1.客户端注册事件监听

我们知道当我们展示一个窗口时候,WindowManager会添加Decorview对应的IWindow到wms，这当中就会发生触摸事件的注册到InputManager

WindowManagerGlobal.java 
public void addView(View view, ViewGroup.LayoutParams params,
            Display display, Window parentWindow) {
        ...
        View panelParentView = null;
        ...
        root = new ViewRootImpl(view.getContext(), display);

        view.setLayoutParams(wparams);

        mViews.add(view);
        mRoots.add(root);
        mParams.add(wparams);
                ...
        root.setView(view, wparams, panelParentView);
        ...
    }

核心代码是mWindowSession.addToDisplay(..., mInputChannel);这是一个Binder会调用到Wms中，在wms给mInputChannel内部成员赋值，传回到app,然后WindowInputEventReceiver监听mInputChannel是否有值，有的话回调WindowInputEventReceiver

ViewRootImpl.java 
public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) {
        ...
        requestLayout();
        if ((mWindowAttributes.inputFeatures
                & WindowManager.LayoutParams.INPUT_FEATURE_NO_INPUT_CHANNEL) == 0) {
            mInputChannel = new InputChannel();
        }
        ...
          //addToDisplay发起Binder调用，wms端肯定也会有对应函数响应
        res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes,
                getHostVisibility(), mDisplay.getDisplayId(),
                mAttachInfo.mContentInsets, mAttachInfo.mStableInsets,
                mAttachInfo.mOutsets, mInputChannel);
        ...
        if (mInputChannel != null) {
            if (mInputQueueCallback != null) {
                mInputQueue = new InputQueue();
                mInputQueueCallback.onInputQueueCreated(mInputQueue);
            }
            mInputEventReceiver = new WindowInputEventReceiver(mInputChannel,
                    Looper.myLooper());
        }
      ...
    }

2.WMS服务端对应处理

wms端肯定也会有对应函数响应

Session.java
@Override
public int addToDisplay(IWindow window, int seq, WindowManager.LayoutParams attrs,
        int viewVisibility, int displayId, Rect outContentInsets, Rect outStableInsets,
        Rect outOutsets, InputChannel outInputChannel) {
    return mService.addWindow(this, window, seq, attrs, viewVisibility, displayId,
            outContentInsets, outStableInsets, outOutsets, outInputChannel);
}

WindowManagerService.java
public int addWindow(Session session, IWindow client, int seq,
        WindowManager.LayoutParams attrs, int viewVisibility, int displayId,
        Rect outContentInsets, Rect outStableInsets, Rect outOutsets,
        InputChannel outInputChannel) {
                ...
        //APP端每一个窗口对应一个wms端一个WindowState
        final WindowState win = new WindowState(this, session, client, token, parentWindow,
                appOp[0], seq, attrs, viewVisibility, session.mUid,
                session.mCanAddInternalSystemWindow);
        if  (openInputChannels) {
            win.openInputChannel(outInputChannel);
        }
        ...
}

这一步创建了一个socketpair，返回来俩个socket即 InputChannel[0]，inputChannels[1] ；inputChannels[1]给客户端传来的outInputChannel赋值，InputChannel[0]注册给InputManagerService，当有输入事件的时候InputManagerService发送事件给InputChannel[0]，然后app端在outInputChannel接受事件

WindowState.java
void openInputChannel(InputChannel outInputChannel) {
      String name = getName();
      InputChannel[] inputChannels = InputChannel.openInputChannelPair(name);
      mInputChannel = inputChannels[0];
      mClientChannel = inputChannels[1];
      mInputWindowHandle.inputChannel = inputChannels[0];
      if (outInputChannel != null) {
          //把app端传过来的outInputChannel赋值
          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);
  }

3总结

App添加窗口时会向wms请求，wms会创建一个socketpair的俩端一个端发给返回app，一端注册到InputManagerService中，当InputManagerService收到事件的时候就会通过socket夸进程通信，传回app端对应窗口