.");
        }
        String name = getName();
        // openInputChannelPair 里边会创建一个socketpair，这是一个Unix socket，应用和inputDispacher分别会作为client和service端，往一个缓冲区去读写
        InputChannel[] inputChannels = InputChannel.openInputChannelPair(name);
        // 这里mInputChannel 和 mClientChannel 持有的分别是两个fd
        mInputChannel = inputChannels[0];
        mClientChannel = inputChannels[1];
        mInputWindowHandle.inputChannel = inputChannels[0];
        if (outInputChannel != null) {
            mClientChannel.transferTo(outInputChannel);
            mClientChannel.dispose();
            mClientChannel = null;
        } else {
            // If the window died visible, we setup a dummy input channel, so that taps
            // can still detected by input monitor channel, and we can relaunch the app.
            // Create dummy event receiver that simply reports all events as handled.
            mDeadWindowEventReceiver = new DeadWindowEventReceiver(mClientChannel);
        }
        mService.mInputManager.registerInputChannel(mInputChannel, mInputWindowHandle);
    }

frameworks/base/core/java/android/view/InputChannel.java

    public static InputChannel[] openInputChannelPair(String name) {
        if (name == null) {
            throw new IllegalArgumentException("name must not be null");
        }

        if (DEBUG) {
            Slog.d(TAG, "Opening input channel pair '" + name + "'");
        }
        return nativeOpenInputChannelPair(name);
    }

frameworks/base/core/jni/android_view_InputChannel.cpp

static jobjectArray android_view_InputChannel_nativeOpenInputChannelPair(JNIEnv* env,
        jclass clazz, jstring nameObj) {
    const char* nameChars = env->GetStringUTFChars(nameObj, NULL);
    std::string name = nameChars;
    env->ReleaseStringUTFChars(nameObj, nameChars);

    sp<InputChannel> serverChannel;
    sp<InputChannel> clientChannel;
    // 这里将 serverChannel、clientChannel给到openInputChannelPair进行赋值
    status_t result = InputChannel::openInputChannelPair(name, serverChannel, clientChannel);

    if (result) {
        String8 message;
        message.appendFormat("Could not open input channel pair.  status=%d", result);
        jniThrowRuntimeException(env, message.string());
        return NULL;
    }

frameworks/native/libs/input/InputTransport.cpp

status_t InputChannel::openInputChannelPair(const std::string& name,
        sp<InputChannel>& outServerChannel, sp<InputChannel>& outClientChannel) {
    int sockets[2];
    if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, sockets)) {
        status_t result = -errno;
        ALOGE("channel '%s' ~ Could not create socket pair.  errno=%d",
                name.c_str(), errno);
        outServerChannel.clear();
        outClientChannel.clear();
        return result;
    }

    int bufferSize = SOCKET_BUFFER_SIZE;
    这里去创建socketPair，分别有两个socket Fd， 这里两个socket FD,分别都可以往bufferSize申请的缓存区，写入和读取
    setsockopt(sockets[0], SOL_SOCKET, SO_SNDBUF, &bufferSize, sizeof(bufferSize));
    setsockopt(sockets[0], SOL_SOCKET, SO_RCVBUF, &bufferSize, sizeof(bufferSize));
    setsockopt(sockets[1], SOL_SOCKET, SO_SNDBUF, &bufferSize, sizeof(bufferSize));
    setsockopt(sockets[1], SOL_SOCKET, SO_RCVBUF, &bufferSize, sizeof(bufferSize));

    std::string serverChannelName = name;
    serverChannelName += " (server)";
    // 将sockets[0]给到ServerChannel
    outServerChannel = new InputChannel(serverChannelName, sockets[0]);

    std::string clientChannelName = name;
    clientChannelName += " (client)";
    // 将sockets[1]给到outClientChannel
    outClientChannel = new InputChannel(clientChannelName, sockets[1]);
    return OK;
}