Window的添加过程（WMS处理部分）

基于Android U

我们知道Window的操作分为两大部分，一部分是WindowManager处理部分，另一部分是WMS处理部分。对于WMS处理部分，无论是系统窗口还是Activity，它们的Window的添加过程都会调用WMS的addWindow()方法。

addWindow()方法part1

frameworks/base/services/core/java/com/android/server/wm/WindowManagerService.java
public int addWindow(Session session, IWindow client, LayoutParams attrs, int viewVisibility,
        int displayId, int requestUserId, @InsetsType int requestedVisibleTypes,
        InputChannel outInputChannel, InsetsState outInsetsState,
        InsetsSourceControl.Array outActiveControls, Rect outAttachedFrame,
        float[] outSizeCompatScale) {
    outActiveControls.set(null);
    int[] appOp = new int[1];
    final boolean isRoundedCornerOverlay = (attrs.privateFlags
            & PRIVATE_FLAG_IS_ROUNDED_CORNERS_OVERLAY) != 0;
    int res = mPolicy.checkAddPermission(attrs.type, isRoundedCornerOverlay, attrs.packageName,
            appOp);  // 1
    if (res != ADD_OKAY) {
        return res;
    }
    ...
    synchronized (mGlobalLock) {
        if (!mDisplayReady) {
            throw new IllegalStateException("Display has not been initialialized");
        }

        final DisplayContent displayContent = getDisplayContentOrCreate(displayId, attrs.token);  // 2

        if (displayContent == null) {
            ProtoLog.w(WM_ERROR, "Attempted to add window to a display that does "
                    + "not exist: %d. Aborting.", displayId);
            return WindowManagerGlobal.ADD_INVALID_DISPLAY;
        }
        ...
        if (type >= FIRST_SUB_WINDOW && type <= LAST_SUB_WINDOW) {  // 3
            parentWindow = windowForClientLocked(null, attrs.token, false);  // 4
            if (parentWindow == null) {
                ProtoLog.w(WM_ERROR, "Attempted to add window with token that is not a window: "
                        + "%s.  Aborting.", attrs.token);
                return WindowManagerGlobal.ADD_BAD_SUBWINDOW_TOKEN;
            }
            if (parentWindow.mAttrs.type >= FIRST_SUB_WINDOW
                    && parentWindow.mAttrs.type <= LAST_SUB_WINDOW) {
                ProtoLog.w(WM_ERROR, "Attempted to add window with token that is a sub-window: "
                        + "%s.  Aborting.", attrs.token);
                return WindowManagerGlobal.ADD_BAD_SUBWINDOW_TOKEN;
            }
        }

        ...
    }
    ...
    return res;
}

WMS的addWindow()返回的是addWindow的各种状态，比如添加Window成功，无效的display等，这些状态被定义在WindowManagerGlobal中。

在注释1处根据Window的属性，调用WMP的checkAddPermission()方法来检查权限，具体在PhoneWindowManager的checkAddPermission()方法中实现，如果没有权限则不会执行后续的代码逻辑。

在注释2处通过displayId来获得窗口要添加到哪个DisplayContent上，如果没有找到DisplayContent，则返回WindowManagerGlobal.ADD_INVALID_DISPLAY这一状态，其中DisplayContent用来描述一块屏幕。

在注释3处，type代表一个窗口的类型，它的数值介于FIRST_SUB_WINDOW和LAST_SUB_WINDOW之间（1000～1999），这个数值定义在WindowManager中，说明这个窗口是一个子窗口。

在注释4处，attrs.token是IBinder类型的对象，windowForClientLocked()方法内部会根据attrs.token作为key值从mWindowMap中得到该子窗口的父窗口。接着对父窗口进行判断，如果父窗口为null或者type的取值范围不正确则会返回错误的状态。

addWindow()方法part2

frameworks/base/services/core/java/com/android/server/wm/WindowManagerService.java
public int addWindow(Session session, IWindow client, LayoutParams attrs, int viewVisibility,
        int displayId, int requestUserId, @InsetsType int requestedVisibleTypes,
        InputChannel outInputChannel, InsetsState outInsetsState,
        InsetsSourceControl.Array outActiveControls, Rect outAttachedFrame,
        float[] outSizeCompatScale) {
    ...
    synchronized (mGlobalLock) {
        ...
        final boolean hasParent = parentWindow != null;
        // Use existing parent window token for child windows since they go in the same token
        // as there parent window so we can apply the same policy on them.
        WindowToken token = displayContent.getWindowToken(
                hasParent ? parentWindow.mAttrs.token : attrs.token);  // 1
        // If this is a child window, we want to apply the same type checking rules as the
        // parent window type.
        final int rootType = hasParent ? parentWindow.mAttrs.type : type;  // 2

        boolean addToastWindowRequiresToken = false;

        final IBinder windowContextToken = attrs.mWindowContextToken;

        if (token == null) {  // 3
             if (!unprivilegedAppCanCreateTokenWith(parentWindow, callingUid, type,
                    rootType, attrs.token, attrs.packageName)) {
                return WindowManagerGlobal.ADD_BAD_APP_TOKEN;
            }
            if (hasParent) {
                // Use existing parent window token for child windows.
                token = parentWindow.mToken;
            } else if (mWindowContextListenerController.hasListener(windowContextToken)) {
                // Respect the window context token if the user provided it.
                final IBinder binder = attrs.token != null ? attrs.token : windowContextToken;
                final Bundle options = mWindowContextListenerController
                        .getOptions(windowContextToken);
                token = new WindowToken.Builder(this, binder, type)
                        .setDisplayContent(displayContent)
                        .setOwnerCanManageAppTokens(session.mCanAddInternalSystemWindow)
                        .setRoundedCornerOverlay(isRoundedCornerOverlay)
                        .setFromClientToken(true)
                        .setOptions(options)
                        .build();
            } else {
                final IBinder binder = attrs.token != null ? attrs.token : client.asBinder();
                token = new WindowToken.Builder(this, binder, type)
                        .setDisplayContent(displayContent)
                        .setOwnerCanManageAppTokens(session.mCanAddInternalSystemWindow)
                        .setRoundedCornerOverlay(isRoundedCornerOverlay)
                        .build();
            }
        }
    	... // 省略一些else if
        ...
    }
    ...
    return res;
}

注释1处通过displayContent的getWindowToken()方法得到WindowToken。

注释2处，如果有父窗口就将父窗口的type值赋值给rootType，如果没有，将当前窗口的type值赋值给rootType。

注释3处，如果WindowToken为null，则创建WindowToken。

addWindow()方法part3

frameworks/base/services/core/java/com/android/server/wm/WindowManagerService.java
public int addWindow(Session session, IWindow client, LayoutParams attrs, int viewVisibility,
        int displayId, int requestUserId, @InsetsType int requestedVisibleTypes,
        InputChannel outInputChannel, InsetsState outInsetsState,
        InsetsSourceControl.Array outActiveControls, Rect outAttachedFrame,
        float[] outSizeCompatScale) {
    ...
    synchronized (mGlobalLock) {
        ...
        final WindowState win = new WindowState(this, session, client, token, parentWindow,
                appOp[0], attrs, viewVisibility, session.mUid, userId,
                session.mCanAddInternalSystemWindow);  // 1
        if (win.mDeathRecipient == null) {  // 2
            // Client has apparently died, so there is no reason to
            // continue.
            ProtoLog.w(WM_ERROR, "Adding window client %s"
                    + " that is dead, aborting.", client.asBinder());
            return WindowManagerGlobal.ADD_APP_EXITING;
        }

        if (win.getDisplayContent() == null) {  // 3
            ProtoLog.w(WM_ERROR, "Adding window to Display that has been removed.");
            return WindowManagerGlobal.ADD_INVALID_DISPLAY;
        }

        final DisplayPolicy displayPolicy = displayContent.getDisplayPolicy();
        displayPolicy.adjustWindowParamsLw(win, win.mAttrs);  // 4
        attrs.flags = sanitizeFlagSlippery(attrs.flags, win.getName(), callingUid, callingPid);
        attrs.inputFeatures = sanitizeSpyWindow(attrs.inputFeatures, win.getName(), callingUid,
                callingPid);
        win.setRequestedVisibleTypes(requestedVisibleTypes);

        res = displayPolicy.validateAddingWindowLw(attrs, callingPid, callingUid);  // 5
        ...
        win.attach();
        mWindowMap.put(client.asBinder(), win);  // 6
        win.initAppOpsState();
        ...
        win.mToken.addWindow(win);  // 7
        displayPolicy.addWindowLw(win, attrs);
        displayPolicy.setDropInputModePolicy(win, win.mAttrs);
        ...
    }
    ...
    return res;
}

注释1处创建了WindowState，它存有窗口的所有的状态信息，在WMS中它代表一个窗口。在创建WindowState传入的参数中，this指的是WMS，client指的是IWindow，IWindow会将WMS中窗口管理的操作回调给ViewRootImpl，token指的是WindowToken。

注释2、3处分别判断请求添加窗口的客户端是否已经死亡、窗口的DisplayContent是否为null，如果是则不会再执行下面的代码逻辑。

注释4处调用了DisplayPolicy的adjustWindowParamsLw()方法，此方法会根据窗口的type对窗口的LayoutParams的一些成员变量进行修改。

注释5处检查Window是否可以被添加到系统中。

注释6处将WindowState添加到mWindowMap中。

注释7处将WindowState添加到该WindowState对应的WindowToken中（实际是保存在WindowToken的父类WindowContainer中），这样WindowToken就包含了同一个组件的WindowState。