performLaunchActivity的时候获取final int displayId = ActivityClient.getInstance().getDisplayId(r.token)，调用createDisplayContext创建context

@frameworks/base/core/java/android/app/ActivityThread.java
ActivityThread.performLaunchActivity()ContextImpl appContext = createBaseContextForActivity(r);final int displayId = ActivityClient.getInstance().getDisplayId(r.token);ContextImpl appContext = ContextImpl.createActivityContext(this, r.packageInfo, r.activityInfo, r.token, displayId, r.overrideConfig);for (int id : dm.getDisplayIds()) {isplay display = dm.getCompatibleDisplay(id, appContext.getResources());appContext = (ContextImpl) appContext.createDisplayContext(display);
@frameworks/base/core/java/android/app/ContextImpl.javaContextImpl context = new ContextImpl(null, mainThread, packageInfo, ContextParams.EMPTY, attributionTag, null, activityInfo.splitName, activityToken, null, 0, classLoader, null);context.mDisplay = resourcesManager.getAdjustedDisplay(displayId, context.getResources());  //记录Display
@frameworks/base/core/java/android/app/Activity.javaactivity.attach(appContext, this, getInstrumentation(), r.token, r.ident, app, r.intent, r.activityInfo, title, r.parent, config,r.referrer, r.voiceInteractor, window,);mWindow = new PhoneWindow(this, window, activityConfigCallback);
@frameworks/base/core/java/com/android/internal/policy/PhoneWindow.javamContext = context;  //PhoneWindow设置mContext为Activity里的contextmWindow.setWindowManager((WindowManager)context.getSystemService(Context.WINDOW_SERVICE), mToken, (info.flags & ActivityInfo.FLAG_HARDWARE_ACCELERATED) != 0);//context是attach传入的值，使用context创建WindowManagerif (wm == null) {  //如果wm为空则创建使用mContext创建WindowManager，mContext是PhoneWindow保存的值wm = (WindowManager)mContext.getSystemService(Context.WINDOW_SERVICE);}mWindowManager = ((WindowManagerImpl)wm).createLocalWindowManager(this);return new WindowManagerImpl(mContext, parentWindow, mWindowContextToken); //创建WindowManagerImpl，mContext是wm的，wm有两种情况mContext = context;mParentWindow = parentWindow;1. Activity 为例来分析应用窗口的添加过程
@frameworks/base/core/java/android/app/ActivityThread.java
handleResumeActivity
@frameworks/base/core/java/android/view/WindowManagerImpl.javaView decor = r.window.getDecorView();wm.addView(decor, l);
@frameworks/base/core/java/android/app/ContextImpl.javagetDisplayNoVerifyreturn mDisplay;mGlobal.addView(view, params, mContext.getDisplayNoVerify(), mParentWindow, mContext.getUserId());    //WindowManagerImpl的mContext